1S(U.] 17 



On the North American species of the genus OSMIA. 

 BY E. T. CRESSON. 



Genus OSMIA. Latr. 



••The labial palpi tour-jointed, the basal joint elongate, the second nearly 

 twice as long, the third and fourth minute, the third inserted at tlie aj^ex of 

 tlie second, the fourth at the apex of the third, the two latter elavate, truncate 

 At their aj^ex. The maxillary palpi four-jointed, the basal joint stoutest, broad- 

 est at the base, about the same length as the second and third joints, the apical 

 joint minute. The superior wings with one marginal and two submarginal cells, 

 the second submarginal cell receiving the two recurrent nervures. 



•• In tlie female the head is usually very large, subquadrate, the ocelli placed 

 forward on the vertex in a sliglit curve; the abdomen furnished with a dense 

 l)ollen-brush beneath. 



" Males usually reseuxbling the female, but more slender, having the antennae 

 longer, and the apex of tlieir al)domen generally armed with spines or teeth." — 

 Smith, Bees of Great Britain, p. 1.57. 



The bees of this interesting genus are generally of a bluish or green- 

 ish color, having a short, robust form, more or less pilo.se, the head 

 large, especially in the females, and the abdomen mostly subglobose. 

 A very interesting account of the economy of these bees is given by 

 Mr. Smith (Ibid. pp. 158—162). 



In this paper I have 33 North American species to record, all i)f 

 which are known to me except two — 0. frigida Smith, and 0. hurco- 

 lu's Say. In separating the closely allied species, I have relied much 

 on the difference of sculpture and punctatiou, which seems to be very 

 constant in the same species, although when more material has been 

 accumulated, we may find intermediate grades of variation that will 

 make varieties of some that are now considered distinct species. 



1. 0. bucephala. n. sp. 



Female. — Head very broad, subquadrate, as large as the thorax, 

 black with a slight bluish-green reflection, densely and finely punc- 

 tured, clothed with rather long pubescence, which is black on the 

 clypeus, dense and ochraceous about the insertion of the antennae, 

 sparse on the vertex, and dense and fuscous on the cheeks beneath; 

 apical uuirgin of the clypeus suddenly, strongly and squarely produced 

 in the middle, and fringed beneath with a short fulvous pubescence, 

 the lateral angles of this projection are obtuse but prominent; on each 

 side of the clypeus immediately above the base of the mandibles a 



