FIELD BOOK OF INSECTS. 



Less than .75 in. long; thorax and abdomen entirely 

 black nitida. 



3. Female mostly blackish, with fuscous (smoky) wings; 

 male mostly dark brown, with a dark, median stripe or 

 area on the hind end of the thorax atrata. 



Both sexes mostly pale brown; wings not fuscous; 

 abdomen with yellow, lateral stripes, at least in the female ; 

 male without the dark marking on the end of the thorax. 



nortoni. 



4. Exserted portion of the ovipositor not much longer 

 than the body; front wings not dark brown except in and 

 near the marginal cell greenei. 



Exserted portion of the ovipositor two times, or 

 more, as long as the body; front wings dark brown along 

 the basal vein and elsewhere lunator. 



CYNIPOIDEA 



There are several families in this group, the largest and 

 most interesting being the Cynipidas. They are largely gall- 

 makers; see p. 457 and Amphibolips, Plate LXXXVIII. 

 Some Cynipoidea, such as Ibalia, the largest of our Cyni- 

 poids and parasitic on Megarhyssa, are parasitic; others, 

 although breeding in galls, do not have any part in making 

 them but merely feed on the plant tissue which grew be- 

 cause of the activities of another insect. Some of the 

 Cynipid gall-makers have an interesting alternation of 

 generations: adults of generation A produce a certain 

 kind of gall from which hatches generation B; adults of 

 B differ from those of A and make a different kind of gall 

 but their offspring are A, starting the cycle over again. 

 This matter has not been worked out for the American 

 species. 



CHALCIDOIDEA 



A few, such as Isosoma, the "joint-worms" of grain, 

 are plant feeders. As a rule, they are parasitic, a large 

 number of them being secondary parasites, that is parasitic 

 upon parasitic insects. The fact that, in many instances, 

 an individual gets its entire nourishment from a single 



414 



