INTERRELATION "I 



273 



another lar.^e hymeiiopteron, I'nnK'x tolnmba (Fig. $o). up* 

 larvae tin- larva of .l/o;,//V/v.s 



Tilt 1 enormous family Uraeonida'. closely related to I< hneumonid;r. 

 is illustrated by the common . 1 /></;/ /r/rv roHi^rc^ilns, whit h lay.> its eggs 

 in the caterpillars of \ arioiis Sphiiu'i< la-. The parasitic larva- feed upon 

 the blood and possibly also the fat body of their ho>t, and at 1< 

 emerge and spin their cocoons upon the exterior of the catcrpillar 

 279), sometimes to t lie number of several hundred. Species of Aph itlius 

 transform within the bodies of plant lice, one to each host, and the i.- 

 cuts its way out through a circular opening with a correspondingly 



FIG. 279. A tomato worm, Protoparce sexta, bearing cocoons of the parasitic Apanteles 



congregatus. Natural size. 



circular lid. Chalcididae, of which some four thousand species are 

 known, are usually minute and parasitic; though some are phytopha- 

 gous, for example, species of Harmolita (Isosomd) which live in wild or 

 cultivated grasses, and the clover seed-midge Bruchophagus funebris. 

 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 caterpillar of Plusia. Proctotrypidae are remarkable as parasites. 

 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 Ipng. A large proportion 



18 



