HYMENOPTERA 349 



common in some parts of South America; it can be recognized by the 

 venation of the wings, which is similar to that of the female. This species 

 is parasitic on the larva? of May-beetles. 



Family Cynipids 

 The Cyuipids 



Most members of this family are small insects and many of them are 

 minute; for this reason they are not commonly observed; but the galls 

 produced by some species, especially those that are found on oaks and 

 roses, are very familiar objects. Not all cynipids, however, produce galls; 

 some are parasites and others are inquilines, living in galls produced by 

 other species. 



The antennae of the cynipids are not elbowed and only rarely com- 

 posed of more than sixteen segments; the 

 pronotum is produced on each side so as 

 to reach the tegula or is separated from it 

 only by a membranous area; the wings 

 lack a stigma and have at most five closed 

 cells; the wings are rarely wanting; the 

 abdomen is strongly compressed. 



In most of the cynipids the dorsal 

 sides of the basal segments of the abdo- 

 men are very long and appear to project 

 over and cover the last segments so that 

 only the edges of the latter are visible (Fig. 



p q 2 ) Fig. 592. — A mpliibolips. 



The cynipids are of interest because some of them are parasitic on 

 other insects, especially aphids and the larvae of flies, and because some 

 cause galls on various plants. 



The work of the gall-producing species is much more conspicuous 

 than that of the parasitic forms and more is known about the gall-makers 

 which are commonly known as gall-flies. It should be remembered, how- 

 ever, that galls on plants are produced by other insects, namely, plant- 

 lice, flies, moths and occasionally beetles and also by mites. In the case 

 of galls made by the cynipids the gall is closed and a hole must be made 

 by the insect in order to emerge. Moreover, there is no reproduction of 

 insects within the galls of gall-flies, as there is within the galls of mites 

 and plant-lice. 



It is a remarkable fact that each species of gall-insects infests a special 

 part of one or more particular species of plants, and the gall produced by 

 each species of insect is of a definite form. Hence when an entomologist 

 who has studied these insects sees a familiar gall, he knows at once what 

 species of insect produced it. 



Naturalists have speculated much as to the way galls are made to 

 grow. It has been supposed that at the time the egg is laid there is 

 deposited in the tissue of the plant with it a drop of poison, which causes 

 the abnormal growth. By this theory the differences between the galls 

 of different insects was explained by supposing that the fluid produced 

 by each species of insect had peculiar properties. There are certain 

 kinds of galls which may be produced in this way. Thus it is said that 



