ioo INSECTS 



centage of the triungulins never get beyond that stage; 

 but when there has been an abundance of hoppers and 

 egg-pods are numerous, matters are easier for the 

 enemy and a larger percentage secures food. In this 

 way it happens that after a season of grasshopper 

 abundance a season of blister beetle abundance is al- 

 most certain to follow, and any abnormal increase of 

 the former is almost sure to be checked by the cor- 

 responding increase of the latter. 



A very material change is introduced by the migrat- 

 ing habit of some of the host species. Blister beetles 

 are not great travellers, while a grasshopper swarm 

 may fly for hundreds of miles, clear out of the faunal 

 range of their check. But in such instances, while 

 they may have a year or two of unusual freedom for 

 development, they become in time victims of the un- 

 favorable climatic conditions in their new surroundings 

 and are crowded back into their natural domains, under 

 the control of their normal enemies. 



While, in a way, it is correct to refer to these beetles 

 as parasitic, they are not really more so than the Man- 

 tispids that feed in spider egg-sacs, and in the case of 

 those feeding in the cells of bees they are even less so. 

 For here the egg or young larva of the bee is only eaten 

 to remove the owner of the stored food and the real 

 object of the "parasite" is the stored provender. It 

 is therefore a robber rather than a parasite, unless we 

 use the latter term in a very broad sense. 



As to predatory forms, the order Coleoptera con- 

 tains a great number. All those species that have 

 filiform or thread-like antennae, comprising the fami- 

 lies Cicindelidce (tiger-beetles), and Car abides (ground 

 beetles), Haliplidce (diving beetles), and Dytiscidce 

 (water tigers), are predominatingly feeders upon other 

 insects. A few feed on vegetable tissues as well or as 



