THE HYMENOPTERA 347 



is a mass of radiating fibers and at the center a small cell in which the 

 insect lives. Protuberances of various forms on the leaves of many kinds 

 of plants are produced by different species of these insects. 



Gall insects are often not alone in their habitations. Some members 

 of the same superfamily as the gall-makers are frequently found in the 

 galls, living as " guests," profiting by the work of the producers of the 

 galls but not injuring them in any way. These are usually called in- 

 quilines and often greatly resemble their hosts. In addition to the 

 inquilines, parasites not only of the host but also of the various kinds of 

 inquilines may also be present, adding greatly to the population of the 

 gall. Some of these may be of the same superfamily as their hosts. 

 Kieffer lists 10 species of guests and 41 species of parasites which he 

 obtained from a root gall on oak, besides the gall maker itself! 



FIG. 363. Various types of Galls, about natural size. (Original.) 



Galls are not usually of any great economic importance, for though 

 they may injure the appearance of a plant or tree for two or three sea- 

 sons, and also check its growth somewhat, the abundance of parasites 

 usually stops the work of the gall makers before serious injury has been 

 accomplished. 



Superfamily Chalcidoidea (The Chalcid Flies) . This is an extremely 

 large group, containing thousands of kinds of insects, most of which are 

 very small, and a few are only about a fiftieth of an inch long. Some of 

 them live in galls, parasitic either on the gall maker or on inquilines: 

 others are parasitic on various insects, parasitizing the egg, larva or 

 nymph, pupa, or adult according to the species; and a few are plant 

 feeders of more or less economic importance. The wings, except in some 

 wingless species, have very few veins, the most prominent one running 

 out from the body about half way to the tip, then bending forward to the 

 costa, after which it bends back into the wing a short distance and ends. 



