Spider Sunday: Silver stretch spider

Another sunday, another spider. This time the silver stretch spider (Tetragnatha montana). These past weeks I’ve seen quite a number of them in the garden. They mostly lay stretched out (hence the name) in the middle of their web or on a leaf in the vicinity. Members of the genus Tetragnatha have relatively long jaws and together with the palps, it looks like they have 4 jaws (tetra means 4; gnatha means jaw). The jaws are visible in the pictures below even though I did not zoom in on them.

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Unlike other spiders, male stretch spiders don’t have to woo a female with dance or gifts. They do need to be careful not to be eaten during mating, so they lock the females jaws in their own jaws to make sure that she can’t eat him. There are a couple of great videos on stretch spider mating on YouTube, I encourage you to check those out if interested!

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As with almost every other living creature, the silver stretch spider risks parasitic infections. One such parasite is a parasitic wasp, Acrodactyla quadrisculpta. It lays an egg on the back of a living spider. The larvae grows and feeds itself by making tiny holes in the spider to suck out bodily fluids. When the larvae is almost ready to mature, it lets the spider built a web that is atypical for the spider, but beneficial for the parasite to use as a cocoon to further develop in. The spider dies and its remaining fluids are sucked out by the larvae (a phenomenon called the big slurp). The larvae discards the empty spider remains and subsequently pupates as a mature wasp. See video clip below (warning: this video could serve as inspiration for horror movies!).

Source of clip: Modification of Tetragnatha montana (Araneae, Tetragnathidae) web architecture induced by larva of the parasitoid Acrodactyla quadrisculpta (Hymenoptera, Ichneumonidae, Polysphincta genus-group). Korenko et al. (2015).

Extra info:

Dutch article

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