748 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



North Haven, 3 August, 1905, on flowers of Pycnanthemum; 

 Westbrook, 30 August, 1904, on goldenrod (H. L. V.) ; Bran- 

 ford, 22 August, 1904 (H. W. W.). 



1 



C. sodalis Cresson. 

 C. lateralis Cresson. 



Osmia "Panzer. 



The bees of this genus are known as mason-bees, owing to 

 the fact that they construct nests of clay and sand in the inter- 

 stices of stone walls, old fence-posts, trunks of trees, etc. 



Key to Species. 



Females, 



1. Malar space distinct; ventral scopa black; face with or with- 



out some black hairs; that section of subdiscoidal vein 

 forming lower border of third discoidal cell longer than 

 principal section of vein separating first and secnd dis- 

 coidal cells 2 



Malar space wanting; mandibles simple at base 4 



2. Clypeus entire 3 



Clypeus with a large subquadrate emargination, with denti- 

 form lateral angles; malar space posteriorly with a large 

 compressed tubercle; mandibles with a large triangular 

 inner tooth; basal vein received beyond nervulus lignaria 



3. Clypeal margin produced and thickened; mandibles tridentate, 



with a transverse basal carina; basal vein received before 



nervulus bucephala 



Clypeal margin not thickened or produced; mandibles quadri- 

 dentate, with a transverse basal depression; basal vein 

 received a little beyond nervulus purpurea 



4. Front without tubercles 5 



Front with two tubercles, one above the other; mandibles tri- 

 dentate; clypeus with a shining, somewhat concave, edge; 

 basal vein not received before nervulus; scopa white .. 



conjuncta 



5. Ventral scopa white or yellowish 6 



Ventral scopa black; head with pale pubescence Q 



6. Scopa white; mandibles quadridentate or tridentate 7 



Scopa yellowish; mandibles quadridentate; basal vein re- 

 ceived before nervulus distincta 



7. Basal vein not received before nervulus 8 



Basal vein received before nervulus; clypeus rather distinctly 



