116 HYMENOPTERA. 



In the social Bees, besides the normal male and female forms, 

 there are asexual females, whose inner genital organs are partly 

 aborted, though externally only differing in their smaller size 

 from the true females. Tiie male antennae are longer, tapering 

 more towards tlie tips, and the eyes of tlie male approach each 

 other closer over the vertex than in the opposite sex, though 

 these are characters wliich ai)ply to other Hymenoptera. The 

 mouth-parts are in the higlier genera greatly elongated, the 

 labium being long, with tlie lingua of great length, and the 

 lobes of the maxilhe long and knife-shaped ; but these parts, as 

 well as the form of the jaws, are subject to great modifications 

 in the different genera : the labial palpi are four-jointed, and 

 the maxillary palpi are from one to six-jointed. The hind 

 tibia and basal joint of the tarsi are, in the pollen-gathering 

 species, very broad ; the tibia is in Apis and Bombus hollowed 

 on the outside, and stiff bristles project over the caA'ity from 

 each side of the joint, forming the hone^'-basket (corbicuhnn), 

 on which the "clodden masses of honey and pollen" are con- 

 veyed to their nests. In the parasitic genera, such as Aixithiis, 

 the tibia is, on the contrary, convex, rather than concave, 

 though of the usual width ; while in Nomada, also parasitic, 

 the legs are narrow, the tibia not being dilated. 



In Andrena and its allies, Ilalictiis and CoUetes, the mouth- 

 parts, especially the tongue, are much shortened, thus afford- 

 ing a passage into the Vesjiidce . In these genera the tongue 

 is folded back but once between the horny encasement of the 

 maxillae, but in the higher Ajiiarice the part formed by the 

 union of the lingua and maxilla is twice bent back, and thus 

 protected by the horny lobes of the maxillae. The fore- wings 

 have two or three subcostal (cubital) cells. 



There are two thousand species of this family. The differ- 

 ences between the larvai of the various genera of this family 

 are very slight, those of the parasitic species are, however, 

 readily distinguished from their hosts. 



The higher Aplarioi, comprising the subfamily ^Ij^miob, have 

 the ligula long, c^dindrical, while the labial palpi have two 

 very long, slender, compressed basal joints, and two short 

 terminal joints. 



The genus A^ns has no terminal spurs on the hind tibiae, 



