THEIR RELATION TO EACH OTHER 115 



surface by a little capsule which serves to hold the 

 active young larva that hatches almost as soon as the 

 egg is laid. Sooner or later the feeding caterpillar ' 

 comes within range of this waiting maggot and then 

 with a dart the parasite hooks into the skin of its host, 

 is torn from the capsule attached to the leaf and bores 

 its way in. It will be readily appreciated that this 

 plan of scattering the numerous minute eggs over the 

 foliage on which caterpillars are feeding is likely to 

 reach the hosts in proportion to their abundance. 

 If, for instance, a brood of gypsies completely strips 

 a tree, every Tachinid egg on it will also get into the 

 caterpillar stomachs to the undoing of a vast percentage 

 of them. It seems like a hap-hazard way of doing 

 things and, no doubt, when caterpillars are scarce, 

 very few of the thousands of Tachinid eggs ever find 

 their way into any appropriate host. 



It is in the order Hymenoptera, including the bees, 

 wasps, ants and the like, that we find the most inter- 

 esting specializations in the way of predaceous and 

 parasitic habits; specializations so numerous and 

 interesting that they demand volumes for their proper 

 presentation and can be only referred to here. 



First of all, there is that enormous series of solitary 

 wasps, including the mud- wasps, digger-wasps, wood- 

 wasps and whatever other modifications of the term 

 may be employed; all of which make cells of some 

 kind cither in the ground, in pithy stalks, against an 

 angle, in a crevice or even attached to a twig, and these 

 cells are stored with food enough to bring the larva to 

 maturity. Most of the wasp larvae are helpless, foot- 

 less creatures, absolutely incapable of seeking their 

 own food, and they depend altogether upon the store 

 that has been gathered by the parent, and that store 

 consists largely of insects or spiders, which are par- 



