THE IX SECT WORLD. 



387 



the straw during the winter will check injury to a great extent. 

 It is certain that some near alhes of Isosoma and perhaps some 

 other genera of Chalcidids are, at least in part, vegetarians ; 

 but, so far as I am aware, none other has proved in any true 

 sense of the word injurious to cultivated crops. Hence, although, 

 especially in the central and western parts of the United States, 



Fig. 446. 



Isosoma tritici. — a, b, larva ; /, adult female ; g, fore-wing ; A, hind wing ; other letters 

 are structural details. 



the ''joint-worm" may do some damage, yet it is so easily con- 

 trolled that it scarcely affects the value of the family as a whole. 



The smallest of all our parasitic insects belong to the family 

 Prodotjypidce , and even the largest of them would be ordinarily 

 considered as small insects. Among them we find the greatest 

 number of egg parasites. As compared with the Chalcidids, 

 these insects are rarely metallic in color, usually black or brown, 

 sometimes yellow, and much more slender in build ; the body longer 

 in proportion to the thickness. Their habits may be said to be in 

 general like those of the other parasites, and they are not easily 

 distinguished from them, except by the special student ; but they 

 rarely have the geniculated antennae described for the Chalcidids. 

 None of these Proctotrypids are injurious, so far as we know, or 

 feed on vegetable matter, though some are found in galls, appar- 

 ently parasitic upon the original gall-maker. 



Taken as a whole, the parasitic Hymenoptera belonging to 



