108 HYMENOPTERA. 



Habitat. — Apparently the whole of North America from 

 Mexico well into Canada, at all altitudes. Recorded on 

 flowers of Cleonie, Mentzelia, Fragaria, Tamarix, Me7itha, 

 Solidago, Avtorpha, Melilotus, Grindelia, Astragalus^ Drymo- 

 caliis, Bigelovia, Wild Phcm, Salix, Sisymbi^ium, and Clematis. 



Specimens examined: 500-600 males, and 400-500 females, 

 from Calif., Colo., Nev., N. M., Ariz., Neb., Wise, Mich., 

 111., Me., Cana., etc. 



The variations in this little species are astounding. I have 

 before me over one thousand specimens from widely sepa- 

 rated localities all over the United States, and parts of 

 Canada, including very large series from many of these 

 localities, and among them all sorts of modifications are 

 found. The species is, I believe, the most common in 

 America, as it is most often represented in local lists, and 

 forms a considerable part of most collections. Covering 

 such an area as it does, and being subject to such different 

 conditions, it is only natural that many variations should be 

 found. Extremes of these variations, if taken alone, would 

 be considered distinct species at once, and it is only in an 

 enormous series that the intergradations become evident, 

 and distinctive characters vanish. An idea of the variations 

 in color characters in the species can be obtained from figures 

 77-83 and 124-129, which indicate a few of the steps from 

 the strongly, clearly marked forms to the poorly marked, or 

 wholly dark ones. To be complete the series should include 

 many more of the intermediate forms, but those given will 

 serve to illustrate the range of variation. In nearly all char- 

 acters of both sexes a similar degree of variation is found. 

 The puncturation varies all the way from that of the typical 

 form as given, or even more dense, to very faint, indistinct 

 punctures in some specimens. In none, however, is the ab- 

 domen densely, coarsely punctured, as it is in some other 

 species ; at most the first two or three segments are moder- 

 ately punctured. 



The form mesillce is found mostly in New Mexico, Arizona, 

 and the surrounding States, apparently being a southern 

 form. It can only be distinguished by its color markings. 



