BEES OF BOULDER COUNTY, COLORADO 253 



narrow (Boiilder, fls. Pulsatilla hirsutissima, April 20, W. P. Ckll.) pulsatills Ckll. 

 Hair of thorax without black hairs interspersed (Boulder, April 20, fls. Pulsatilla 

 hirsutissima) aprilina Ckll. 



MONUMETHA Cresson 

 Black with parallel-sided abdomen; face of male with appressed white hair (Ward, 

 fls. Phacelia and Frasera) .... albifrons Kirby (argentifrons Cresson) 



ALCIDAMEA Cresson 

 Black, about 7 mm. long; male with very thick flagellum (Boulder, fls. Phacelia) 



simplex Cresson 

 Graenicher found this species nesting in dry stems of blackberry, etc.] 



ASHMEADIELLA Cockerell 

 Female length 6 to 7 mm.; head and thorax black; abdomen black, with first 

 dorsal segment red except a central mark, second red at sides, third partly red 

 (Fort Collins) gillettei Titus* 



HERIADES Spinola 

 Length 8 mm. or over; black; mandibles of female with a tubercle on outer side; 

 ventral scopa white (Boulder, fls. Clematis ligusticijolia, July, W. P. Ckll.) 



gracilior Ckll. 



LITHURGUS Berthold 

 Large, Megachile-\\]Lt; apex of female abdomen with red hair, of male abdomen 

 sharply pointed (Boulder, fls. Opuntia) apicalis Cresson 



MEGACHILE LatreiUe 



Females i. 



Males II. 



1. Abdomen without bands; first two dorsal segments and base of third with light 



hair, the others with black; scopa red 2. 



Abdomen with more or less conspicuous hair-bands 3. 



2. Little or no black hair on vertex and mesothorax (Boulder, Aug., W. P. Ckll.) 



wootoni Ckll, 

 With conspicuous black hair on vertex and mesothorax (Ward, fls. Lupinus) 



wootoni calogaster Ckll. 



3. Cheeks with an enormous tooth beneath; mandibles greatly elongated (Boulder, 



Ward, fls. Geranium, Carduus) pugnata Say 



Not so 4. 



4. Ventral scopa largely or wholly red or orange 5. 



Ventral scopa white or creamy-white, with or without black at extreme apex 



7. 



5. Smaller, length less than 12 mm.; head and thorax above with some conspicuous 



black hair (Boulder, September, Rohwer) relativa Cresson 



Larger, length over 13 mm 6. 



6. Abdomen heart-shaped; hair of mesothorax mainly grayish-white (Ward, South 

 Boulder Canyon, Boulder; fls. Phacelia, Senecio, Psoralea, Grindelia) latimantis Say 



