90 PROCEEDINGS OF THE ACADEMY OF [1896. 



having no band. Venter pale yellowish, slightly orange toward 

 the tip. 



Hab. — Las Cruces, IST. M., one specimen on Bigelovia ivrightil, 

 close to the Agricultural College, Sept. 12, 1895. (Ckll. 5,100). The 

 type specimen may be a little immature, but it is clearly distinct. 



Small species found on Bigelovia tvrightii,the abdomen not banded. 

 51. Perdita fallax n. sjj., or race. 



9 . — 5 mm. long. Head and thorax dark green, dullish, rather 

 hairy but the hairs short, face below antennae bare and shining. 

 Head of ordinary size, rounded, not broader than long, occiput and 

 cheeks well fringed with short hairs, vertex granular. Clypeus 

 moderately high, flat above, with the sides very narrowly produced. 

 Face-markings yellowish-white ; clypeus all pale except the two 

 usual dots, and two dots near the upper margin, representing the 

 ends of the bars seen in some species, or the bars may be even 

 fairly well-developed. Supraclypeal mark absent, though there 

 may be a pair of scarcely perceptible pale specks close to upper 

 border of clypeus. Dog-ear marks absent. Pale lateral marks at 

 first rapidly narrowing, and then gradually, ending in a narrow 

 truncation at the level of the antennte. Cheeks dark, mandibles 

 rufous at tips. Autennre dark brown, yellow beneath, the sutures 

 of the flagellar joints dark. 



Mesothorax minutely lineolately sculptured. Pleura all dark. 

 Tubercles and two spots on hind border of prothorax white. Teguhe 

 hyaline subtestaceous. Wings hyaline, nervures and margin of 

 stigma sepia-brown. Marginal cell appendiculate, poststigmatal 

 portion a little the longest. Second submarginal large, narrowed a 

 little more than one-half to marginal ; od discoidal distinct. Legs 

 brown-black ; anterior knees and anterior tibia? in front pale prim- 

 rose-yellow. Middle and hind knees whitish. 



Al)domen rather broad and flat ; above piceous, with an oblique 

 white mark on each side of segments 1-3, those on 1 very narrow 

 and closely approximating in the median line. Tip orange, or to 

 be more precise, the pygidium is orange with the border colorless 

 and hyaline, the tip emargiuate, as is also the case in affinis. Ven- 

 ter piceous. 



Hab. — Las Cruces, N. M., on Bigelovia ivrightii, Sept. 23, 1895, 

 two specimens (Ckll.). This is, in all respects, very closely allied to 

 P. affinis, but it is smaller, the abdominal markings are white and 



