116 BRITISH BEES. 



pedes or naked-legged, from their not having the neces- 

 sary apparatus of hair upon the posterior thighs or shanks, 

 for the conveyance of pollen wherewith to store their 

 nests. Thus nature, having rendered them unable to 

 perform this duty to their offspring, has imposed upon 

 them the necessity of resorting to strangers to support 

 them, and they are not led to it by idleness or indifference, 

 These insects consist, with us, of six genera, the species 

 of which are individually attached to some particular 

 bee, who thus nurtures their young. They are, as a rule, 

 gayer insects than those which they infest, and the genus 

 most abundant in species is Nomada, which attaches 

 itself chiefly to Andrena, although some of its species, 

 especially the smaller ones, infest the species of Halic- 

 tus, and one frequents Eucera. Melecta appears confined 

 to Anthophora ; Epeolus to Colletes ; Stelis perhaps to 

 Osmia, judging from the great similarity of habit ; and 

 Coelioxys to the constructive Megachile. None of these 

 parasites resemble their sitos, but Nomada is exceed- 

 ingly different, being in its gay array more like a wasp 

 than a bee. The only close approach in the appearance 

 of a parasite to the insect upon which it is parasitical is 

 in the resemblance between Apatlms and Bombus, which 

 are so alike that they were long continued to be united in 

 the same genus, until the peculiar characteristic of the 

 parasitical bees was detected, when they were readily se- 

 parated. Although, cuckoo-bees as they are familiarly 

 called, they could not be associated with the Nudipedcs, 

 because their posterior legs, though not pollen-conveying 

 organs, are hairy ; but the Cenobites, to which section 

 they belong, have a peculiar and distinguishing structure 

 of that limb. They are further separated from the Nudi- 

 pedes by several frequenting the same nest, thus habi- 



