1896.] NATURAL SCIENCES OF PHILADELPHIA. 73 



marginal large, narrowed more than half to the marginal ; 3d dis- 

 coidal distinct. Legs yellow, tarsi pale testaceous ; spot on middle 

 femora and tibiae, a large blotch on hind femora, and hind tibiae 

 except basal third, black. 



Abdomen above lemon-yellow, the last segment slightly orange. 

 First segment with two black spots ; rather broad black bands at 

 hind margins of segments 1-4, intruding a little, especially at sides, 

 on the base of the segment following, not at all notched, nor joined 

 together. Venter yellow without bands. 



S . — Differs as follows : Scape with a small black stripe above. 

 Face below antennae all yellow, owing to the space beneath the 

 antennat being filled in by well-developed dog-ear marks, and to the 

 supraclypeal mark being higher. The lateral face-marks are rather 

 obliquely (not squarely) truncate, and are scarcely at all produced 

 along the orbital margin above the truncation. The frontal pale 

 spot is wanting. The collar is not yellow, and the yellow border of 

 prothorax is reduced to two marks, the tubercles also remaining 

 yellow. The nervures and stigma are dark brown, the marginal 

 cell is longer, and the second submarginal less narrowed above. 

 Legs black, with the knees and anterior femora and tibiae in front, 

 yellow. The abdomen is black, with orange or yellow clean-cut 

 interrupted bands on segments 1-4. Venter dark. The cheeks are 

 unarmed. 



Hab. — Fort Collins, Colorado, Aug. 15, 1895, on Solidago cana- 

 densis; one 9, one $ , sent by Mr. Baker. The S is so different 

 from the 9 , that it may be a distinct species ; but the face-markings 

 are exactly such as might belong to the sexes of a species, and there 

 are several points of similarity in structure. In a case of this sort, 

 one decides partly by the circumstances of the capture, the two sexes 

 having been taken from the same flowers on the same day. 



Three other species from Colorado, habits unknoicn. 

 28. Perdita snowii n. sp. 



9 . — Length 5* mm. Head and thorax dark brassy-green, dull 

 and granular, metathorax bluish and more shining. Head fairly 

 large, approximately round ; face very little hairy, although the 

 mesothorax and other parts of thorax are quite hairy, the hairs 

 being of a pale brownish color, dirty white on the under parts. 

 Mandibles stout, simple, yellowish with rufous ends. Antennae dark 

 brown, scape pale beneath. Clypeus, and sides of face rather nar- 



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