THE BEES OF BOULDER COUNTY, COLORADO 



By T. D. a. Cockerell 



The bee-fauna of Boulder County has proved remarkably rich and 

 interesting, yielding a considerable percentage of new species. It is, of 

 course, very far from being exhausted, but the following tables are offered 

 as a means of facilitating further progress. Various species, especially 

 of the genus Halictus, are for the present omitted, as they cannot be 

 identified until our studies of the genera they belong to have progressed 

 further. Many species of Halictus, Osmia, and Andrena have been sent 

 to Messrs. Crawford, Titus and Viereck respectively for investigation, 

 but nothing has been learned concerning them. They will doubtless be 

 discussed in forthcoming works by these apidologists. 



The list, as it stands, numbers about 175 species. In the vicinity of 

 Carhnville, Illinois, Robertson appears to have found about 275, after 

 years of careful collecting. Owing to the varied conditions represented 

 in Boulder County, it is not unlikely that the total number of species 

 existing considerably exceeds 300. I have inserted in the tables a 

 number of species likely to occur with us, but not yet actually found. 

 These are distinguished by an asterisk. At some later date, I may offer 

 a discussion of the families and genera of bees ; but this does not seem 

 very necessary at present, owing to the existence of several works cover- 

 ing the ground, more especially those of Robertson and Ashmead 

 {Trans. Amer. Entom. Society, 1899; Canadian Entomologist, Feb., 1904, 

 etc.). Cresson's Synopsis (1887), though old, is still very useful for 

 determining the genera. 



COLLETES LatreiUe 



Comparatively large (length of anterior wing about 8 mm.), hair of thorax above 

 fox-red, especially bright on scutellum, without any black intermixed (Boulder, 



fls. Heuchera) andrewsi Ckll. (simulans, Cress., in part)$ 



Not so large; hair of thorax above not thus bright i. 



I • Hair of head and pleura black (Ward, July, fls. Drymocallis) . nigrifrons Titus 

 Hair of head and pleura light 2. 



2. Some dark hair on thorax above, at least on scutellum 3. 



No dark hair on thorax above 4. 



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