S2 [^Pril, 



VARIATION IN BRITISH PSITHYRUS AND REMARKS 

 ON BOMBUS POMORUM. 



BV H. C. L. PEEKIXS, M.A., D.SC, F.R.S. 



The mai\y variations of our species of Bomhus and Psithyriis have 

 lieen insnfficiently studied, and their distribution especially is very imper- 

 fectly known. The cliief varieties of the latter genus are here mentioned, 

 and when it has seemed advisable I have made tables for their separation. 

 In many cases, no doubt, intermediate forms exist, and when more 

 special attention is given to their collection 1 expect numerous other 

 variations will be discovered. In cases where varieties were once 

 considered to be distinct species, and had names given to them, I have 

 added these names. As a rule the males are much more variable than 

 the females. If specimens of the former are dissected, this should be 

 done carefully so that the pubescence is not disordered, and on no 

 account should this be allowed to get wet. The external structural 

 characters are so good that dissection is never necessary, for doubtful 

 specimens are never met with in my experience. Variations caused by 

 patches of white or pale hairs, which are often irregular ur asymmetrical, 

 are not referred to. According to Sladen, they are generally due to 

 pathological conditions. 



P. caivpcstris Panz. 

 6 6. 

 1 (8) Thorax witli distinct yellow hand in front and frequently also 



yellow behind, or even yellow all over except on the disc. 

 '1 (3) The whole abdomen except the extreme tip with yellow hairs, 

 the sides of the thorax also clothed with yellow hairs, even 

 those on the propodeum mosily or entirely yellow 



. . . .var. « (Scotland). 



3 (2) Abdomen with at le.tst some black hairs, if only at the sides of the 



second sefinient amongst the yellow ones. 



4 (7) Basal abdominal segment with yellow clothing. 



5 (G) Clothing of the abdomen yellow, but with some black hairs at the 



sides only of the second segment var. /3 (Pjnpland). 



6 (5) Second segment altogether or largely black-haired, so that an entire 



black ba,nd is formed, the third often more or less black-haired 

 basally var. -y (rossiMns K.). 



7 (4) Basal abdominal segment as well as the second black haired 



. . . .var. 8 (leeanvs K.). 



8 (I) Thorax entirely black-haired or at most with faint indications of a 



band in front. 



9 (10) Basal abdominal segments black-haired, the apical ones notably pale, 



the hairs yellowish, subolivaceous or sometimes obscurely sub- 

 ferruginous var. ( > franciscimns K. ). 



