134 "^ Psyche [August 



A LIST OF THE BEES OF THE GENUS 

 PERDITA SMITH. 



By T. D. A. COCKERELL, 



The University of Colorado, Boulder, Colorado. 



The present list includes all the known species of Perdita, the 

 genus being confined to North America, and only well developed 

 in the arid southwest. The South American insects referred by 

 Friese to Perdita belong to Parafriesia, a genus scarcely separable 

 from Calliopsis. The Old World genus Nomioides has the closest 

 possible superficial resemblance to Perdita, but is structurally 

 quite distinct, having much in common with Halictus. The species 

 of Perdita are mostly very small, and practically all are oligo- 

 tropic, confining their visits to a single genus, or to a few closely 

 allied genera. Occasionally specimens will be found on plants of 

 quite diverse families, and this seems especially to occur when 

 the proper food plant is not yet in bloom. Most of the species 

 occur in late summer and autumn, but there is quite a series of 

 spring-appearing forms. I have never taken any species both in 

 spring and summer, but Mr. Viereck took P. phacelice in May 

 and June, and P. pedidis in April and May, at Alamogordo, New 

 Mexico, these being previously known as September bees. It is 

 not known whether the September brood hibernates and reappears 

 in spring, or there are two generations in the year. 



Subgenera and Sections. 

 CocKERELLiA Ashmead, Psyche, 1898, p. 284. Type hyalina. 



A name for the group of P. alhipennis, verbesince, sparsa, 



utahensis, etc. 

 Neoperdita Ashmead. The diagnosis seems to indicate species 



like P. sphcpralcecF, but the designated type is P. zebrata. 

 NoMADOPSis Ashmead. The assigned type was P. zonalis, but the 



specimens pertain to a different, undescribed species. 

 Philoxanthus Ashmead. Type P. beata. 



For Ashmead's characterization of the above four groups, 



see Trans. Amer. Ent. Soc, XXVI (1899), pp. 84-85. 

 Perditella Cockerell. Type P. larreae; also includes P. mar- 



cialis. For figure of venation see Proc. Acad. Nat. Sci., Phila., 



