HALICTUS. 421 



c'. Abdomen densely punctured. 



a\ Mesoaotum glabrous S ta>yhrs v 42o 



i^ Mesonotum closely punctured. ... JL das,,y aster, p. 4Jo. 



b. Head and thorax obscure blue H. alphenus, p. 4-b. 



c. Head and tliorax metallic green. 



a'. Length 9-10 mm H gmndwep., p 426. 



6'. Length 37-4 mm li- vachaln, p. 42b. 



B. Enclosed space at base of median seg- 



ment with transverse strife H. discursus, p. 427. 



0. Enclosed space at base of median segment 

 with longitudinal strise. 

 a. Head and thorax black. 



a'. Abdomen more or less punctured, 

 a^. Bases of abdominal segments 2-6 



constricted if. ^zzZc/mmzfm, p. 427. 



b^. Bases of abdominal segments not 

 constricted. 

 a\ Bases of segments 2-4 with pu- 

 bescent bauds, 

 o*. Front with a vertically im- 



pressed line -H"- ^oi^i^s, p. 428. 



6*. Front without a vertically 



impressed line or groove. ... H. subopacus, p. 428. 

 b^. Margins of abdominal segments 



1-5 with pubescent bauds .... J£. taprohanm, p. 428. 

 c'. Abdominal segments nearly bare, 



apical segments with afewde- _ 



cumbent hairs _• • • -&• lucuhmculus, p. 42 J. 



f?''. Second and following abdominal 

 segments coveredwith short fine 

 pubescence not forming trans- 



verse bands -H"- agrestis, p. 429. 



fc'. Abdomen impunctate. 



dK Basal two abdominal segments 

 with a faint but distinct transverse 



impressed line H- thmdus, p. 42J. 



b\ Basal two abdominal segments 

 without any transverse impres.sed 



liues 11. (/uthiroius, ]). ^^0. 



b Head and tho"rax metallic green H. propinquus, p. 430. 



c. Head and thorax metallic blue H. vernalis, p. 43U. 



D. Enclosed space at base of median segment 

 punctured. 



a. Head and thorax seneous or metalhc 



green. 

 a'. Base of 2nd abdominal segment 



strongly depressed and constricted . H. buccinus, p. 4oi. 

 6' Base of 2nd abdominal segment not _ 



constricted If. ?«««««, p. 431. 



b. Head and thorax black, often with a 



castaneous or chalybeous hue, or black 

 and red. 

 a' Abdomen smooth, impunctate. . 



d\ Abdomen eutii'ely black //• spodiozomus, p. 431. 



