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MOTHERS have to put up with many things from their children, but being eaten
isn’t usually part of the deal. Young Japanese foliage spiders,
Chiracanthium japonicum, indulge in this seemingly ungrateful
tactic. After spending a couple of weeks cooped up in a folded leaf, the hundred
or so spiderlings tuck into Mum before leaving the nest. Masatoshi Toyama at
Hokkaido University has worked out the reason for her sacrifice. When he denied
some spiderlings their parting meal (Journal of Ethology, vol 19, p 69)
they failed to triple their weight in a day like the others. Crucially, this
feast allows them to move into the next developmental stage, when they grow long
legs adapted for dispersal.