366 COLLEGE ZOOLOGY 



phaga grossorum, is held responsible for the fertilization of 

 the fig. 



The gall-flies (CYNIPID.E, Fig. 307) are small, dull-colored 

 insects possessing a long ovipositor with which eggs are laid in 

 plant tissue. In some way the plant is stimulated so that an 

 abnormal growth, called a gall, is produced. The young gall- 



FIG. 307. Order HYMENOPTERA. A, gall-fly, Rhoditcs rosa, female. 

 B, galls produced by a bug. (A, from the Cambridge Natural History, 

 B, from Davenport, after Kerner.) 



fly is protected by the surrounding tissue. Many species are 

 parthenogenetic, and only females are known. 



The bees (APID^:) comprise a large family, of which the honey- 

 bee is the best-known example. All grades of social life are 

 exhibited by bees. The leaf-cutter, Megachile acuta, is a solitary 

 species; she lays her eggs in leaf-lined cavities in wood, places 

 pollen and nectar in the cavities for the larvae to feed on, 

 and then flies away never to return. The carpenter bee, 

 Ceratina dupla, is also a solitary bee, but she watches her 

 young until they mature. Certain mining bees, e.g. Andrena, 

 lay eggs in burrows in the ground (Fig. 309, B). They are 

 solitary bees but often build their tunnels close together, 

 i.e. they have a tendency toward a gregarious habit. The 



