FOSSORS 287 



sufficient to feed one grub for the whole period of its 

 growth. Having stocked the burrow, the mother lays 

 an egg, affixing it to one of the living but helpless prey, 

 and having sealed up the burrow for good and all, she 

 goes off to make another. Sometimes this process in- 

 volves very heavy labour, for the inert grasshopper, 

 caterpillar or spider has to be taken to the burrow. 

 Usually it is too heavy to be carried in flight ; some- 

 times it can be carried walking, but often it has to be 

 dragged along the ground. In the latter case the fossor 

 first finds and stings the prey, and then excavates the 

 burrow in a suitable spot in the neighbourhood ; but if 

 she can carry her prey the burrow is excavated first and 

 the prey carried back to it, gripped by the mandibles 

 and carried between the legs. It is wonderful with what 

 accuracy the mother will find her way over sticks, stones, 

 bare patches of sand, or through thick grass, until the 

 burrow is reached ; sometimes she travels backwards 

 with her load ! 



It is an obvious saving of this labour to find the prey 

 first, and then excavate the burrow where it lies. 



Another family, however, the Scoliidae, has economized 

 labour even further. The larvae of these fossors feed 

 upon the subterranean larvae of large Lamellicorn beetles. 

 The mother burrows down to them and merely lays her 

 egg upon them in situ, presumably stinging them first 

 to render them inert, as is the custom in the Fossores. 



Lastly, there are the peculiar Mutillidae, whose wingless 

 females, as they run swiftly over the ground, look like 

 brightly coloured ants. These are mainly parasitic upon 

 other Hymenoptera, and do not burrow, but pierce through 

 the walls of the nest and lay their egg upon the larva 

 inside, just as the typically parasitic " Ichneumon " fly 

 lays its egg upon a caterpillar. Thus one can trace all 

 stages between the somewhat crude method of the 

 Belonogaster wasp down to the labour saving parasitism 



