iv] DIPLOPTERA 55 



mauls, a fly which very closely mimics wasps in its 

 colour pattern, moving over the combs and apparently 

 devouring the larval excreta at the tops of the cells, 

 in fact acting scavenger from door to door. Many 

 species of both insects and of other small animals 

 have from time to time been found in wasps' nests. 

 Some are undoubtedly parasites, others thieves, others 

 mere chance sojourners glad of a warm and dry 

 shelter. Two of the parasites deserve further notice. 

 A thread- worm was found by Kristof projecting from 

 the body of a drone wasp; I myself have on several 

 occasions made a similar observation: the fact that 

 this parasite occurs, so far as we know, only in the 

 drones raises a suspicion that some peculiar form of 

 food is supplied to the drone grubs, but we have no 

 evidence bearing on this question. The other is a 

 remarkable beetle (Rhipiphorus paradoxus). The 

 larva of this beetle is believed to leap upon the 

 bodies of worker-wasps when they are gathering 

 wood-fibre oft* the surface of timber. It is thus 

 carried by the returning insects into their nest. It 

 now eats its way into a wasp-grub and devours the 

 less important tissues of its host: when it becomes 

 of such a size as to threaten the life of its unfortunate 

 victim, it passes out through the skin of the wasp- 

 grub, plugging the wound with the skin which it itself 

 moults as it issues, and now becomes an external 

 parasite upon the same host. It refrains from killing 



