- Joined
- Jun 22, 2004
- Messages
- 972
I came across this one yesterday when I stopped to look at a curious web in the dead end-branches of a willow tree. It was about 6 feet off the ground and I saw a tangled web, about 5 inches diameter, with a brown spider in the center. I'm thinking, "Theridiidae of some kind."
A closer look revealed a spider with a parasitic larva on its abdomen! I believe now that the spider was an araneid, and the tangled web was the result of chemical "instructions" it received from the larva. My understanding is that after the spider is initially parasitized, it goes through it's normal life cycle of building orb webs, trapping food, etc. Then, when the larve reaches a certain size, or age, or point in its development it injects a chemical into the spider which causes the spider to spin this uncharacteristic web - which, in reality, is a protective web in which the larva can finish consuming the spider and safely pupate.
Anyway, I took some pictures, but in my excitment I forgot to take whole-web pictures (Arrgghhh!). I did get a closeup of the pair in the web, which includes some interesting star-like patterns of threads (see later picture).
I collected them and took some more pics under the scope. It's a good thing I did, because just a couple of hours later the larva finished eating the spider's abdomen and started to pupate. It completed its pupation during the night. I have it in a covered petri dish and will take pictures of whatever energes.
I believe I came upon the spider/parasite pair shortly after the spider finished building its "death web," since the larva didn't take long after that to finish eating it.
So, here are some pictures of this interesting event:
Spider and parasite in the "death web":
Part of the death web, showing cluster of threads within the web, radiating from a central point:
Head of larva at top:
A couple of hours later. Not much left of the spider's abdomen:
The pupa is about 5 mm long:
A closer look revealed a spider with a parasitic larva on its abdomen! I believe now that the spider was an araneid, and the tangled web was the result of chemical "instructions" it received from the larva. My understanding is that after the spider is initially parasitized, it goes through it's normal life cycle of building orb webs, trapping food, etc. Then, when the larve reaches a certain size, or age, or point in its development it injects a chemical into the spider which causes the spider to spin this uncharacteristic web - which, in reality, is a protective web in which the larva can finish consuming the spider and safely pupate.
Anyway, I took some pictures, but in my excitment I forgot to take whole-web pictures (Arrgghhh!). I did get a closeup of the pair in the web, which includes some interesting star-like patterns of threads (see later picture).
I collected them and took some more pics under the scope. It's a good thing I did, because just a couple of hours later the larva finished eating the spider's abdomen and started to pupate. It completed its pupation during the night. I have it in a covered petri dish and will take pictures of whatever energes.
I believe I came upon the spider/parasite pair shortly after the spider finished building its "death web," since the larva didn't take long after that to finish eating it.
So, here are some pictures of this interesting event:
Spider and parasite in the "death web":
Part of the death web, showing cluster of threads within the web, radiating from a central point:
Head of larva at top:
A couple of hours later. Not much left of the spider's abdomen:
The pupa is about 5 mm long: