1895.] NATURAL SCIENCES OF PHILADELPHIA. 11 



SOME NEW BEES OF THE GENUS PERDITA. 

 BY T. D. A. COCKERELL. 



In Cresson'*s catalogue of 1887, there are given thirteen species of 

 Perdita, four of which, however, are considered only doubtfully 

 referable to the genus. Of these species 2 are from Col., 2 Cala., 

 2 Nev., 1 Tex., 1 Col., Nev., 1 Col., Tex., N. Mex., 1 Ga., 1 U. 

 S., IN. Am. Lately, Mr. Fox has described three from Lower 

 California. The opinion, which might have been derived from these 

 facts, that the genus is specially characteristic of the arid region, is 

 strengthened by the information given below. Without any special 

 search for the genus, the writer has discovered ten new species in 

 New Mexico during the season of 1894, though one of them had 

 previously been captured by Prof. Townsend. 



Mr. Fox, to whom I am very greatly indebted for comparing the 

 types with those of Cresson, has suggested the preparation of a 

 synoptic table. This, however, is deferred for the present, as it is 

 confidently expected that more new species will be found when they 

 are systematically looked for next year. 



The specific differences offered by these bees present a very in- 

 teresting problem to the Darwinian, and it is hoped to dwell at 

 some length on this phase of the subject hereafter. But attention 

 may be called to the peculiar and apparently constant (within nar- 

 row limits) markings of the face, which seem to fall under Wallace's 

 class of "recognition marks." 



All of the bees now described appear to me to be congeneric in 

 the strictest sense. It has not been thought necessary to mention in 

 each description those characters which run throughout the series ; 

 it is assumed that anyone using the descriptions has made himself 

 familiar with the generic type. 



With regard to the extent of the pale markings on the face, the 

 New Mexican species of Perdita form a series thus : — 



Semierocea -f phymatce -+■ sexmaculata, hyalina, albipennis, albovit- 

 tata, austini, canina, nitidella -+- foxi, martini, luteola. 



