INTERRELATIONS OF INSECTS 



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 truncatellum) from a single 



FIG. 272. 



A tomato worm, Phlegethontius sexta, bearing cocoons of the parasitic Apanteles con- 

 gregatus. Natural size. 



caterpillar of Plusia. Proctotrypidae are remarkable as para- 

 sites. Most of them are minute; indeed this family and the 

 coleopterous family Trichopterygidae contain the smallest 

 winged insects known species but one third or one fourth 

 of a millimeter long. A large proportion of the Proctotry- 

 pidae 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. 



