Spider With Unidentified Passenger

[crotermund]

I've seen plenty of signs of parasitic wasps on caterpillars & stuff like that, but this seems a bit odd to me. I am curious how this particular connection was established. Any ideas? Anybody know what this is?

[rjlittlefield]

Very interesting!

Some time ago, I posted pictures of a somewhat similar beast on a Spruce Budworm Caterpillar. Mine was tentatively identified as an ectoparasitoid wasp larva, nothing more definite. Yours does not have a distinct head capsule. To my rather untrained eye, it looks more like a fly larva. But I don't know any more than that. I'll be interested to hear what other info comes in!

--Rik

[crotermund]

Rik -
I have to admit, my first impression was also some type of fly larva. It does have a maggot like appearance to it. For some reason it seems a bit peculiar to me, though, for a fly larva to be crawling around on the body of a living spider. I'm sure there is a logical explanation, though, and am also anxious to hear what others might have to share.

Nice series of pics, btw, and an interesting post. Your "beast" appears to be a bit smaller, but i'm really not quite sure.

[Ken Ramos]

An unusual image, the spider is or appears to be at rest and quite possibly does not care that the larva is there. However there could be a mutualistic releationship between the two. Could it be that the larva provides a service to the spider by removing small harmful parasites from the spiders abdomen and the larva in turn gets the nourishment it requires plus the added benifit of not being turned upon by the spider, at least maybe until it tries to leave the spider. Sort of like the "black widow" thing, the male has to leave the female in a certain way or she turns on him after mating. What ever the case maybe, a very good and unsual image

[rjlittlefield]

Your "beast" appears to be a bit smaller, but i'm really not quite sure.

Me either. It's hard to record scale in the field, but those last two of mine were shot on tabletop at home. I did shoot a ruler at the same time, and I have no idea why I did not use it to put a scale bar in the pictures.

Anyway, what it shows is that the wasp (?) larva was 2.0 mm long as pictured. It grew to about twice that long before both the caterpillar and the parasite died.

--Rik

[beetleman]

A wonderful and strange photo Craig. That is one big larvae--maggot he is supporting. Usually the Parasite lays its egg on the host and the larvae burrows into the host and eats it from the inside out. Being this is so large makes it rather strange. It does not look like it ate the spider unless the spider is dead. It could be some kind of “hitching a ride” type of parasite that eats the spider from the outside???? This link shows a big grub like thing on a spider!!!! http://www.amonline.net.au/factSheets/h ... piders.htm

[Gordon C. Snelling]

That image on the link pretty much for me, locks it up.

[crotermund]

Thanks a lot for the input everyone. Doug, as Gordon mentioned, that image you included seems to be the exact type of situation we have here also. I always thought the larvae burrowed and ate the host from the inside out as well. Nature never fails to surprise us, though.

[Gordon C. Snelling]

Typically they do indeed eat from the inside. I suspect what is happening here is that fully mature parasite has emerged from the nearly dead spider and is seeking a place to pupate.