4 THE ENTOMOLOGIST. 



segment of the abdomen, in the females, are nearly of the same 

 relative length to each other ; they are also of nearly the 

 same form in both species. The abflomen of C. rufescens is 

 very convex both above and beneath, much more so than in 

 C. umbrina ; the pubescence is of an ochraceous colour, the 

 face being densely covered ; the pubescence of C. umbrina is 

 hoary, and the face of the insect only thinly clothed; in 

 other particulars they also differ widely. C. rufescens is also 

 a considerably larger species, being usually in length about 

 six lines, C. umbrina never exceeding four and a half. Figure 

 1 is the profile of the apical segment of the female of C 

 rufescens ; figure 2 represents the fifth, and also the apical 

 ventral plate of the abdomen of the female ; figure 3 is that 

 of a rare variety in the form of the apical plate, it having a 

 distinct spine or tooth at the apex. Figure 4 shous the 

 apical abdominal segment of the male, the upper teeth being 

 slightly divergent; in C. innbrina they are straight. Another 

 distinguishing characteristic of the male of C. rufescens is, 

 that in the middle of the fourth ventral plate of the abdo- 

 men there is a distinct notch ; it is only to be readily seen 

 by the aid of a pocliet lens ; the apex of the abdomen must 

 be pointed towards the eye, when the notch will be distinctly 

 visible in the middle of the margin of the fourth plate. 



4. C. umbrina will be separated by attention to the pre- 

 ceding remarks ; the females of C. umbrina and of C. rufescens 

 are the only ones that have the apical plates of the abdomen of 

 nearly the same length. Figure 14 represents the form of the 

 two apical ventral plates in the female; 15 is the same in 

 profile, and 16 the apical segment of the male. 



In my work on ' The Bees of Great Britain,' I quoted 

 Coelioxys mandibularis as a probable variety of C. simplex : 

 at that time I only possessed a single example ; subsequently 

 I obtained it from Carlisle : my first specimen was from 

 Yorkshire. The male I do not know, and that sex was not 

 known either to Nylander or Bohemann, to both of whom I 

 showed ray unique British example. I am now quite dis- 

 posed to consider it a good species. The species named 

 "sponsa" in my work I suspected to be the male of C. 

 simplex, and since the publication of my book Mr, New- 

 combe, of Darlford, bred both sexes of C. simplex from a 

 nest of Megachile ligniseca, the male proving to be my 

 C. sponsa. 



