The social spider Anelosimus eximius lives in the jungle of a small South American country. These small arthropods live in colonies numbering from several hundred to several thousand individuals. Together, they weave huge trapping nets with an area of tens of square meters and kill the prey caught in them - and this can no longer only be flies with mosquitoes, but also small birds. A large net is effective precisely because it allows you to catch large prey, which then plays a significant role in the nutrition of the colony. Spiders share their trophies with each other and, due to this, live happily ever after.
Although their way of life resembles ants, termites and other colonial insects, such a rigid division of roles (uterus, soldiers, workers) in the spider "collective" is absent or, in any case, it has not yet been discovered. There, everyone is equal, doing the same thing, multiplying in the same way. If they knew how to vote, it could be called a democracy.
A trapping web woven by social spiders.
There are about three dozen species of social spiders all over the world. Most of them live in rainforests.
The new parasite, whose larvae live on the spiders Anelosimus eximius, was discovered almost by accident. Spider biologist Philip Fernandez-Fournier, who studied spiders, drew attention to the atypical behavior of some individuals that moved away from the colony, built a kind of cocoons from folded leaves and cobwebs, and then froze nearby and died. The scientist collected several cocoons and waited to find out which of them would appear. To his surprise, wasps of a previously unknown species appeared from there.
Spiders Anelosimus eximius on the hunt.
Subsequent observations showed that adult wasps try to lay their eggs directly on the spider. The larva hatching from it takes root in the spider's body and, after a while, takes control of its behavior, forcing the spider to perform unusual actions. Having flown out of the cocoon, an adult wasp tries not to move away from its “native” colony, or, if it is impossible to choose a larger one.
It must be said that relations of hunters and their prey in the animal minre, similar in meaning, are not so rare. Thus, the barnacle sacculina parasitizing on crabs, in addition to the almost complete use of all the nutrients and tissues of the crab for the needs of its growing offspring, forces the crab at the end of its life to even take special measures to facilitate the emergence of larvae from its body. The crab chooses a place with a relatively fast current, climbs higher and begins to sway with its whole body, so that it would be easier for the parasite larvae to start their journey.
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But in the world of arachnids, examples of such complete control over the behavior of the victim have not been encountered before.
For details, see an article published in Ecological Entomology.
Sergey Sysoev