some Bees from British Guiana. 445 



to be regarded as local races of widespread species. TIow far 

 this will be paralleled among the bees remains to be ^een. 

 The buttertiics and ants certainly show analogous phenomena. 

 Nevertheless, when we have defined a series of 8ui)speeies 

 and arranged them under aggregate species, the biological 

 problem has not been solved. Experimental work has shown 

 that objectively identical differences may be due either to 

 heredity or environment. Among the bees, it is probable 

 that the " little species '"' are in most cases the genuine units 

 of life, having different habits and occupying different 

 stations. It will, of course, be long before these matters 

 have been adequately elucidated by field-observations in 

 tropical countries, but every scrap of biological information 

 is of value. 



Aiigochlura {Odontochlora) essequibensis, sp. n. 



? . — Length about 11*5 mm. 



Robust, black and green ; head large, with broad rounded 

 cheeks and broad vertex, maiidy black, but a bright green 

 band along anterior orbits, and upper part of cheeks greenish ; 

 mandibles strongly bidentate, dark red in middle, with no 

 green spot at base ; clypeus broad, polished, witfi rather 

 numerous large punctures, its lower middle depressed, and at 

 each extreme side a distinct tubercle; supraclypeal area 

 very convex, dullish ; front very densely and minutely 

 rugoso-punctate ; flagellum ferruginous beneath, except at 

 base ; mesothorax very densely and finely rugoso-punctate, 

 median depressed line distinct; mesothorax black, with 

 green margins, and a pair of green bands converging 

 anteriorly; scutellum sculptured like mesothorax, black in 

 middle, green at sides, the median groove distinct ; area 

 of metathorax with about 55 delicate longitudinal stride, 

 irregularly connected about the middle by a transverse line; 

 ])osterior truncation not defined above ; postscutellum 

 brilliant green, and metathorax mainly green ; mesopleura 

 black, faintly greenish, granular; teguloG castaneous. Wings 

 dusky, stigma dark reddish, nervures dark; first recurrent 

 ncrvure meeting second intercubitus. Legs black, anterior 

 tibii\i red in front, at least at base; hind spur simple ; meso- 

 thorax with black hair, postscutellum, metatliorax, and base 

 of abdomen with white, inner side of tarsi with dark rufo- 

 fuscous hair. Abilomen almost impunctate, the first segment 

 with very delicate punctures at sides; abdomen broad, 

 black, sufi'nscd with green at sides^ with delicate pruinose 

 pubt'scetice, shiniuL; sdvery in some lights; a[)ex with black 

 hair; first ventral st^^^iiirnt with a long stout S[)ine. As in 



