538 NATURAL HISTORY OF ARTHROPODS. 



beneath the head and breast when not in use. They may be divided, according to 

 their economy, into social bees, solitary bees, and parasitic bees. There is not, how- 

 ever, with this family, as with the Vespidae, a ready separation into structural groups 

 corresponding with the three classes founded upon economy. The ordinarily accepted 

 classification throws the species into five sub-families. From the latest catalogue it 

 is seen that over seven hundred North American species of this family have been 

 described, showing our bee fauna to be richer than that of Europe. 



The sub-family Andrenoinae consists of species closely allied to Andrena. In this 

 group the labium is shorter than the meiitum. The maxillary palpi are six-jointed. 

 The females have no pollen-brush on the under side of the abdomen, but are furnished 

 with one on either side of the metathorax, and the legs also have such brushes. In 

 habits, also, these insects much resemble Andrena, excavating burrows and storing up 

 pollen and honey in a similar manner. Panurgus banksianus forms large colonies in 

 retired sandy places in England, burrowing to a depth of six inches, and making its 

 appearance in July. All of the North American species are western. 



The species of the sub- family Cuculinje form a well-marked group of naked, some- 

 times wasp-like, parasitic bees. They are destitute of polleniferous brushes and plates, 

 and from their structure were supposed to be inquilines before their habits AVCIV 

 definitely ascertained. ^\\>nt<!<(- is a genus of large extent, and its species lay their 

 eggs in the cells of Andrena and Jfalictus as well as of some of the higher bees. Thev 

 differ greatly in appearance from their hosts, yet seem to be on perfectly good terms 

 with them, visiting flowers in their company and entering their burrows as uncon- 

 cernedly as though they were the result of their own labors. Conjecture has been 

 rife as to whether the egg of Nomada is deposited only in those pollen masses not 

 already supplied by its host ; or whether, the opposite being the case, the larva of the 

 host is starved to death for the want of the food eaten by the earlier hatching Nomada 

 larva; but the observations of Emerton seem to show that the food supply is suf- 

 ficient for both larva j , which live harmoniously together in the same cell, and issue at 

 about the same time. The widespread Nomada imbricata is found in the nests of both 

 Andrena vicina and Halictus paraUelus. The larva is smooth, round, tapering towards 

 each end, and has a small head. The pupa has three conspicuous spines on the upper 

 and posterior edge of the orbit, which seem to aid in locomotion. The bees of this 

 genus are often captured with masses of clay attached to their posterior tibiae, with 

 which, it is surmised, they close the cell of their host after ovipositing. With the 

 other genera the habits are the same. Celioxys is parasitic in the cells of Megachile 

 and /Saropoda, Epeolus lives similarly on Colletes, Melecta on Anthophora, and Stelis 

 on Osmia. 



The sub-family Dasygastrinae contains many insects of interest. They derive their 

 name from the very large pollen brush which covers the ventral aspect of the abdo- 

 men. Pollen plates, however, are lacking. The labium is large and oblong, the 

 mandibles are particularly strong, the maxillary palpi are but slightly developed, and 

 the labial palpi are very long. The majority of the species bore in wood, and make 

 their cells of moist earth or of bits of leaves cut by the mandibles to a proper form. 



The species of the genus Osmia are called " mason bees," from the material of 

 which their cells are composed. The greatest possible diversity is seen in the situa- 

 tions in which, these are placed, and the bees show r a high order of intelligence in the 

 manner in which they adapt themselves to circumstances. Frederick Smith says : " If 

 I were asked which genus of bees would afford the most abundant materials for an 



