270 The American Naturalist. [March, 



nervures, tegula?, knees, tibiae at tips, and tarsi pale testaceous; one 

 specimen shows the nervures as pale as in female, the other has them 

 much darker. Length 6 mm. 



Illinois: 9 9,2 £ specimens, taken from May 19 to June 25, on 

 flowers of Oxa/is coniicahitn, MeJUotji* <tli>a, Scutellaria parvula and 

 Tradescantia virgin ica. 



In size, color of pubescence and wings this species closely resembles 

 H. aUripmws. It is distinguished from that species by its face, which 

 is longer, a little more sparsely punctured, its mesothorax more closely 

 and finely punctured, its metathorax less rugous, its abdomen green 

 and not depressed. 



5. Halictus cephalicus. $ —Smooth and shining, clothed with 

 very thin pale pubescence, head greenish, thorax blue-black, abdomen 

 brownish; head very large, wider than thorax, strongly produced 

 behind eyes, especially the cheeks below ; face subquadrate, finely and 

 sparsely punctured; clypeus transverse, truncate; labrum broad, 

 short, pointed; mandibles long, ferruginous, except base; flagellum 

 testaceous beneath towards tip ; prothorax forming a lateral dentiform 

 angle, mesothorax blue-black, shining, sparsely and minutely punc- 

 tured, appearing impunctate ; metathorax black, strongly retracted 

 and strongly sloping, so that it presents a very small truncation, the 

 latter heart-shaped, being divided above by a fissure ; wings hyaline, 

 nervures and stigma testaceous ; legs blackish, knees, tibiae at tips and 

 tarsi testaceous ; abdomen brownish, impunctate, apical margins of 

 segments testaceous, the segments clothed with thin, pale pubescence. 

 Length 6 mm. 



S . — Resembles the female, but does not show the peculiar head 

 characters, clypeus somewhat produced, metathorax rougher above and 

 bordered on each side by a ridge. Length 5 mm. 



Illinois: 19,2£ specimens, taken July 15 at a bank which was 

 filled with nests of H. zephyrus. The sexes were taken in copula. 



This species may be easily distinguished by the shape of its head, 

 which i3 much like that of the 9 of H. ligatus Say (^(irmotireps 

 Cress., texanus Cress., nrmdipes Cress., capitoms Sin.). 



6. Halictus obscurus. 9 —Form rather slender, head and thorax 

 dark blue-green, abdomen black, clothed with thin pale pubescence; 

 face round, the clypeus somewhat produced ; mesothorax minutely 

 roughened but shining, sparsely punctured, the pubescence thin; 

 metathorax rather narrow, stn>ngl_\ retracted, truncate, with several 



