THE INSECT AS A PARENT 271 



themselves as to kill and eat the proper occupant of the 

 nursery after robbing it of its food. 



None of the true digger-wasps are guilty of this 

 underhand behaviour ; but the dainty little ruby wasps 

 (Chrysididce) are " cuckoos" one and all, in the sense that 

 they lay their eggs in the nests of other Hymenoptera. 

 In most cases, however, it is believed that the alien larva 

 does not eat the stored food, but waits patiently until the 

 wasp larva has finished feeding, and then devours it. 

 Indeed, the parental activities of insects range from honest 

 labour of the most toilsome kind, through every con- 

 ceivable grade of shiftlessness and trickery, to the grossest 

 parasitism. Moreover, these varied conditions are often 

 intermingled in a manner which well-nigh baffles descrip- 

 tion. Some of the gall- wasps, for example, have an 

 extraordinary number of dependents. These may be 

 roughly divided into three groups. First, inquilines — 

 species which do not themselves make galls, but lay their 

 eggs in galls already formed ; their larvae feed upon the 

 substance of the gall, but often, though not invariably, kill 

 the offspring of the actual maker by pressure. Secondly, 

 true parasites, which thrust their ovipositors into the gall 

 and lay their eggs in or near to the bodies of the rightful 

 tenants — or it may be the bodies of the inquilines. Thirdly, 

 commensals — messmates as it were — which feed upon the 

 tissues of the gall without encroaching upon the rights of 

 the inmates. From a mass of oak-apples, the late Mr. 

 Francis Walker reared seventy-five species of insects, 

 representing seven orders, not to mention a few spiders 

 and mites. In all there were upwards of 55,000 indi- 

 viduals ! Needless to say, the precise status of many of 

 these hangers-on remains obscure ; but we may take it 

 that they are all beholden, either directly or indirectly, to 

 the original gall-maker. 



