BEES, WASPS, ANTS, ETC. 



511 



The female Chalcid lays her eggs either in oi' upon some other insect in one of its 

 early stages of growth. The larvas usually feed internally, but occasionally they feed 

 externally upon other larvse. All of the species of the sub-family TrichogramminiB, 

 so far as we are aware, are parasitic upon the eggs of species of other groups, usually 

 of Lepidoptera and Coleoptera. All other chalcids (with the exception of certain 

 species of Eiipdmus whicli are parasitic upon the eggs of Orthoptera and Heteroptera, 

 and occasionally of Lepidoptera) oviposit upon larviB, and issue eithej- from the larva 

 or pupa. In the case of the internal feeders the larva transforms to a naked pupa 

 within the body of its host, while the external feeders often spin a slight cocoon. 

 With some of the Eulophinas, however, the host is entirely destroyed, and the larvae 

 transfomi without covering upon the surface of the leaf. In this case, however, the 

 pupal epidermis is very thick and tough, so much so as to obscure the form of the 

 insect. 



Not all of the ChalcididsB are parasitic. The sub-family EurytominsB closely 

 approaches tlie Cynipidse, not only in structure, but also in habits. The genus Tsosoma 

 of this sub-family contains several species which are phytophagous (/. hordei, I. tritici. 



Fig. 637. — Tomocera califomica, male and female. 



and I. vitis), and one of them (Z hordei) causes an abnormal growth which is very 

 like a gall. The species of the closely allied genus Eurytoma are bred in large num- 

 bers from Cynipid and Cecidomyid galls, and must be considered as inquilinous rather 

 than as parasitic. 



All of the orders of Hexapoda, with the exception of the Thysanura and Derma- 

 toptera, are subject to parasitic attack from members of this family. Fi-om the gigantic 

 larva of Telea polyphemus which supports its hundreds of ravenous larvie of Spilo- 

 chalcis marice, down to the minute pedunculate egg of Hemerobius with still more 

 minute parasitic Trichogramma, hardly a species escapes. The amount of good they 

 accomplish in the destruction of noxious insects is very great, and the sudden cessation 

 in the work of some injurious horde, so often noticed by the agriculturist, is often in 

 great measure due to their good offices. 



The family Peoctoteupid^ is closely related to the preceding both in structure 

 and in habits. The difficulty in separating certain members of the two groups has 

 always been great, for want of some exact and decisive distinguishing character. Such 

 a character has at last been observed by Thomson, and consists in the fact that in the 

 Proctotrupidce the pronotum always extends to the tegula, while in the Chalcididse 

 the borders of the mesoscutum always intervene. The Proctotrupidse have not been 



