510 



NATURAL HISTORY OF ARTHROPODS. 



Fl6. 635. — Ulicdites rosce, rose gall-fly. 



tion." Mr. Adler has shown, however, that in Hhodites rosce, the fly of the common 

 rose gall, and in Rhodites eglanteridB there is a manifestation of atavism, thus confirm- 

 ing the bands which exist between the sexual and organic 

 states. "Although reproduction among them has become 

 entirely parthenogenetic, yet at times males apjsear, al- 

 though probably no copulation has taken place for a long 

 period." 



There are several genera of gall-flies which, although 

 they live in galls, do not produce them. These are 

 known as guest gall-flies or inquilines. The adult in- 

 sect lays her eggs within galls which have already been 

 formed by other insects. In some instances at least, the 

 guest does not starve nor injure the owner of the gall. 



In a third section of this family the insects are true parasites, living within the 

 bodies of other insects. The habits of these species resemble those of the Chalcididse. 

 The family Chalcidid^ is an immense group composed almost entirely of parasitic 

 species. Kirchner, in 1867, enumerated twenty-four hundred and seven European 

 species ; and although less than five hundred 

 North American species have been described, 

 an examination of the larger collections leads 

 us to the conclusion that the North American 

 fauna in this family is still richer. In general 

 the species are small in size, the largest {Leu- 

 cospis and Smicra) not exceeding tlie common 

 honey-bee, while the smallest species {Poropoea 

 and TrichogrammcC) are frequently not more 

 than a quarter of a millimeter in length. In 

 color they are nearly always black with strong 

 metallic reflections ; but many yellow species are known, and even red is often found 

 in the markings of the larger species of the genera Spilochalcis and Smicra. 



The species are all active and essentially diurnal in their habits. The body varies 

 greatly in form, as shown in the accompanying figures of several species parasitic upon 

 scale insects. The difference between the sexes is often very marked, and a striking 

 example of this is seen in Tomocera californica, both sexes of which are figured. This 

 species is parasitic upon Lecanium olece, the "black scale" of California, and the 

 male might readily be taken for a species of a different genus without positive evidence 

 to the contrary. 



In general the head is large, becoming enormous in Caratomus and allied genera, 

 and is carried at right angles to the body. The number of antennal joints varies from 

 seven to thirteen, and there is the greatest possible diversity in the character of the 

 flagellum. The eyes are large, and the ocelli are so placed as to form a triangle. In 

 certain genera of the very abnormal group of fig-feeders, Aoffonidce, the ocelli are 

 wanting, and in Eupristina both eyes and ocelli are absent. The thorax is highly 

 developed, and the wings, although large and strong, are nearly destitute of veins. 

 Many species lack the wings entirely. The ovipositor is usually hidden, though in the 

 sub-family Toryminse it is exserted and very long, and is used to penetrate galls. 

 In the genus Leucospis the ovipositor is curved up over the dorsum of the abdomen 

 to the thorax. 



Fig. 636. — Smicra maritR. 



