Robertson — North American Bees. 351 



bis M. opliva $ from M. mendica $ by its smaller size and 

 absence of grooves on abdomen. M. mendica 5 varies in 

 length from 9-13 mm., some specimens being no larger than 

 small specimens of M. brevis. 



Megachile relativa Cress. 



Megachile relativa Cresson, Trans. Am. Ent. Soc. VII, 126, 9, 1878. 

 Megachile infragilis Cresson, Trans. Am. Ent. Soc. VII, 127, tf, 1878. 

 Carliuville, Illinois; five £, two $ specimens; $ Can., 

 U.S.; <?N. Y. (Cress.). 



The $ has the anterior coxae unarmed. 



Megachile 6-dentata Rob. 



Megachile 6-dentata Robertson, Trans. Am. Ent. Soc. XXII, 125, tf, 

 1895. 



5. — Black, very robust, opaque and densely punctured, the 

 vertex and abdomen a little more shining and more sparsely 

 punctured; sides of face, cheeks, thorax except the disc, 

 femora and basal segment of abdomen with rather long 

 white pubescence, on vertex, mesonotum, more or less, and 

 abdomen above short, thin and black; middle of clypeus 

 shining, with large rather sparse punctures; mandibles 

 stout; flagellum black or dull, testaceous beneath; wings 

 hyaline, a little clouded at tips and in marginal cell, nervures 

 black or fuscous, tegulae dull, testaceous exteriorly; legs 

 black, tarsi inclining to dull ferruginous with yellowish hairs 

 beneath, anterior aud middle tibiae at apex with a testaceous 

 deeply notched process, middle tarsi very broad, joints 1-3 

 with their anterior angles produced nearly the length of fol- 

 lowing joint ; abdomen broad, flat, basal segment widely and 

 very deeply concave, 2-3 transversely sulcate, 2-5 with nar- 

 row fasciae of white pubescence, apical segment without 

 erect hairs except on sides of base, the pubescence dense, 

 closely appressed, sericeous, becoming fuscous towards tip; 

 scopa white, apical ventral segment with hairs short, thin, 

 inclining to yellowish or fuscous, the apex broad, reflexed 

 behind the apex of dorsal segment. Length 13-15 mm. 



Carlinville, Illinois; six $, three $ specimens. 



The $ varies with the pubescence nearly white and the 

 apex of seventh ventral segment entire. 



