180 BRITISH BEES. 



bring the male within the boundary of the genus, nothing 

 but experience, or specific description will associate the 

 sexes correctly, there being in many cases an extraordi- 

 nary discrepancy between them. These two genera 

 themselves also can scarcely be distinguished apart, ex- 

 cepting by means of their trophi ; Cilissa, however, in 

 general habit greatly resembles the genus Colletes, espe- 

 cially the Cilissa tricincta, which might, upon a super- 

 ficial glance, be almost mistaken for one of them. 



The male Halicti have long cylindrical bodies and 

 long antennae, but from the male Chelostoma, which has 

 a very similarly shaped body also and long antennse, 

 they may be distinguished by the differences in the num- 

 ber of the submarginai cells ; and from those of Sphe- 

 codes, by the antennae, which, in the latter are not rela- 

 tively so long, and are usually moniliform. The thorax 

 of these is also less pubescent, and the tinge of the red 

 colour of their abdomen is different from that of the red 

 male Halicti. 



The males of Ccelioxys can be readily distinguished 

 from those of Megachile, by the spinose apex of their 

 abdomen. In Megachile, general habit will bring the 

 males within the precincts of their genus, as well as their 

 largely dilated anterior tarsi in some of the species. 



A difficulty similar to what is found in the distinction 

 between Andrena and Cilissa, arises in the separation of 

 Chelostoma from Heriades, and which we shall again 

 meet with in drawing the line between Anthophora and 

 Saropoda. The difference can only be detected by ex- 

 amining the trophi, but a pin and a little patience will 

 elucidate the separation. The males in all but two 

 species of Anthophora may be readily associated with 

 their partners ; but in these two the females are entirely 



