Cannibalism in baby spiders

Wow, combine the word “spider” with “cannibalism” in the title of an article and there’s no way I can’t read it!
The specific title of the article I found is, “Cannibalism in spiderlings is not only about starvation.” 

Baby spiders eating each other? What?!

Turns out that after spiders hatch, they tend to congregate for a while in a big group. This is called gregariousness. The baby spiders seem to get a long for a while, but then at some point they start acting aggressive…even eating each other!

The study I read tried to figure out if baby spiders sometimes eat each other simply because they are hungry, or whether they do it for some other reason(s).

The species they studied was Angelena labyrinthica. (What a poetic name!) They put recently-hatched babies in groups and varied the amount of food (dead flies) they were given. Basically they found that the group that received no food, and would therefore be starving, did NOT cannibalize each other. Cannibalism seemed to be linked to spiders that had moulted (shed their skin). The authors suggest that when moulting occurs, some changes in communication between the spiders happen and it often leads to aggression. (I have visions of Dr. Bruce Banner changing into The Hulk…)

So it appears that cannibalism between spiders, and aggression in general, is more complicated than just being hungry. Spiders communicate things to each other that we are just beginning to find out. Such complexity in such a tiny species really makes me appreciate the whole animal kingdom that much more. Awe is more like it. Who knows what happens in little spider worlds?

A note on the name of the spiders: Why are they named labyrinthica? These spiders apparently spin flat, horizontal webs that are attached to funnel-like “retreat webs” that are like a maze or labyrinth. 

Imagine all the cognitive calculations involved in spinning a contraption like that, then navigating within it! Very impressive for a tiny being.

References

     Lessen, P., Trabalon, M., & Jeanson, R. (2016). Cannibalism in spiderlings is not only about starvation. Behavioural Ecology & Sociobiology, 70, 1669-1678.

     Wikipedia. Angelena labyrinthica. Retrieved September 25, 2016 from: https://en.m.wikipedia.org/wiki/Agelena_labyrinthica#

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