352 APPLIED ENTOMOLOGY 



and glossy black in color. The extremely long abdomen of this insect 

 which in flight is generally carried partly curled up beneath it, and its odd 

 appearance also when at rest, sometimes cause it to be noticed and the 

 remark made that it must be a dangerous animal. This is not the case, 

 however, as the insect is harmless. It is a parasite on June bug larvae 

 which it evidently seems to hunt for in the ground and it is particularly 

 abundant in sandy localities. The writer has seen over 80 of these 

 insects resting on fences, walls and elsewhere in the course of a single 

 early morning walk in the streets of Nantucket, the distance covered 

 being not over four city blocks. The male (Fig. 3676) which is extremely 

 rare or at least seldom seen, has a short, club-shaped abdomen and is 

 about an inch long. 



A general survey of the habits of the parasitic groups of the Hymenop- 

 tera reveals several diversities of life and habits worthy of being presented 

 together. In the first place all stages of the host may be subject to 

 parasitic attack. The egg seems to be selected in some cases and the 

 pupa or the adult in others: larvae however appear to be particularly 

 liable to be parasitized. Where the egg stage is the one endangered, 

 the parasite may consume its host before the latter can develop to the 

 point where it is ready to hatch, thus preventing any injury whatever 

 if the host be an injurious species. In other cases the host though para- 

 sitized is able to complete its embryonic development, hatch, and feed 

 for a time as a larva before it concedes victory to the parasite feeding 

 within it and dies. In the case of larvae the parasitism may cause the 

 death of the host before it becomes full-grown, or the latter may pupate, 

 but progress no farther. Pupae parasitized are destroyed before becoming 

 adult and adults attacked may or may not be able to live until they 

 reproduce. 



These various relations of parasite and host have a bearing on 

 the effectiveness of the parasite. In the majority of cases it is the 

 next generation which is cut off, most of the injury normally caused 

 by the host concerned being done before the parasite stops it, except 

 in the case of the egg parasites which destroy the host before it hatches. 

 Egg parasites of this kind therefore, are generally regarded as the most 

 beneficial, though the great numbers of the other forms make their work 

 very effective. 



Sometimes one parasite only, feeds upon its host. In other cases 

 there may be many, as with some of the Ichneumonoidea, where in one 

 instance over 1,200 were bred from a single caterpillar. It would seem 

 that the parent parasite is able to calculate the amount of food furnished 

 by a host and deposit only a sufficient number of eggs to correspond with 

 the food supply. The more probable explanation, however, is that 



