Immobility: the key to family harmony?

The lethal fighting of larvae in many parasitoid species is a striking exam ple of sibling rivalry. Theory has suggested that such fighting, and subseq uent solitary development, might he irreversible, but phylogenetic evidence suggests otherwise. New empirical work now shows that the loss of mobility in parasitoid larvae, with the retention of fighting behaviour, is one way to escape the trap of solitary development.