88 BEES AND WASPS [CH. 



this respect it is to be observed that the humble-bees 

 resemble the social- wasps more nearly than they do 

 the honey-bee. Colour, unfortunately, is no sure 

 guide in distinguishing one species from another ; for 

 the colours of the hairs vary so greatly in different 

 individuals of some species that structural features 

 alone are to be trusted in diagnosis ; and these last 

 are often obscure and difficult to appreciate. How- 

 ever, the large black humble-bee with a red "tail" 

 will generally prove to be a "queen," Bomlms lapida- 

 rius', that with a yellow band across the thorax, 

 another near the front of the abdomen, and with a 

 greyish-tawny " tail," B. tcrrestris ; that of a tawny 

 yellow colour all over, B. venustus Smith (muscorum 

 Kirby), while that with a tawny thorax and black, or 

 black and tawny abdomen, B. agrorwn Fab (mus- 

 corum Smith). Meanwhile, it should be stated that 

 if the insect has smoky black wings, then it is not an 

 industrious Bomb us, but a lazy "cuckoo," Psithyrus, 

 of which there are several species closely resembling 

 the more virtuous Bombi on whom they foist their 

 young. 



According to their nesting habits the Bombi are 

 divisible into two groups : (i) those which nest beneath 

 and (ii) those which nest on the surface of the ground 

 "carder bees." B. lapidarius and terrestris are 

 examples of the former; B. venustus and agrorum 

 of the latter group. The underground species form 



