208 



HYMEXOPTEEA. 



blossoms, which act, as applied to this instance of the fertiliza- 

 tion of flowering plants by insects, has been called by Mr. 

 Westwood " caprilication." 



Cynipidje Westwood. {Dijilolepariai Latreille.) Gall-flies. 

 In this most interesting family we have a singular combination 

 of zoological and biological characters. The gall-flies are closely 

 allied to the parasitic Chalcids, but in their habits are plant- 

 parasites, as they IIa'c in a gall or tumor formed by the ab- 

 normal growth of the A'Cgetable cells, due to the irritation first 

 excited when the egg is laid in the bark, or substance of the leaf, 

 as the case may be. The generation of the summer broods is 

 also anomalous, but the parthenogenesis that occurs in these 

 forms, by which innneuse numbers of females arc produced, is 

 necessary for the work they perform in the economy of nature. 

 When we see a single oak hung with countless galls, the work 

 of a single species, and learn how numerous are its natural 





enemies, it becomes evident that the demand for a great nu- 

 merical increase muct be met by extraordinary means, like the 

 generation of the summer broods of the Plant-lice. 



The gall-flies are readily recognized by tlieir resemblance to 

 certain Chalcids, but the abdomen is much compres!-ed. and 

 usually very short, while the second, or the second and third seg- 

 ments, are greatly developed, the remaining ones being imbri- 

 cated or covered one by the other, leaAing the hind edges 

 exposed. Concealed within these, is the long, partially coiled, 

 very slender ovipositor, which arises near the base of the abdo- 

 men.* Among other distinguishing characters, are the straight 



*Fig. 142. I, iibdomen of Cynip.t quercus-aciculnfa Ostcn Sarken. Avith the ovii)os- 

 itor exserted ; II, the same with the ovipositor retracted ; III, the abdcnioii of the 

 female of Fif/ites (Diplolepis) it-lineatus Say; IV. the same showing: the ventral 

 portion, in nature covered by the tergal portion of the ab<lomcn ; V, end view of the 



