256 



ENTOMOLOGY 



circular lid. Chalcididse, of which some four thousand species are known, 

 are usually minute and parasitic; though some are phytophagous, for 

 example, Isosoma hordei, which lives in the stems of grasses, especially 

 wheat, rye and barley. Chalcids affect a great variety of insects of one 

 stage or another, such as caterpillars, pupae, cockroach eggs, plant lice 

 and scale insects; while some of them develop in cynipid galls, either 

 upon the larvae of the gall-makers or upon the larvae of inquilines. Giard 

 in France reared more than three thousand chalcids (Copidosoma trun- 

 catellum) from a single caterpillar of Plusia. Proctotrypidse are re- 

 markable as parasites. Most of them are minute; indeed, this family and 

 the coleopterous . family Trichopterygidae contain the smallest winged 



FIG. 276. A tomato worm 



, Phlcgethontius sexta, bearing cocoons of the parasitic A pa n teles 

 congregatiis. Natural size. 



insects known species but one-third or one-fourth of a millimeter long. 

 A large proportion of the Proctotrypidae are parasitic in the eggs of other 

 insects or of spiders, several sometimes developing in the same egg; 

 others affect odonate nymphs and coleopterous or dipterous larvae, 

 while several species have been reared from cecidomyiid and cynipid 

 galls, and many proctotrypids are parasites of other parasitic insects 

 in other words, are hyper parasites. 



Hyperparasitism. Not only are primary parasites frequently 

 attacked by other, or secondary, parasites, but tertiary parasitism is 

 known to occur in a few instances, and there is some reason to believe 

 that even the quaternary type exists among insects, as in the following 

 case. 



