70 BEES OF GREAT BRITAIN. 



say where the line is to be drawn which separates them ; if the 

 colour of the scopa alone is to be considered a good specific 

 distinction, there will be no difficulty : but there are varieties 

 of varians having the abdomen coloured as in helvola, the fringe 

 on the ventral segments being white, whilst the scopa is fuscous 

 above and white beneath. The male described as that of varians 

 was taken in coitu ; it is extremely like that of helvola, but its 

 head above is not so quadrate, and its mandibles are subdentate. 

 The species is retained with some hesitation ; it is not rare in 

 the London district during April and May, and is widely dis- 

 tributed. 



22. Andrena atriceps. 



A. nigra, griseo-pubescens ; thorace rufescenti ; tibiis posticis 

 fulvis, scopa fulvo-aurea. 



Melitta atriceps, Kirby, Mon. Ap. Angl. ii. 114. 55 $ . 

 Melitta tibialis, Kirby, Mon. Ap. Angl. ii. 107. 52 $ . 

 Andrena tibialis, Smith, Zool. v. 1737. 19 <J ? . 



Female. Length 6-7i lines. Black; the clypeus and cheeks 

 clothed with cinereous pubescence ; at, and above the insertion 

 of the antennae it is slightly fulvous. Thorax clothed above 

 with rufo-fulvous pubescence, at the sides and beneath it is 

 griseous ; the tegulae rufo-piceous, the wings subhyaline, ha- 

 ving frequently a fulvous tinge ; their apical margins faintly 

 clouded ; the fringe on the femora and the floccus white ; the 

 posterior tibiae and the tarsi rufo-fulvous, the scopa bright ful- 

 vous. Abdomen subovate, the apical margins of the segments 

 depressed, shining, covered with a short griseous pubescence, 

 and having a fringe of the same colour on the apical margins 

 of the segments ; the apical fimbria fuscous ; beneath, the 

 margins are ciliated with white. B.M. 



Male. Length 5-6 lines. Black ; the face clothed with black 

 or dark brown pubescence, the cheeks have a long beard of 

 pale fulvous pubescence ; the antenna? nearly as long as the 

 thorax, the joints of the flagellum subarcuate, the thorax has 

 a rufo-fulvous pubescence ; the wings as in the other sex ; the 

 tarsi and the apex of the posterior tibiae rufo- testaceous. Ab- 

 domen ovate-lanceolate, shining, and thinly sprinkled with pale 

 fulvous pubescence, the segments having a thin fringe of the 

 same colour ; the apex fulvous. B.M. 



Var. a. The posterior tibiae rufous half their length, sometimes 

 almost entirely rufous. 



