Lasia klettii: Fotos af April Nobile, SAG
For det meste er fluer ikke et insekt, jeg bliver alt for begejstret for. Men, den gådefulde familie Acroceridae er undtagelsen. Jeg vil begynde at dele nogle interessante slægter fra tid til anden – familiens morfologi er forbløffende forskelligartet. De fleste af mine dage tilbragte på museet med at inventere vores enorme samling af over 16,000 Acorcerider (alias småhovedede fluer). Det lyder måske ikke alt for imponerende, når du sammenligner det med andre mere rigelige familier (og den blegner i forhold til over 17,500,000 Andet eksemplarer vi har på museet); men det viser sig at repræsentere mange, hvis ikke de fleste, af alle kendte eksemplarer for hele familien. Mens der sandsynligvis er store samlinger af disse fluer i andre institutioner, California Academy of Sciences kan nemt gøre krav på rekorden lige siden modtagelsen af samlingen af Dr. Evert I. rulle (som af og til kommer ind for at arbejde fra museet).
Acrocerider viser sig at være en ret svær gruppe at studere på grund af hvor sjældne de er i naturen, deres parasitoidbiologi, og hvor svære de kan være at fange på vingen. Deres store thorax er spækket med muskler, der skyder fluen gennem luften – så hvis du ikke fanger dem ved en blomst, længes du efter en malaisefælde. Ev fortalte mig en historie om at lære at fange disse på fløjen i Costa Rica. Du står i modvind fra en kollega i marken – så snart nogen hører noget glide forbi, du svinger vildt i håb om at fange fluen ved et tilfælde… det virker en gang imellem. Disse fluer er også de eneste kendte endoparasitter af voksne edderkopper (der kan være en registrering af en Tachinid…). Ovenstående slægt, NeoLasia, er en parasit af Theraphosid taranteller (noget som Aphonopelma). Som en larve arbejder fluen sig op ad benene på en edderkop og borer sig ned i maven, hvor den så sætter sig ind ved siden af boglungen og prikker et lille åndehul.. Så venter den tålmodigt på, at edderkoppen nærmer sig modenhed. Med hun-taranteller, fluen kunne være i dvale i årtier. Til sidst sker der noget, der ligner filmen Aliens, og larverne lever af edderkoppens indre organer dukker derefter op for at forpuppe sig. Men at finde ud af, om en edderkop har en parasit eller ej, er umuligt uden en dissektion – så store samlinger af levende edderkopper skal vedligeholdes for at opnå værtsposter. Parasitoid biologi er bare så cool.
Ovenstående eksemplar (Lasia klettii en ny, unavngivne, arter) blev samlet ind 1977 af Schlinger nær byen Alamos, Mexico – på blomster med den sandsynlige mimikmodel, en Chrysomelidae bille (bille mennesker, alle ideer ud over familien?).
Very interesting! Out of curiosity, because you mention large collections of live spiders, has any researcher reached out to the hobby tarantula keepers in a quest for specimens? While I have never seen something as spectacular as the above emerge from a wild caught tarantula, I have heard from a few people who ended up with “strange” flies in the past…
Reaching out to them for actual tarantulas has lead to quite a few specimens for Brent Hendrixson on his revision of the genus Aphonopelma, at least for the USA native species. There also are frequently imports of various species brought in from Central and South America, which is not a practice I like or am comfortable with…but it might lead to at least a few specimens given the numbers involved. Just a thought.
I think the answer is somewhat. I’ve reached out on message boards and even recently gave a short talk to the SF Bay Area Tarantula Society. The problem comes down to peoples immediate response when they see a giant grub crawling out of their spider – they reach in and grab their prize specimen and in the process damage the larvae or pupae of the emerging fly. As it turns out these flies are pretty sensitive before pupating and while I’ve seen lots of maggot images, never seen a fly reared by a hobbyist. I think the biggest hurdle is that people only discover what they are after they have had a spider die – and chances are it’ll be years before another one of their wild caught immature spiders are parasitized!
That makes a lot of sense, I guess it didnt really occur to me that for most people having a parasite emerge from one of their captives is a bad thing…that sort of thing would make my day. 🙂
Especially if that spider cost you a few hundred dollars!!
I wonder if that fly sees very well. 🙂
First impression of the beetle is a species of Chrysolina (subfamily Chrysomelinae), but my knowledge of Neotropical chrysos is limited.
Thanks for the genus ballpark – I’ll have to dig through our collections here to see if I can’t narrow it down more.
Did you mean that these acrocerid flies are the only known dipteran endoparasites of adult spiders? There are certainly spider-parasitic nematodes, and mantidfly larvae can crawl into the book lungs of their spider hosts and feed on hemolymph while hitching a ride to the egg deposition site.
http://en.wikipedia.org/wiki/Mantispidae
And here’s a cool post about a mantidfly larva on a spider, preserved in amber!
http://blogs.discovermagazine.com/notrocketscience/2011/03/28/spider-boarding-insect-preserved-in-amber/
(Selvfølgelig, that one’s on the outside of the spider, but the post also has more info on other tactics.)
Thank you for pointing that out! You’re correct of course, when I was thinking “no other endoparasitoids” I totally neglected non-insects such as nematodes. I should have recalled how tricky it can be to control nematode infestations in captive bread spiders!
I also did not know that about mantidflies. Actually I should catch up on the literature, there may be other diptera or hymenoptera parasitoids more recently known. Very cool, thanks for the link.
Augh augh augh and here’s a picture of a huuuuuge nematode coming out of a spider! It’s even one of the behavior-modifying parasites — it induces its host to seek out water before dying, so the nematode can complete its life cycle. (Like the horsehair worm in crickets!)
http://www.abc.net.au/science/k2/stn/spider.htm