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Mali crni sporo pokretni insekt pojavio se u kući

Mali crni sporo pokretni insekt pojavio se u kući


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U posljednjih nekoliko sedmica (zima) počeo sam primjećivati ​​ove insekte kako puze po raznim mjestima u kući.

  • Sporo se kreće kao buba.
  • Crno svuda.
  • Teško je vidjeti, ali imaju dva zupca koja vire sprijeda.
  • Posjedujem pse i mačke.
  • Živim u Tel-Avivu, Izrael.
  • Živim na drugom spratu.

Vrlo je teško snimiti sliku pa sam isprobao video. Evo gifa:

Koja je ovo vrsta?


Na temelju vanjske "ljuske" tvrdog izgleda i izduženog nosa, ovo je zasigurno vrsta bube koja se zove žižak.

S obzirom na veličinu žižaka, doba godine i lokaciju vašeg doma (drugi sprat u velikom gradu), pretpostavljam da je ovo zasigurno neka vrsta štetnika/štetočina.

Kandidati uključuju:

Pšenični žižak (Sitophilus granarius)

  • Raspon: širom svijeta
  • Hrana: pšenica, zob, raž, ječam, pirinač i kukuruz
  • Izgled: 3-5 mm dug sa izduženim njuškama; crvenkasto smeđa
  • Životna istorija: 36-254 jaja u 5-20 sedmica

Rižin žižak (Sitophilus oryzae)

  • Domet: širom svijeta
  • Hrana: pšenica, pirinač i kukuruz
  • Izgled: 2-3 mm, dug nos, smeđe/crne boje sa 4 narandžaste/crvene mrlje
  • Istorija života: 300 - 400 jaja mesečno [izvor]
  • Napomena: može letjeti

Kukuruzni žižak (Sitophilus zeamais)

  • Raspon: kosmopolitski u toplijim podnebljima [izvor]
  • Hrana: kukuruz (kukuruz), pšenica, pirinač, sirak, zob, ječam, raž, heljda, grašak, sjemenke pamuka, druge vrste skladištenih, prerađenih proizvoda od žitarica (npr. Tjestenina, manioka, druga grubo mljevena zrna), pa čak i poznato je da napada plodove dok su u skladištu (npr. jabuke)
  • Izgled: 2,5 - 4 mm, smeđe sa četiri crvenkasto -smeđe mrlje na škrinji, duga/tanka njuška i koljenaste antene
    • Pogledajte ovu stranicu Wikipedije za usporedbu pirinča i kukuruza
  • Životna istorija: 300 - 400 jaja u 36 dana

Ako ste ih viđali više, to vjerovatno znači da se razmnožavaju u nekom kontejneru sa žitaricama (možda pšenicom, pirinčem ili kukuruzom) koji imate u svom domu i mogli bi biti na dobrom putu do zaraze ako je vaš izvor žitarica velik dosta. Preporučujem da provjerite sve izvore sušene hrane u vašem domu da vidite da li čujete/vidite žižake u njoj ili kako izlaze iz posude.

S obzirom na relativno veliki broj jajašaca koje svaka ženka može snijeti i s obzirom na mjesec dana generiranja, ovo je zaraza koju želite brzo zaustaviti.

Napomena: sve informacije su sa povezanih/citiranih stranica Wikipedije osim ako nije drugačije navedeno.


Razlog blokade: Pristup s vašeg područja privremeno je ograničen iz sigurnosnih razloga.
Vrijeme: Sat, 26. juna 2021. 4:10:15 GMT

O Wordfenceu

Wordfence je sigurnosni dodatak instaliran na više od 3 miliona WordPress web lokacija. Vlasnik ove web stranice koristi Wordfence za upravljanje pristupom svojoj web lokaciji.

Također možete pročitati dokumentaciju da saznate više o Wordfence alatima za blokiranje ili posjetite wordfence.com da saznate više o Wordfenceu.

Generirano od strane Wordfence u Sub, 26 Jun 2021 4:10:15 GMT.
Vrijeme vašeg računara: .


Prisluškivani greškama? Stanovnike južne Utah pretrpali su insekti

ST. GEORGE — Mnogi stanovnici južne Jute u posljednje vrijeme su prisluškivani greškama, jer se nekoliko različitih vrsta štetočina razmnožava u velikom broju.

Zelena smrdljiva buba | Fotografija ljubaznošću Shakespeare Pest Control, St. George News

Stručnjaci kažu da se invazija insekata može pripisati kombinaciji faktora, uključujući vlažnije proljeće od prosjeka.

“Mi ’ imamo par stvari u toku. Jedan je zaista vlažna zima i proljeće koje smo imali, rekao je za St. George News Bill Heyborne, vanredni profesor biologije na Univerzitetu Southern Utah koji drži časove entomologije. “I tada smo imali nekako lagano ljetno zagrijavanje, pa su mnoge stvari ostale samo uspavane, jaja pod zemljom, takve stvari, a onda se jako brzo zagrijalo. Mislim da je kombinacija ovo dvoje dovela do mnogih izbijanja koje mi vidimo. ”

Nekoliko različitih vrsta insekata prijavljeno je širom regiona u velikom broju u posljednje vrijeme, uključujući skakavce, komarce, lažne činč bube i zelene smrdljive bube. Izvan južne Utahe, nedavno su u Idahu prijavljeni veliki rojevi “Mormonskih cvrčaka, ” vrsta katydida.

“Insekti su toliko vezani za uslove okoline, temperaturu, vlagu, dostupnost hrane, sve te stvari,” napomenuo je Heyborne. “Ponekad se zvijezde jednostavno poravnaju i uvjeti na kraju budu savršeni za određenu vrstu insekata. I tako ćete jedne godine dobiti vrlo veliku epidemiju, a zatim ih nećete vidjeti#desetljeće. Možda ih ima nekoliko tu i tamo, ali ništa posebno. A onda će se zvijezde ponovo poravnati i vi ćete ih ponovo vidjeti.”

Pogledajte rojeve insekata izvan preduzeća u St. Georgeu u videu na vrhu ovog izvještaja, zahvaljujući TW Petersen.

Što se tiče onoga što ljudi mogu učiniti u vezi s različitim greškama, Heyborne je rekao da su održive mogućnosti ograničene.

“Ako se insekti nalaze u domovima ljudi i izazivaju probleme, zaista bi trebali pozvati profesionalnog istrebljivača i riješiti to, "#8221 rekao je. “Na otvorenom, ne možemo mnogo učiniti. Mislim, ljudi bi mogli koristiti insekticide, ali često insekticidi dolaze sa svojim rizicima i svojim nuspojavama. Dakle, moja preporuka za ljude je ako su vani, ne, žao mi je#8217. Morat ćete se samo nositi s tim.

Komarci hrle do rasvjetnih tijela u rezidenciji u južnoj Juti, juli 2019. | Fotografija ljubaznošću Candice Sudweeks, St. George News

“Ako to komarci, morat ćete#nositi sredstvo protiv insekata i prikriti se. Ako skakavci i#8217 jedu vaš vrt, možda ćete morati prskati. Ali ako su samo, znate, sa strane vaše kuće ili šta već, možda ih jednostavno ostavite na miru. Ako uđu unutra, bolje pozovite istrebljivača.”

Danny Shakespeare iz Shakespeare Pest Control u St. Georgeu rekao je da je njegov posao primio mnogo poziva o rojevima zelenih smrdljivih buba u posljednjih nekoliko dana.

“Četvrtak, petak i subotu dobili smo stotine poziva u vezi s njima, a#8217 jednostavno ne možete učiniti mnogo po tom pitanju,##rekao je. “Možete nekako pomoći da ga malo ublažite, ali to nije rješenje.”

“To je više od flastera, ” objasnio je Shakespeare. “Možemo prskati i to će’ubiti gomilu njih, ali oni će samo nastaviti dolaziti.”

“Vi smo radili nešto od toga (prskanje pesticida) za neke objekte, ali to ne čini nikakvu razliku, rekao je#8221. “Na neki način to pogoršava situaciju jer se sada bave gomilom mrtvih, a onda živi još uvijek pristižu. I tako sada moraju pomesti tone mrtvih i nositi se sa svim oni živi koji dolaze. Onda će umrijeti i doći će novi val.”

Kako bi ublažio problem, Shakespeare preporučuje stanovnicima da noću isključuju svjetla i da se pobrinu da svi vanjski prozori i vrata budu zapečaćeni uklanjanjem vremenskih prilika.

Zelene smrdljive bube roje se izvan posla u St. Georgeu, Utah, juli 2019 | Fotografija ljubaznošću TW Petersen, St. George News

Zelene smrdljive bube samo su jedna od nekoliko štetočina s kojima se Shakespeare i njegovi zaposleni suočavaju, dodao je.

“Lažne greške činča su i ove godine bile jako loše,##8221 rekao je. “Bili su jako loši u proljeće, a onda su se pojavili ponovo o ovome prošle sedmice. Onda smo mi imali skakavce, a onda su komarci bili užasni. ”

Shakespeare kaže da je u većini slučajeva najbolje učiniti jednostavno sačekati štetočine dok njihov prirodni ciklus ne protekne.

“To će se morati više osušiti, a onda će jednostavno nestati, rekao je.

Lažne bube koje spominje Shakespeare viđene su u posljednje vrijeme u velikom broju u dijelovima južne Utah. Formalno poznati kao Nysius raphanus, oni su mali, vitki sivkastosmeđi insekti dugački između 1/8 inča i 1/6 inča. Mogu se agregirati u velikom broju na ili u zgradama, posebno ako se obližnje biljke domaćini beru ili obrađuju herbicidom. Oni rijetko nanose ozbiljnu štetu biljkama i bezopasni su za ljude. Prevladavajuća preporuka je da ih jednostavno tolerirate tijekom kratkog vijeka trajanja.

Horde letećih skakavaca zabilježene su i u Las Vegasu, Mesquiteu, Pahrumpu i drugim dijelovima južne Nevade, prenosi Fox 13. Mnogi su viđeni i na području Svetog Đorđa.

Heyborne je rekao da dokazi ukazuju na to da su događaji proliferacije insekata sve uobičajeniji u cijelom svijetu.

“Istini za volju, ako razgovarate sa drugim entomolozima širom svijeta, oni’vide sve više ovakvih epidemija,” rekao je. “I tako, postoji neki razgovor o tome, da li je ovo povezano sa klimatskim promjenama ili ne? Ne znamo odgovor na to pitanje. Ali pretpostavljam da će vrijeme pokazati.”


Obuka o uzgoju cvrčaka

Evo nekih informacija o biologiji kriketa. Razumijevanje biologije cvrčaka pomoći će vam u rješavanju mnogih problema na koje možete naići. Gornji video daje još neke savjete.

Cvrčci su insekti koji pripadaju redu Orthoptera i porodice Gryllidae (pravi cvrčci). Općenito su svejedi, jedu i biljnu i životinjsku tvar. Više temperature će im skratiti životni vijek, ali će povećati brzinu rasta.

Naše iskustvo odnosi se na uzgoj običnog kućnog cvrčka (Acheta domesticus) međutim sve metode koje opisujemo mogu se jednako lako koristiti i za druge vrste.

Životni ciklus

Cvrčak obično dostiže seksualnu zrelost oko 5-6 nedelja u zavisnosti od umerenih uslova i uslova sredine. Kratak životni ciklus cvrčka znači da morate stalno proizvoditi mlade cvrčke da biste održali koloniju. Ukratko, kućni cvrčak (najčešće čuvane vrste) ima sljedeći životni ciklus:

  1. Mužjak aktivno traži ženku ili privlači ženku cvrkutavim zvukom trljanjem nazubljenih rubova prednjih krila (stridulacija). Brzo cvrkutanje se čuje kad mu se približi prijeteći mužjak, a sporije cvrkutanje kako bi se ženka namamila na parenje.
  2. Dolazi do parenja i mužjak oplođuje ženska jaja. Ženka polaže jaja oko 1 cm u vlažnu zemlju ili organski materijal. Kad su uvjeti za to pogodni, kućni cvrčak može polagati jaja svake druge sedmice tokom svog odraslog života. Produktivne ženke mogu snijeti približno 200 jaja u šarži. Jaja su bjelkaste/žute boje i dugačka oko 2-3 mm. Ženka cvrčka može proizvesti oko 600 ili više jaja tokom svog života.
  3. Jaja se izlegnu približno 11-14 dana kasnije kada se uzgajaju na oko 30 stepeni Celzijusa (86 stepeni Fahrenheita). Mladunci su dugački otprilike 2-3 mm i male su replike svojih roditelja koje se nazivaju pinheads ili nimfe.
  4. Kako cvrčci rastu, oni moraju da skinu kožu (linjaju) u nekoliko faza nimfe. Cvrčak koji se istopio je bijele/žute boje i može se jesti sve dok se njegov egzoskelet (vanjsko kućište) ne stvrdne (pogledajte donju fotografiju desno).
  5. Mlade glavice brzo rastu, redovito gube kožu. Faze rasta cvrčka su:
  • Glave igle (dužine 2-3 mm)
  • Mali cvrčci (do 10 mm dužine tela)
  • Srednje (10 do 20 mm dužine tela)
  • Veliki (dužina tela 20-30 mm)

LIJEVO- Srednji kriket s lijeve strane, veliki cvrčak s desne strane.
DESNO- Stari egzoskelet s lijeve strane, tek istopljeni cvrčak s desne strane

Kao što je gore prikazano, razlika između srednjih i velikih cvrčaka je kada dobiju sjajna krila i jajoložac.

Temperature

Cvrčci su egzotermni (hladnokrvni) i nisu u stanju podići tjelesnu temperaturu kako bi optimizirali rast ili kretanje. Komercijalni proizvodni sistemi održavaju brze stope rasta održavajući optimalne uslove okoline, uravnoteženu ishranu i stroge higijenske standarde. To će spriječiti da bolesti i štetočine utječu na koloniju.

Iako mogu preživjeti niz temperatura, najbolje se razmnožavaju i rastu kada su temperature stalno u rasponu od 90-95 stepeni Celzijusa (30-35 stepeni Celzijusa). Cvrčci su noćni u divljini, iako su u zatočeništvu aktivni u svako doba dana i ne zahtijevaju osvjetljenje.

Ponašanje

U komercijalnoj situaciji, stotine cvrčaka smješteno je u neposrednoj blizini. Ova neprirodna situacija će rezultirati ili borbama ili značajnim kanibalizmom osim ako se ne ispune njihovi osnovni zahtjevi. Stoga je od suštinskog značaja da adekvatna hrana i voda budu dostupni u svakom trenutku u kombinaciji s puno skrovišta za životinje koje mogu pobjeći jedna od druge. Najugroženiji su mladi cvrčci i nedavno saljene životinje (žuta koža). Opcije upravljanja i dizajna za smanjenje kanibalizma navedene su u našim priručnicima. Cvrčci su noćne prirode i ne zahtijevaju osvjetljenje.

Izbor vrsta

Širom svijeta brojne vrste cvrčaka se uzgajaju komercijalno, međutim, najčešće tri vrste su: 1) kućni cvrčak (Acheta domesticus ili domestica u nekim publikacijama) 2) Crni cvrčak (Gryllus bimaculatus) i 3) novi jamajkanski poljski cvrčak otporan na viruse (Gryllus assimilis).

Kućni kriket (Acheta domesticus)

Kućni kriket (Acheta domesticus ili domestica u nekim je publikacijama) najpopularnija vrsta koja se koristi u komercijalnoj proizvodnji u većini dijelova svijeta. (Pogledajte fotografiju). Također se uobičajeno uzgaja za prehranu ljudi. To je zbog velike produktivnosti i sposobnosti rukovanja širokim spektrom okruženja.

Poznat je i kao "evropski cvrčak" ili "braon kućni cvrčak". Smatra se da vrsta potječe iz jugozapadne Azije, no proširila se u većinu zemalja svijeta trgovinom kućnih ljubimaca ili slučajno transportnim teretom. Ova vrsta dobila je uobičajeno ime zbog navike da živi u kućama kako bi izbjegla niske zimske temperature. Ova vrsta je tipično sive ili smeđe boje.

Evropski kućni kriket, (Acheta domestica)

Produktivne ženke mogu snijeti otprilike 200 jaja u šarži i sposobne su polagati šaržu svakih nekoliko tjedana. Kućni cvrčak općenito je izdržljiva vrsta koja dobro putuje ako se pravilno zapakira i dobro je prilagođena komercijalnoj proizvodnji. Podaci navedeni u ovom priručniku odnose se na iskustvo stečeno uzgojem kućnog cvrčka, koji bi se uglavnom mogao koristiti za druge vrste, poput crnog cvrčka.

Nedavno se virus poznat kao virus paralize kriketa proširio iz Evrope u SAD. Virus utječe samo na Acheta domesticus (kućni cvrčak) i uzrokovao je smrt cvrčaka na mnogim farmama insekata. Na sreću ova je bolest sigurna za životinje ili ljude.

Zanimljivo je da neki od velikih uzgajivača cvrčaka s kojima razgovaramo nisu bili pogođeni i imali su dobre higijenske metode i metode upravljanja bolestima. Nažalost mjere za suzbijanje ovog virusa na drugim farmama bile su uglavnom nedjelotvorne i mnogi uzgajivači cvrčaka prešli su na virus otporan na Gryllus assimilis (jamajkanski poljski cvrčak). Kućni cvrčak se još uvijek često uzgaja širom svijeta, ali u nekim dijelovima SAD-a možete vidjeti da se prodaje više jamajčanskih poljskih cvrčaka.

Crni cvrčak (Gryllus bimaculatus)

Druga vrsta koja se komercijalno uzgaja širom svijeta je crni cvrčak (Gryllus bimaculatus- pogledajte donju fotografiju). Ova vrsta je poznata i kao "crni cvrčak" ili "afrički/mediteranski cvrčak". Postoje mnoge vrste crnih cvrčaka, a u nekim zemljama se uzgajaju i druge blisko srodne autohtone vrste. Na primjer u Australiji Teleogryllus commadus se povremeno uzgaja. U divljini se mladi izlegu u proljeće i hrane se širokim spektrom sjemena, biljaka, insekata ili životinjskih proizvoda. Boja ove vrste može varirati od mlazne, smeđe ili crvene, ovisno o vrsti. Poput kućnog cvrčka, oni su svejedi koji jedu biljne i životinjske ostatke.

Cvrčak na crnom polju (Gryllus bimaculatus). Fotografija: Mitteleer Feldgrille

Boja ove vrste može varirati od crne do smeđe, smeđe ovisno o vrsti. Poput kućnog cvrčka, oni su svejedi koji jedu biljne i životinjske ostatke. Ženka može položiti oko 2.000 jaja tokom svog života.

Poređenje vrsta

Crni cvrčci su nešto osjetljiviji tokom tranzita i zahtjevniji su u svojim higijenskim i uzgojnim zahtjevima. Nešto su veći sa tijelom od 3-4 cm (1,18-1,57 inča) i općenito ih je teže probaviti od kućnog cvrčka zbog hitinoznih (tvrdih zaštitnih tvari) grudnog koša i krila. Domaći cvrčak je manji, približne veličine tijela 2-3 cm (0,79-1,18 inča).

Da biste smanjili utjecaj uvođenja stranih vrsta, razmislite o korištenju vrsta koje su autohtone u vašem lokalnom području. Mnoge zemlje imaju autohtone vrste poljskog cvrčka koje su općenito dobro prilagođene za proizvodnju. Ovo je također dobra strategija kada vaš komercijalni dobavljač ima insekte koji pokazuju znakove bolesti ili genetski inbriding (deformitete, slab imunitet na bolesti itd.). Budući da su ove vrste iz divljine, općenito imaju dobru genetsku raznolikost. Iako je rizik od bolesti nizak, možda ćete ih htjeti staviti u karantenu na neko vrijeme kako biste provjerili ne nose li bolesti ili štetočine.

Kako će vam u početku trebati lokalni dobavljač, a povremeno će vam trebati i dodatne zalihe za poboljšanje genetike, preporučuje se kupovina vrste koju je lako nabaviti od drugih komercijalnih uzgajivača u vašem području.

Sada kada znate malo više o tome zašto cvrčci otkucavaju, u sljedećoj lekciji ćemo pogledati kako ih uzgajati.

Imamo još mnogo toga za naučiti, međutim ako danas želite početi uzgajati cvrčke, možete odmah preuzeti knjigu i video zapise na našoj stranici „Proizvodi“.


Rezultati

Eksperiment rotacije diska

Izveli smo 15 uspješnih eksperimenata rotacije diska. Diskovi su rotirani prosječno 305 ° (raspon: 71–641 °), a rakovi su kompenzirali u prosjeku 92 ± 7,0%rotacije diska. Ovi rezultati su sažeti u Tabeli 2. Rakovi sa dobrom kompenzacijom imali su tendenciju da više rotiraju disk, budući da je cilj bio da ih preorijentišu, a ne da posmatraju njihov odgovor na standardizovanu rotaciju diska. Zanimljivo je da su rakovi često nastavili da se rotiraju u suprotnom smeru nakon što se disk zaustavio, kao što se vidi na slikama 3 i 5. Međutim, to nije bilo zato što su imali informacije o eksternom kompasu, jer su ti rakovi obično završili u nedostatku kompenzacije, što se ne bi dogodilo da orijentirali su se prema vanjskom znaku. U prosjeku, rakovi su kompenzirali za 21,4±20,6° nakon zaustavljanja diska, što je bilo ekvivalentno 7,7±9,6% njihove ukupne kompenzacije.

Sažetak rezultata svih 15 ispitivanja, uključujući grešku u orijentaciji rakova kada se disk počeo rotirati, nametnutu rotaciju diska, optomotornu kompenzaciju i grešku u navođenju proizvedenih putem sedam potencijalnih mehanizama integracije putanje

. . . . Greška u nalaženju. . . . . . .
Suđenje. Početna greška. Disk. Naknada. Crna. Plava. Violet . Crveno. Narandžasta. Zeleno. Siva .
1 —5.0 482 480 —3.7 —6.8 —9.5 —5.8 41.9 49.6 —6.2
2 —22.5 298 266 —36.7 —41.6 —27.0 2.0 —63.1 —58.3 5.4
3 5.6 497 434 —49.8 —90.8 —38.2 9.4 61.1 47.3 —37.4
4 —16.7 227 186 —52.5 —102.7 —33.7 16.9 —178.9 —166 27.6
5 —6.4 440 429 —9.8 —11.7 —13.6 —16.3 —32.0 —32.5 —16.2
6 8.1 641 617 —10.6 —7.6 —5.0 —15.0 —39.2 —38.9 —1.2
7 13.6 122 121 —3.5 —5.4 —3.6 27.4 99.2 105.7 31.5
8 0.4 283 254 —28.9 —35.4 —11.8 32.9 —103.4 —100.8 38.4
9 —5.9 139 123 —20.2 —25.6 —8.2 6.0 107.0 113.7 5.5
10 15.3 311 305 —7.1 —7.7 —7.8 —7.0 —44.8 —44.0 —8.1
11 4.8 101 89 —3.1 0.7 —0.9 1.4 66.0 60.0 0.2
12 0.7 595 574 —16.6 —12.4 —16.0 —6.9 —76.3 —84.9 —9.8
13 22.5 204 177 —27.9 —46.1 —29.3 7.9 164.5 165.9 —7.0
14 —24.5 166 141 —28.9 —47.5 —34.9 —17.1 139.2 163.4 —12.5
15 16.5 71 54 —8.3 —24.8 —41.1 —9.4 76.2 97.6 —4.5
. . . . Greška pri pokretanju. . . . . . .
Suđenje . Početna greška. Disk . Naknada. Crna . Plava. Violet. Crveni . Narandžasta. Zeleno. Siva .
1 —5.0 482 480 —3.7 —6.8 —9.5 —5.8 41.9 49.6 —6.2
2 —22.5 298 266 —36.7 —41.6 —27.0 2.0 —63.1 —58.3 5.4
3 5.6 497 434 —49.8 —90.8 —38.2 9.4 61.1 47.3 —37.4
4 —16.7 227 186 —52.5 —102.7 —33.7 16.9 —178.9 —166 27.6
5 —6.4 440 429 —9.8 —11.7 —13.6 —16.3 —32.0 —32.5 —16.2
6 8.1 641 617 —10.6 —7.6 —5.0 —15.0 —39.2 —38.9 —1.2
7 13.6 122 121 —3.5 —5.4 —3.6 27.4 99.2 105.7 31.5
8 0.4 283 254 —28.9 —35.4 —11.8 32.9 —103.4 —100.8 38.4
9 —5.9 139 123 —20.2 —25.6 —8.2 6.0 107.0 113.7 5.5
10 15.3 311 305 —7.1 —7.7 —7.8 —7.0 —44.8 —44.0 —8.1
11 4.8 101 89 —3.1 0.7 —0.9 1.4 66.0 60.0 0.2
12 0.7 595 574 —16.6 —12.4 —16.0 —6.9 —76.3 —84.9 —9.8
13 22.5 204 177 —27.9 —46.1 —29.3 7.9 164.5 165.9 —7.0
14 —24.5 166 141 —28.9 —47.5 —34.9 —17.1 139.2 163.4 —12.5
15 16.5 71 54 —8.3 —24.8 —41.1 —9.4 76.2 97.6 —4.5

Inicijalna greška, greška u orijentaciji rakova kada se disk počeo okretati Disk, nametnuta kompenzacija rotacije diska, kompenzacija optomotora.

Ispitivanja prikazana na slikama 3, 4, 5 su u redovima 1-3, redom.

Sve vrijednosti su u stupnjevima.

Primjer ispitivanja u kojem je rak u potpunosti kompenzirao rotaciju diska. (A) Poprečna os tijela rakovog tijela (umetnuta), digitalizirana u intervalima od 200 ms, prikazana od početka rotacije diska do rakova do kuće. Brojevi su u sekundama nakon početka rotacije. Veliki zatamnjeni krug, bijeli krug rotirajućeg diska, položaj rakova kada je rotacija diska započela plavi krug, položaj rakova kada je disk prestao. (B) Orijentacija i nošenje rakova i diska tokom vremena. Pretpostavljalo se da je kompenzacijska rotacija tijela rakom prestala u vrijeme označeno crnom strelicom. Obratite pažnju na sličnost ove orijentacije tijela s onom na početku eksperimenta. (C) Ugaona brzina kraba i diska i ugaona brzina kraba u odnosu na disk tokom vremena. (D) Rekonstrukcija sedam mogućih kućnih vektora izračunatih od strane integratora putanje, superponiranih na stvarnu putanju raka kao u A. Pogledajte tekst za detalje.

Primjer ispitivanja u kojem je rak u potpunosti kompenzirao rotaciju diska. (A) Poprečna os tijela rakovog tijela (umetnuta), digitalizirana u intervalima od 200 ms, prikazana od početka rotacije diska do rakova do kuće. Brojevi su u sekundama nakon početka rotacije. Veliki zatamnjeni krug, bijeli krug rotirajućeg diska, položaj rakova kada je rotacija diska započela plavi krug, položaj rakova kada je disk prestao. (B) Orijentacija i držanje raka i diska tokom vremena. Pretpostavlja se da je kompenzacijska rotacija tijela od strane raka prestala u vrijeme označeno crnom strelicom. Uočite sličnost ove orijentacije tijela s onom na početku eksperimenta. (C) Ugaona brzina kraba i diska i ugaona brzina kraba u odnosu na disk tokom vremena. (D) Rekonstrukcija sedam mogućih kućnih vektora izračunatih od strane integratora putanje, superponiranih na stvarnu putanju raka kao u A. Pogledajte tekst za detalje.

Primjer ispitivanja u kojem je rak premalo kompenzirao rotaciju diska i imao je značajno samoprevođenje tokom rotacije diska. (A) Poprečna os tijela raka digitalizirana u intervalima od 200 ms, kao na slici 3. (B) Orijentacija i orijentacija raka i diska tokom vremena. Crne strelice, dva nagla kompenzacijska zaokreta koja su se dogodila nakon prestanka rotacije diska, od kojih je druga u sredini povratka bilježi podudarnu veliku promjenu u ležaju, uzrokovanu trčanjem kući. (C) Ugaona brzina kraba i diska i ugaona brzina kraba u odnosu na disk tokom vremena. (D) Rekonstrukcija sedam mogućih domaćih vektora koje je izračunao integrator puta, postavljeni na stvarnu putanju rakova kao u A. Vidi tekst za detalje.

Primjer ispitivanja u kojem je rak premalo kompenzirao rotaciju diska i imao je značajno samoprevođenje tokom rotacije diska. (A) Rakova poprečna os tijela digitalizirana u intervalima od 200 ms, kao na slici 3. (B) Orijentacija i nošenje rakova i diska tokom vremena. Crne strelice, dva nagla kompenzacijska zaokreta koja su se dogodila nakon prestanka rotacije diska, od kojih je druga u sredini povratka bilježi podudarnu veliku promjenu u ležaju, uzrokovanu trčanjem kući. (C) Ugaona brzina kraba i diska i ugaona brzina kraba u odnosu na disk tokom vremena. (D) Rekonstrukcija sedam mogućih domaćih vektora koje je izračunao integrator puta, postavljeni na stvarnu putanju rakova kao u A. Vidi tekst za detalje.

Pomno ćemo ispitati tri eksperimenta rotacije. Ovo troje je odabrano zbog njihove sposobnosti da ilustriraju važne tačke, ne nužno zbog toga što se pridržavaju bilo kojeg određenog ishoda. Slika 3 je prvi takav primjer. Poprečna os tijela rakova označena je strelicom koja pokazuje na stranu rupe (vidi sliku 3. Umetnuti dio), digitalizirana je jednom u sekundi, a prikazuje se od početka rotacije diska sve dok rak nije stigao kući. Disk se rotirao u smjeru suprotnom od kazaljke na satu za 482 ° tokom 11 s, ali rak je to aktivno kompenzirao (uporedite orijentaciju tijela i diska na slici 3B, ili kutnu brzinu rakova i diska na slici 3C) i nastavio je to raditi 5 s nakon prestanka rotacije diska. Za ove i druge rakove koji su nastavili nadoknađivati ​​nakon zaustavljanja diska, bilo je uobičajeno da to rade u prilično naglim zavojima, kao što se vidi na t= 15 s na slici 3B, C. Imajte na umu da je nakon ovog skretanja orijentacija rakova dosegla manje -više stabilno stanje. Stoga smo tada, označeni vertikalnom strelicom na slici 3B, utvrdili da je rak završio kompenzaciju. Podkompenzacija raka je, dakle, početna orijentacija minus orijentacija u t= 16 s, au ovom slučaju je ∼1 °, što znači da je ovaj rak kompenzirao gotovo svu rotaciju diska.

Unatoč savršenoj kompenzaciji, ovaj rak je malo promašio dom i pronašao ga tek nakon kratke potrage. Zašto je ovaj rak propustio dom? Rekonstruisani kućni vektori na slici 3D daju trag. Način procjene ovih puteva je zabilježiti koji se domaći vektori približavaju vlastitoj putanji navođenja rakova, označenoj cijan (svijetlo plavom) strelicom. Pretpostavke na kojima se zasnivaju ti putevi trebaju se privremeno prihvatiti kao konzistentne s mehanizmom integracije pravog puta, dok treba smatrati da one staze koje se uvelike razlikuju od promatranog imaju pretpostavke koje su suprotne pravom mehanizmu. Na primjer, zelena i narandžasta su jedini putevi za integraciju kompenzacijskih zavoja, a činjenica da se oba razlikuju od promatrane putanje pod velikim uglom baca sumnju na ideju da pravi mehanizam integrira ove zavoje. Ljubičasta staza pretpostavlja da rak može integrirati svoje apsolutno kretanje, što bi se moglo postići integracijom njegovog kutnog i linearnog momenta. Međutim, rakovi guslači očigledno nemaju sposobnost da integrišu nametnuti prevod koristeći zamah ili bilo koji drugi znak (Zeil, 1998 Cannicci et al., 1999 Layne et al., 2003). Dakle, ljubičasti kućni vektor odstupa od posmatrane putanje navođenja za ugao koji zavisi od količine koju je rak preorijentisao i pomerio.

Preostala četiri puta se ne razlikuju po svojoj točnosti iz dva razloga. Prvo, rak se nije mnogo sam prevodio dok se disk rotirao, što je otežavalo razlikovanje između crvene i sive opcije, te crne i plave. Drugo, zbog odlične rotacijske kompenzacije ove osobe, nismo je uspjeli preusmjeriti, što otežava razlikovanje idiotetičkih i alotetičkih opcija koje ne integriraju optomotoriku. Zapravo, ovaj rezultat ne rješava čak ni pitanje smjera kompasa. To, međutim, pokazuje da veliki dio samo-lokomocije, u obliku ∼480° kompenzacijske rotacije, nije doprinio pravom kućnom vektoru. Zbog savršene kompenzacije ove rakovice i nedostatka samoprevođenja, naš se eksperiment svodio na pasivni prijevod. Ovaj je rak promašio kuću u smjeru i udaljenosti koju je pasivno preveo disk.

Što se događa kada rakovi ne kompenziraju u potpunosti rotaciju diska? Naš drugi primjer, ilustrovan na slici 4, pokazuje raka koji je doživio rotaciju diska u smjeru suprotnom od kazaljke na satu od 298° tokom 7,8 s. Za razliku od prethodnog primjera, pokušao se vratiti kući odmah nakon što je disk stao, a tada je ostao nedovoljno kompenziran za rotaciju diska za 32 °. Otprilike za ovaj iznos je nedostajao kući. Jedina varijabla koju crni, plavi i ljubičasti vektori dijele – a ne dijele sa crvenim i sivim vektorima, koji se oba blisko podudaraju sa pravom početnom putanjom – je da se njihova komponenta smjera mjeri u odnosu na neki alotetički znak. To sugerira da rak nije koristio znakove alotetskih smjerova. Slaba preciznost narančastog i zelenog vektora opet sugerira da rak nije integrirao svoju kompenzacijsku rotaciju. Sličnost crvenog i sivog vektora (te plavog i crnog vektora) posljedica je činjenice da je ovaj rak još jednom napravio malo samoprevođenja tijekom rotacije diska. Sveukupno slika 4 bila je najčešći tip ishoda iz naših eksperimenata, unatoč činjenici da je nekoliko rakova bilo vrlo blizu istaknutih znamenitosti koje su ih mogle voditi. U jednom slučaju mala mladica mangrove smještena ∼1 cm od ulaza u jazbinu očito nije pružila nikakav smjerni znak za rakova koji je rotirao samo 9 cm dalje, i promašio je dom za 26°, gotovo tačno za iznos za koji je nedovoljno kompenzirao (27°) . Rakovica na slici 4 je na kraju ponovo ušla u svoju rupu, ali je to učinila vodeći suprotnu stranu tijela od normalne. Rakovi obično ulaze u svoje jazbine vodeći sa stranom tijela koja je okrenuta prema jazbini tokom njihovog hranjenja. Do vođenja sa suprotne strane dolazilo je vrlo rijetko, općenito nakon eksperimentalne manipulacije zbog koje je rak izgubio svoju rupu.

Primjer ispitivanja u kojem je rak premalo kompenzirao rotaciju diska i imao je malo samoprevođenja tijekom rotacije diska. (A) Poprečna os tijela raka digitalizirana u intervalima od 200 ms, kao na slici 3. (B) Orijentacija i orijentacija raka i diska tokom vremena. Kompenzacijska rotacija tijela prestala je kada se disk zaustavio, a rak se odmah nakon toga udomio. (C) Ugaona brzina kraba i diska i ugaona brzina kraba u odnosu na disk tokom vremena. (D) Rekonstrukcija sedam mogućih kućnih vektora izračunatih od strane integratora putanje, superponiranih na stvarnu putanju raka kao u A. Pogledajte tekst za detalje.

Primjer ispitivanja u kojem je rak premalo kompenzirao rotaciju diska i imao je malo samoprevođenja tijekom rotacije diska. (A) Poprečna os tijela raka digitalizirana u intervalima od 200 ms, kao na slici 3. (B) Orijentacija i orijentacija raka i diska tokom vremena. Kompenzacijska rotacija tijela prestala je kada se disk zaustavio, a rak se odmah nakon toga udomio. (C) Ugaona brzina rakova i diskova i ugaona brzina rakova u odnosu na disk tokom vremena. (D) Rekonstrukcija sedam mogućih domaćih vektora koje je izračunao integrator puta, postavljeni na stvarnu putanju rakova kao u A. Vidite tekst za detalje.

Naš treći primjer, ilustrovan na slici 5, prikazuje raka čiji je disk rotiran za 497° preko t= 8 s, ali kompenzirano za sve rotacije diska osim 63 °. Kao na slici 3, ova osoba je napravila dva nagla kompenzacijska zaokreta nakon što se disk zaustavio kako bi se preorijentirao, uključujući jedan usred povratka u blizini t=16 s (vidi vertikalne strelice na slici 5B,C). Za tačku konačne nadoknade iskoristili smo početak povratka kući blizu t= 12 s. Ovaj primjer je uključen jer nam značajan samoprevođenje rakova tokom rotacije diska omogućava da procijenimo je li to vjerovatno bilo integrirano. Imajte na umu da je crveni vektor blizu prave putanje navođenja, ali sivi vektor značajno odstupa od njega. Jasno je da barem u ovom slučaju samoprevođenje nije bilo integrirano, već je vjerovatno bilo nenamjeran dio kompenzacijskog odgovora.

Da bismo dobili sliku odgovora općenito, uporedili smo smjerove početnih vektora modela sa uočenim smjerovima navođenja (slika 6), pri čemu su potonji izvedeni iz nagiba linije linearne regresije koja odgovara povratnoj putanji rakova . Svi su podaci normalizirani na rotaciju diska u smjeru suprotnom od kazaljke na satu i iscrtani u jediničnim polarnim koordinatama u odnosu na promatrani smjer navođenja, koji je postavljen na 0 ° (vidi sliku 6A). Ovdje se obrađuje samo smjer povratne putanje, a ne točna lokacija na koju rakovi pokušavaju doći, jer je određivanje lokacije kraja domaćeg vektora mnogo manje precizno od određivanja njegovog smjera. Pokazano je da su smjerovi povratka svih alotetički izmjerenih kućnih vektora (sl. 6B–D) značajno u smjeru kazaljke na satu posmatrane putanje navođenja. Ovo je za očekivati ​​ako je većina rakova nedovoljno kompenzirala rotaciju diska do određenog stepena i napravila grešku navođenja pod istim ili sličnim uglom.

Usporedba tačnosti navođenja sedam modela integracije putanje, tj. kut greške između vektora modela i promatranog smjera navođenja, kako je prikazano u (A). Polar plots are for counter-clockwise disk rotation and show the mean error angle (θ) plotted with respect to the observed homing direction (set to 0°). Values are ±95% confidence intervals r is the mean vector length. (B–D) exocentric paths,(E–H) egocentric paths, (I,J) the smaller of the absolute error values between (I) black and blue and (J) red and gray paths. See text for details.

Comparison of the homing accuracy of the seven path-integration models,i.e. the error angle between the model vector and the observed homing direction, as illustrated in (A). Polar plots are for counter-clockwise disk rotation and show the mean error angle (θ) plotted with respect to the observed homing direction (set to 0°). Values are ±95% confidence intervals r is the mean vector length. (B–D) exocentric paths,(E–H) egocentric paths, (I,J) the smaller of the absolute error values between (I) black and blue and (J) red and gray paths. See text for details.

The return directions of idiothetically measured vectors that include compensatory turns (Fig. 6F,G)are nearly randomly dispersed, strongly indicating that fiddler crabs distinguish between compensatory turns and those that are non-compensatory. The red and gray vectors (Fig. 6E,H) are centered very closely around the homing direction, with the red having slightly tighter clustering. This result, along with the clockwise bias of the black, blue and violet paths, explicitly addresses whether the spatial frame of reference used for computing the home vector is exocentric or egocentric, regardless of whether it was compiled from path integration or not: an exocentric vector should not change when an animal is turned on the spot (Benhamou,1997). However, the home vector of these crabs rotated by almost exactly the amount that we reoriented them. The average under-compensation by all crabs was 21.8±16.1° (calculated from data shown in Table 2), which is very close to the direction of the mean vector in Fig. 6I, i.e. 19.9±9.3°. This confirms that fiddler crabs have an egocentric frame of reference, and that they utilize idiothetic direction information, but it leaves open the question of whether or not self-translation observed during disk rotation was intentional (and integrated). This question is not central to our main conclusions, but we did notice that in all but one experiment, when the red vector did not closely match the observed homing path, the gray vector did, and obrnuto. We have therefore plotted the smaller of the absolute error angles between red and gray, and between black and blue, the allothetic pairs which differ only in their integration of self-translation(Fig. 6I,J). The allothetic mean angle remained significantly different from the observed homing direction, while the idiothetic remained statistically indistinguishable from the observed homing direction. Fig. 6J did produce a plot with tighter clustering, but the mean angle was slightly larger than in Fig. 6E,H. Therefore the question of whether self-translation on the disk was intentional and integrated or not remains unanswered. But the comparison with Fig. 6I does lend further support to the notion that the crabs utilized idiothetic rather than allothetic direction information.

The control of body turning was investigated by computing the cross-correlation coefficient between potential inputs and outputs of the control system, at different time lags. We used only the time periods during which compensation was active. We found that the correlation was highest(r=0.68) between egocentric crab angular velocity (i.e. relative to the disk) and disk angular velocity, but this was at zero lag, which is not indicative of a causal relationship (Fig. 7). However, this correlation with disk angular velocity was higher over all lags than that with body orientation (which peaks at r=0.51), or with orientation error (r=0.53 orientation error = bearing minus orientation see Zeil, 1998). When combined with other data presented here, this result suggests that compensatory rotation is induced by the disk angular velocity, as sensed either visually or vestibularly. This is in contrast to what Zeil(1998) found for U. l. annulipes, where the highest correlation was between crab angular velocity and body orientation, at a lag of 40 ms. We address this difference between our results and Zeil's in the Discussion.

Examination of the input–output relationships of the crab's compensatory rotation on the disk. Means (solid lines) and s.d. (broken lines) of time-lagged cross-correlations for all 15 trials, between:crab egocentric and disk angular velocities (sign reversed, blue line with circles) crab egocentric angular velocity and crab orientation (sign reversed, red line with triangles) crab egocentric angular velocity and orientation error (this is affected by both rotation and translation black line with squares). Positive lags indicate disk angular velocity, crab orientation or orientation error leading in time, negative lags indicate crab egocentric angular velocity leading.

Examination of the input–output relationships of the crab's compensatory rotation on the disk. Means (solid lines) and s.d. (broken lines) of time-lagged cross-correlations for all 15 trials, between:crab egocentric and disk angular velocities (sign reversed, blue line with circles) crab egocentric angular velocity and crab orientation (sign reversed, red line with triangles) crab egocentric angular velocity and orientation error (this is affected by both rotation and translation black line with squares). Positive lags indicate disk angular velocity, crab orientation or orientation error leading in time, negative lags indicate crab egocentric angular velocity leading.

Slippery patch experiment

The results described so far in this paper make clear that a fiddler crabs'home vector is coded egocentrically using idiothetic spatial information. However, there are few clues as to the sensory modes involved. Here, we attempt to determine how fiddler crabs measure distance, using an experiment that distinguishes two categories of sensory cue. The first category consists of cues that could only be derived from real movement over the ground, such as optic flow and vestibular signals. The second category consists of cues that we could experimentally dissociate from real body movement by use of a substrate on which the crabs slipped (the slippery patch), such as proprioceptors and central motor commands.

The experiment consisted of maneuvering a slippery patch of wet acetate between a foraging crab and its burrow. When crabs were scared from above,they ran across the patch, and, as it turned out, individuals either slipped and stopped briefly short of home, or did not slip and ran directly to their burrow. Slipping was characterized qualitatively by cartoon-like running-without-moving behavior, and quantitatively by a depression of running velocity while on the patch. The rationale behind this experiment was that, if crabs measured the distance of their return home by means of cues that are derived from movement with respect to the ground such as, for instance, optic flow, then they should return directly home whether they slipped or not. If they slipped they might take longer, but, like crabs that did not run over a patch, they would not stop short of home. Since bees (and, possibly, desert ants) can measure distance using optic flow(Wehner, 1992 Esch and Burns, 1995, 1996 Ronacher and Wehner, 1995 Srinivasan et al., 1996 Esch et al., 2001 but see Ronacher et al., 2000), this was obviously a reasonable possibility. On the other hand, if crabs measured the distance of their return home by means of proprioceptive cues, then those crabs that slipped should `play out' their home vector, and stop sooner than control crabs who did not slip or who did not run over the patch. Proprioceptive input from the legs might be a measure of `effort over time' or some measure of motor output that, at its crudest, might be `number of steps'. Thus, in this second category of cues, but not in the first, slipping crabs should stop before reaching home.

One example of such an experiment is shown in Fig. 8, in which the crab was scared when it was 30 cm from home. After a few initial steps, the crab stopped running when it reached the front edge of the patch (this was the only individual to do so), but then proceeded to run across the patch, and stopped 7 cm before reaching home (at large gray arrow, Fig. 8A). The qualitative observation of slipping by this crab was confirmed by the fact that its average running velocity on the patch was 16.8 cm s -1 (Fig. 8B), which is much lower than normal escape velocity, around 70 cm s -1 among controls (see Fig. 9B).

Example of a slippery patch experiment. (A) The crab was frightened when situated at `start', ran over the slippery patch (gray rectangle), and stopped at the filled arrow, before finding its way home. (B) Plot of crab running velocity against distance run. The shaded area indicates when the crab was on the slippery patch.

Example of a slippery patch experiment. (A) The crab was frightened when situated at `start', ran over the slippery patch (gray rectangle), and stopped at the filled arrow, before finding its way home. (B) Plot of crab running velocity against distance run. The shaded area indicates when the crab was on the slippery patch.

Running velocity of escaping crabs. (A) Running velocity plotted against relative distance home (d/D). Red lines, crabs that ran over the patch and stopped before reaching home blue lines, crabs that ran over the patch but did not stop before reaching home black lines, control crabs that did not run over a patch. Red and blue lines are solid where the crabs were on the patch. (B) Mean of running velocity profiles plotted against relative distance home (d/D). Controls (including both no-patch and non-slippers), black line slippers, red line lines are mean running velocity ± s.d. (dotted lines). (C) Mean of running velocity profiles of controls (no patch, black line) and non-slippers (blue line) plotted against relative time until first stop (t/T)lines are mean running velocity ± s.d. (dotted lines). (D)Same data as in B but plotted against relative time until first stop(t/T).

Running velocity of escaping crabs. (A) Running velocity plotted against relative distance home (d/D). Red lines, crabs that ran over the patch and stopped before reaching home blue lines, crabs that ran over the patch but did not stop before reaching home black lines, control crabs that did not run over a patch. Red and blue lines are solid where the crabs were on the patch. (B) Mean of running velocity profiles plotted against relative distance home (d/D). Controls (including both no-patch and non-slippers), black line slippers, red line lines are mean running velocity ± s.d. (dotted lines). (C) Mean of running velocity profiles of controls (no patch, black line) and non-slippers (blue line) plotted against relative time until first stop (t/T)lines are mean running velocity ± s.d. (dotted lines). (D)Same data as in B but plotted against relative time until first stop(t/T).

We performed such trials on 14 crabs, of which ten were `slippers' and four`non-slippers'. We also performed four controls in which foraging crabs were scared home with no patch. The mean starting distance from home was 26.4±4.3 cm for the slippers, 25.7±1.5 cm for the non-slippers,and 16.9±5.4 cm for the controls. Data are plotted as running velocity relative to home (i.e. closing speed) against proportion of distance home(d/D, gdje d is the distance home from any point in the digitized path, and D is the starting distance from home, Fig. 9A). This plot, which emphasizes the position where the crabs stopped in relation to home,illustrates two features of their behavior on the slippery patch. First, crabs that were qualitatively observed to slip (red lines) stopped briefly before they reached home i.e. their running velocity dropped to zero before reaching home. On the other hand, crabs that ran over a patch but were not observed to slip (blue lines) and crabs that were frightened home with no patch (black lines) ran straight home without stopping. Second, crabs that slipped generally had lower running velocities while they were on the patch (on-patch intervals are indicated by solid line segments) than either non-slippers or controls at a similar stage of the run home. Thus, those crabs with depressed running velocities while on the patch stopped short of home. These results are consistent with the hypothesis that, on returning home, fiddler crabs `play out' a home vector, and stop when that vector is exhausted. Indeed, some crabs even stopped within 2 cm of home, a distance from which they probably could see the burrow entrance. Such crabs ran the short distance home immediately after stopping (within 500 ms), presumably because they located home visually. Thus, while undisturbed short-range (within about 5–6 cm) homing, as in foraging, is aided by visual contact with the goal(Zeil, 1998), rapid homing, as during escape, can result in a short delay between using the home vector system and the visual system to find home. This implies that the visual mechanism does not function during rapid escape until the home vector is exhausted, as in bees (Wehner et al.,1990) and ants (Wehner et al.,1996 but see Zeil,1998). These results also suggest that the distance home is not measured using optic flow or vestibular information. If it had been, crabs that slipped should have continued running until they had measured out the correct distance home, regardless of the time or number of steps taken, time spent running at any particular velocity, etc.

Fig. 9B shows the mean running velocity for slippers (red line) and controls (black line), the latter being the combined non-slippers and controls. We combine these because they are not significantly different (see Fig. 9C) and so can both be used as controls, and we will refer to the combined non-slipper and control paths as controls from this point forward. An obvious question to ask is whether the distance by which the crabs fell short of home was related to the amount of slippage.

This hypothesis rests on the assumption that crabs ran with the same effort on the patch as they did off it i.e. the controls represent what the slippers would have done with no patch, and therefore the home vector will be realized among slippers in terms of time spent running. Alternatively, if crabs measured the home vector by counting the number of steps, the hypothesis assumes the same step frequency in slippers and controls, and so time spent running is still the relevant integration parameter.

To support this assumption we can report subjectively that the slippers were never observed to stop running while on the patch, and so there is no reason to believe their effort was less than that of the controls, which also did not stop until reaching home. A quantitative comparison of the controls to the non-slippers (Fig. 9C) also supports this assumption. As mentioned above, the controls (black line) and non-slippers (blue line) were similar to each other over their entire length,which shows that the patch itself does not cause crabs to reduce running effort. This similarity in velocities is also interesting because the mean path lengths of the controls and non-slippers were quite different (16.8 and 25.7 cm, respectively). Thus, within the range of path lengths we recorded,the shape of the escape velocity profile over relative distance is quite consistent. This means that it may reasonably be used as an estimate –when scaled to the correct length of time – of what slipper paths of various lengths would have been without the slipping.

Estimation of length of home vector from time spent running by slipping crabs. (A) Observed running distance Dobs (open circles)and estimate of home vector length Dest (filled circles)plotted against starting distance D, which is assumed to be equal to true home vector length. (B) Relative error in estimate of home vector length(Dest/D) plotted against observed running time. Lines of best fit, calculated by the method of least squares. See text for details.

Estimation of length of home vector from time spent running by slipping crabs. (A) Observed running distance Dobs (open circles)and estimate of home vector length Dest (filled circles)plotted against starting distance D, which is assumed to be equal to true home vector length. (B) Relative error in estimate of home vector length(Dest/D) plotted against observed running time. Lines of best fit, calculated by the method of least squares. See text for details.

It is clear that our estimate is inaccurate, and overestimates the length of the home vector by as much as 400%. The estimate error, defined as the ratio of the estimated home vector length to starting distance(Dest/D), does not depend on Dobs(F=0.21, P=0.66) or on D, as indicated by the lack of significance in the regression above.

Why would the slipping crabs run for longer than they needed to? A possible explanation is that they continued running because they failed to sense some cue indicating arrival at home. However, they eventually stopped, presumably despite not sensing this cue since they did not reach home. One could similarly argue that fiddler crabs have the flexibility to run the length of their home vector plus or minus a fudge-factor in the event that they reached home sooner or later than expected, to account for possible navigation errors. However, our slipping crabs ran for as little as 96% or as much as 400% of the correct running time (the mean was 172%), which is hardly a reasonable fudge-factor, and all of them stopped without having sensed their arrival at home.

We believe the best explanations for our estimation error are as follows. Either slipping crabs have feedback about their slippage but still, for some reason, stop short of home or slipping steps provide less input to their putative proprioceptive measurement mechanism, thus requiring more steps to cancel the neural correlate of the home vector. Support for both of these possible explanations comes from work on other crustaceans. Crayfish walking over a slippery patch showed altered motor output patterns during steps when the legs slipped, a clear indication that slips are detected by proprioceptors and lead to compensatory reflexes (Barnes,1977). Equally, force-sensitive mechanoreceptors such as the cuticular stress detectors and funnel canal organs measure ground reaction forces generated during stepping, forces that would undoubtedly be lower during steps when the leg slipped(Klärner and Barnes,1986 Libersat et al.,1987). Clearly, more data are needed to understand this result,but a mechanism involving force-sensitive mechanoreceptors is particularly attractive because it could provide a good measure of `effort over time'. Certainly, the use of visual and/or vestibular information seems to be the sensory mechanism that is least consistent with these results.


Uvod

Initial stages of parasitism in insects

Insects and arachnids of medical and veterinary concern (e.g., mosquitoes, sand flies, stable flies, black flies, and ticks) have been studied extensively over the centuries, primarily because of the effect of their parasitic feeding habits on many species of domestic and wild animals, and humans. Indeed, these arthropods affect the health, welfare and production of animals through the transmission of disease-causing pathogens or just through biting them, therefore causing blood loss, allergic reactions, and/or nuisance and disturbance [1]. Evolution of arthropods, from a free to a parasitic lifestyle, took eons under the pressure of a wide range of ecological and environmental drivers, resulting in varying degrees of interactions with their hosts, e.g. from virtually necrophagous larvae, occasionally also causing facultative myiasis, to obligate parasitism. However, scientific information on the insect taxa that evolved only partial parasitic interactions with their hosts, is scant [2],[3], and it puts them in a group of organisms of an as yet undefined parasitic status. For example, most Drosophilidae are known to be adapted to feeding on substrates rich in bacteria, yeasts and other fungi (e.g., decaying or fermenting fruit) [3]. However, some of them display a different feeding behaviour as they may feed on animal tissues or secretions (hereinafter referred as to “zoophagy”), therefore being of medical and veterinary importance. This particular behaviour may represent an evolving step towards parasitism. Indeed, there is still paucity of information on the natural history of these drosophilids, and great part of knowledge available to date derives from incidental findings from studies from the 19 th century [3]. The still limited entomological data on these insects is partly due to the difficulties in breeding these species under laboratory conditions [4]. Here we review the scientific information available and provide an opinion about the main drivers, which might have affected some drosophilid genera of the subfamily Steganinae towards parasitic behaviour.


Relationship to other arthropods

Other terrestrial arthropods, such as centipedes, millipedes, scorpions and spiders, are sometimes confused with insects due to the fact that both have similar body plans, sharing (as do all arthropods) a jointed exoskeleton. However these do not have the important feature of having six legs.

Within the subphylum Hexapoda, a few groups such as springtails (Collembola), are often treated as insects however some authors treat them as distinct from the insects in having a different evolutionary origin. This may also be that case for the rest of the members of the Entognatha Protura and Diplura.

The true insects, those of the Class Insecta, are distinguished from all other arthropods in part by having ectognathous, or exposed, mouthparts and eleven (11) abdominal segments. The true insects are therefore sometimes also referred to as the Ectognatha. Many insect groups are winged as adults. The exopterygote part of the Neoptera are sometimes divided into Orthopteroida (cerci present) and Hemipteroida (cerci absent), also called lower and higher Exopterygota.


Outdoor Hour Challenge: Insects and September Newsletter Edition

So how has your month gone with the Outdoor Hour Challenge focus on insects using the newsletter and weekly ideas? Our family has enjoyed the easy way we can incorporate nature study into a very busy high school week. I love having a month long focus.

Would you like an example of how one family used the Insect Study Grid, the Insect Study notebook page, and the small square study this month? Get ready to see how simple it was and how successful they were in their efforts!
Sarah from Granwood Explorers shares their entry: Outdoor Hour-Focusing on Insects. What an excellent month they had and what a great example for the rest of us!

Get ready for one fully loaded blog carnival! What a great month of nature study from all over the world!

Andrea at the Loopy Homeschooler shares their ant study with the carnival. They were actually able to identify their ants and her daughter created an awesome nature journal entry using the Insect Study notebook page from the ant challenge. Read all about it: Outdoor Hour Challenge #3 .

Leah from The Making of a Mom has joined the OHC carnival for the very first time! She submits this entry: Nature Study Co-Op September (Ants) for us all to read. What a lot of happy faces and so many interesting discoveries! I really enjoyed reading about their co-op and so will you.

Insect Study Grid

Shirley Ann from Under An English Sky submits their Insect Grid Study. She says, “My youngest has decided that she prefers the notebooking pages to keeping a journal, so she used her grid as a notebooking page, adding some finds to the back of the page.” It is wonderful to see families adapting the OHC to fit their style of learning. You don’t want to miss her awesome images of colored insects in this post as well.

Tricia from Hodgepodge shares How Summer Nature Study Complements High School Biology . What a wonderful entry for the carnival! Tricia shows how they have been looking for insects and pulling in their high school biology work to make a wonderful mix of fun and learning.

Bugs, Insects, Butterflies, and Creepy Crawlies-Oh My! from Cristy at Crafty Cristy documents their insect study so far using the Insect Grid Study and Insect List found in the newsletter. I learned a few things about cicadas in her entry and they are definitely learning a lot this month about insects. They have also shared their September Insect List for you to view along with images.

Rachel’s American Grasshopper

Rachel from All Things Bright and Beautiful has put together their month long study of insects into a gorgeous entry with images you will want your kids to see: Buggy Bugs . Which image is your favorite?

Fall Insect Walk! Angie from Petra School has submitted this wonderful example of a fall insect walk with her boys. I always appreciate their casual in-their-own-backyard nature study time and Angie’s images really tell the story. Angie and her boys would like to also share their Queen Anne’s Lace entry with carnival readers. They were able to incorporate some insect observations along with their QAL time…don’t miss the grasshopper image in their entry!

Outdoor Hour Challenge #22 is where Catherine from Grace to Abide decided to start their insect study. They were able to identify a few of their butterfly finds from a local park and then they visited a butterfly garden. I agree with her…butterfly gardens are magical!

Virginia from Livin’ Lovin’ and Learnin’ shares their entry The Grid-Sept 2012 Insects showing how their family of children of all ages has enjoyed this month’s focus. Another magnificent grasshopper photo in this entry! They also completed a study of a specific insect, the Illia Underwing Moth . What a beautiful creation to observe up close. One last entry from this family…. Golden Ponds Nature Walk . They found many interesting and seasonal subjects to enjoy and share with all of you. Thanks for a glimpse into your nature study this month.

Carol’s really big stick insect sitting on a camellia bush: Journey and Destination.

Carol shares their September Nature Notebook entry with the carnival this time around. They live in Australia where it is spring and everything is coming alive. Check out their really big stick insect! She also shares some wonderful images of other creatures they have observed this month including a Eastern water dragon!

Jenny Anne from Royal Little Lambs shares their Creepy Crawlies entry with the carnival. It must be the season for grasshoppers!

Heidi from Home Schoolroom has written up their Focusing on Insects and Spiders entry for you to enjoy. They incorporated the ideas from the newsletter and OHC Challenge #4 – Finding a Focus to continue a month long study of insects and spiders. Savršeno!

Nadene from Practical Pages has submitted a round-up of their September insect studies using the newsletter and challenge ideas: Nature Study and OHC September. You are in for a treat because she shares their very well done nature journals to inspire you and your children.

Lauren from Serving From Home has written up their monthly nature study entry: Our September Nature Studies-Insects and Apples . They have done a great job this month with their observations, outdoor time, and nature journals. What an encouraging entry!

Nicole from Journey to Excellence shares their month of nature study. You are welcome to read their Small Square Study i njihove Insect Grid iskustva. She also found a pretty white plant that she thought was Queen Anne’s Lace but it turned out not to be: Queen Anne’s Lace . She would appreciate some help in identifying her mystery plant.

Sara from Garner Goings On shares their entry Saying Goodbye to Swallowtails and Cicadas for carnival readers. Check out her beautiful images and the final video of a swallowtail emerging from its chrysalis.

Potpourri
Carey Jane Clark who blogs at enCouragement joins the carnival this month with her entry: Our Nature Study Backpack . She shares how they are using the newsletter study grid and a well prepared backpack to aid their nature study in China.

Michelle from Following the Footprints submits their very first two Outdoor Hour Challenges: Challenge #1 i Challenge #2 . I think this quote from one of her entries sums her experience up well, “I felt so empowered by my success in identifying two plants that it changed the way I looked at nature for the rest of the week. All of a sudden, I was looking at trees in parking lots and across the street wondering what those trees were. I saw a beautiful brown and black bird in my backyard and I wondered what that was. And I am so excited to find out! Such a change in me in so little time!”

Kim from A Child’s Garden shares their unexpected nature study: Puffballs! She does a great job of explaining what they are and her images are interesting too.

Michelle has also submitted their Outdoor Hour Challenge #3 for you to read. They are humming right along with their family nature study, and this time it is in their very own backyard! One last entry from this enthusiastic family: Outdoor Hour Challenge #4 . So many things to like about this entry and I think they accomplished Challenge #4 very well with their feather collections in the nature journals.

Ann from Harvest Moon By Hand has put together their Hummingbirds-Outdoor Hour Challenge entry for you to enjoy. Take a look at their Minnesota hummingbird study and be inspired! They were also able to complete their Red Birds Challenge from the Handbook of Nature Study. Ann says, “It was as if the birds that had red on them knew we were learning about them today. Such an inspiring and uplifting afternoon!” What a treat!

Makita from Academia Celestia shares their Exploring the Redwoods study with the carnival. They were able to observe two different groves of redwoods here in California and follow up with additional reading and journals. They also had some unexpected insect study: Looking for Birds, We Discovered Caterpillars . Read their Water Quality Monitoring entry to learn more about their participation in worthwhile citizen science projects.


Don’t forget to share your blog entries with the Outdoor Hour Challenge Blog Carnival. All entries done in October are eligible for the next edition. The deadline for entries is 10/30/12 and you can send them directly to me: [email protected] or submit them at the blog carnival site (link on the sidebar of my blog).


Insect endosymbionts: manipulators of insect herbivore trophic interactions?

Throughout their evolutionary history, insects have formed multiple relationships with bacteria. Although many of these bacteria are pathogenic, with deleterious effects on the fitness of infected insects, there are also numerous examples of symbiotic bacteria that are harmless or even beneficial to their insect host. Symbiotic bacteria that form obligate or facultative associations with insects and that are located intracellularly in the host insect are known as endosymbionts. Endosymbiosis can be a strong driving force for evolution when the acquisition and maintenance of a microorganism by the insect host results in the formation of novel structures or changes in physiology and metabolism. The complex evolutionary dynamics of vertically transmitted symbiotic bacteria have led to distinctive symbiont genome characteristics that have profound effects on the phenotype of the host insect. Symbiotic bacteria are key players in insect–plant interactions influencing many aspects of insect ecology and playing a key role in shaping the diversification of many insect groups. In this review, we discuss the role of endosymbionts in manipulating insect herbivore trophic interactions focussing on their impact on plant utilisation patterns and parasitoid biology.

Ovo je pregled sadržaja pretplate, pristup preko vaše institucije.


In grasshopper metamorphosis, you can see that young grasshoppers (1-5) look very similar to the adults (6) as they grow larger.

Insects that go through three stages of change in their life cycle have an incomplete metamorphosis while complete metamorphosis has four stages.

The first stage of incomplete metamorphosis is the jaje. During this time, the insect will hatch into a form called a nymph.

The nymph is basically a small version of the adult insect. This is very similar to how a child looks like his or her parents. Nymphs usually have a thin exoskeleton and no wings. They eat the same food as their parents and live in the same place. As insect nymphs grow larger, their exoskeleton becomes too tight and they must replace it.

Once a nymph outgrows its exoskeleton it will go through a process called molting, in which it leaves the old “skin” or exoskeleton behind. The new “skin” will harden and become the new exoskeleton. This will happen many times until the insect finally becomes the size of an odrasla osoba.

Insects that have an incomplete metamorphosis life cycle include true bugs, grasshoppers, cockroaches, termites, praying mantises, crickets, and lice.

These two lubber grasshoppers are examples of a nymph and adult form. Can you tell which one is the nymph and which is the adult? Images by Bob Peterson and Fredlyfish4 via Wikimedia Commons.


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