|Zatypota specimen |
mounted on a pin.
There are probably hundreds of species of parasitic wasps. Most of theses belong in the family Ichneumonidae. (In fact, they might all be in this family...but I can't remember, and I don't want to lie to you!) Within this family is a subgrouping that includes wasps that specifically parasitize spiders. Members of this group are known as polysphinctine wasps. The female parasitic wasps use their ovipositors to insert eggs into the bodies of many different types of hosts...caterpillars, cockroaches, and as you will soon learn, spiders. These wasps' eggs usually hatch within the host, using it as a food source, shelter, and in some cases as a vehicle to a more suitable emergence area. Today, we will look specifically at a type of parasitic wasp that infects a spider that lives in the rainforests of Costa Rica.
Anelosimus octavius is a type of spider belonging in the trash-web family, Theridiidae. This family is full of spiders with large abdomens that are carried in a distinctive way by members of this family. I can't describe this very well...it's really something you just have to see to understand. This family is also known as the family of "comb-footed" spiders due to these neat little modifications they have on their back set of legs. Spiders in this family are also sometimes referred to as "cobweb" spiders because their webs take on a haphazard cotton-y appearance rather than the intricate patterns created by orbweavers or the distinctive sheets made by funnel-web spiders and their relatives. Some of the more infamous members of this family include members of the genus Laterodectus...also known as black widows.
|A typical web built by Anelosimus octavius.|
|Central platform of web |
showing top of wasp cocoon.
According to reports of observations of infected spiders, the hosts spend a great deal of time and effort preparing the cocoon webs for their parasites. After tireless efforts, the exhausted spiders crawl back into the central part of the site only to become immobile before being consumed by its parasite. The following day, the parasite would began constructing its own cocoon right on top of the area where it ate its host.
It is interesting to think about how this could have evolved among these two species! However it happened, this is yet another awesome example of behavioral modification due to parasitism. Hooray for making your hosts into zombies!