84 



a certain black wasp catches these same caterpillars from the ])alm 

 leaves, stings each one to paralyze it, and stores up half a dozen 

 of them in a cell of its nest in which an egg has already been de- 

 posited, and tlic larva hatching from this egg eats all the cater- 

 pillars in a few days, wc do not call the wasp a parasite ; but 

 speak of it as proving upon catcrijillars. In each case, however, 

 the caterpillar which is the victim is stung and paralyzed so that 

 it remains in a living though inactive condition, until being 

 eaten. In the case of the Braconid parasite, from one to twenty 

 larvae occupy about three to four days in eating one caterpillar ; 

 while in the case of the wasp, its larva eats one or more per day 

 of the paralyzed caterpillars stored in the cell for it. Api^arently 

 if one is a parasite, the other should be considered a parasite also. 

 Neither of these quite answers to the condition of the definition 

 of parasitism with which we started : that the host and parasite 

 are Jk'iiio; together, the latter at the expense of the former. 



Among insects, parasitism is carried on in so manv different 

 ways that a general definition would have to be modified to fit 

 many of the cases. This diversity is partially due to the trans- 

 formations that insects pass through from the ep;;s!; to maturity. 

 Not so with all, but in general, from the es^s^ hatches a larva, 

 which mav be a grub, maggot, caterpillar, etc., which eats and 

 grows until attaining its normal size, then changes to the puna 

 stage, which is a quiescent stage externally, but very active in- 

 ternally, as many changes of structure take place, ressulting in 

 the formation of the adult insect, which emerges from the pupa 

 in due time. 



Now about insects, there are certain families and groups that 

 are always parasites on other insects. Some of them are para- 

 sitic in eggs of other insects ; some are parasitic on the larvae ; 

 others parasitic on the pupae ; and yet others parasitic on adult 

 insects. All. however, resulting in the death of the host, at lea.st 

 in the great majority of cases. All of these are called i-)rimary 

 parasites. Now some of these primary parasites may themselves 

 be attacked by parasites, and these in turn may also be jxirasitizcd. 

 all of which are called secondary or hyperparasitcs. 



Kach parasite has its own method of attacking the host and 

 its own peculiar development ; so much so, that- there are about 

 as many different methods as there are diflferent species of i^ara- 

 sites ; but for the more closely related ones the habits arc often 

 verv similar. 



With all this diversity of habits, it is small wonder that the 

 study of insect parasitism is so fascinating and that entomolo- 

 gists of modern times are giving so nuich attention to it. ATany 

 an entomologist has been content to sit in his study or labor- 

 atory and write descriptions and classify parasites withotit giving 

 the lea.st thought to their habits ; but to most entomologists now- 

 adays the study of the habits of these parasites is of f;ir more 



