HYMENOPTERA 



927 



and branches of the Cah'fornia white oaks, and during the winter, 

 when the trees are bare, it is a very conspicuous object, on account 

 of its abundance and large size. It varies in shape from globose to 

 reniform and also varies greatly in size, some of the larger ones 

 measure more than loo mm. in their greatest diameter. The outer 

 surface of the gall is white and usually smooth ; the interior is more 

 or less filled with a compact soft material, and contains from one to 

 a dozen larval cells. Several varieties of the gall-fly that produces 

 this gall are described by Kinsey ('22). 



The mossy rose-gall, Rhodltes rosce.- — ^This is a very common poly- 

 thalamous gall, which is formed on the stems of rose bushes, especially 

 of the sweetbrier. The gall consists of a large mass of moss-like 

 filaments surrounding a cluster of hard kernels (Fig. 1 164). In each 

 of these kernels a gall-fly is developed. The galls appear early in the 

 summer but the adults do not emerge till the following spring. These 

 are male and female; there is no alternation of generations in 

 this species. 



SuPERFAMiLY CHALCIDOIDEA 



The Chalcid-flies 



This superfamily is the larg- 

 est in number of species of the 

 superfamilies of the Hymenop- 

 tera, including many thousand 

 species. Most of the species are 

 very small insects and some are 

 minute measuring not more than 

 aquarter of a millimeter in length ; 

 some species are much larger but 

 these do not exceed the honey-bee 

 in size. Most of the species are 

 black, with strong metallic re- 

 flections, although some are yel- 

 low and some of the larger species 

 have red markings. The head is usually large (Fig. 1165) ; the pro- 

 thorax does not extend back on 

 each side to the tegula; the ve- 

 nation of the wings is greatly re- 

 duced; and the ovipositor is usu- 

 ally hidden; issuing before the 

 apex of the abdomen, but in some 

 genera it is very long. 



In most of the Chalcidoidea 

 the venation of the wings is re- 

 duced to the type shown in Fig- 

 gure 1 166; in a few, however, there are vestiges of other veins; but 

 in none are there anv closed cells. 



Fig. 1 165. — A chalcid-fly, Aphycus 

 emptor. 



Fig. 1 166. — Fore wing of a chalcid-fly. 



