CHAPTER XI 



nUMBLE-BBES AND OTHER MATTERS. 



Two liumble-bees, Bombus thoracicus and B. viola- 

 ceus, are found on the pampas ; tlie first, with a 

 primrose yellow thorax, and the extremity of the 

 abdomen bright rufons, slightly resembles the 

 English B. terrestris ; the rarer species, which is a 

 trifle smaller than the firsb, is of a uniform intense 

 black, the body having the appearance of velvet, the 

 wings being of a deep violaceous blue. 



A census of the humble-bees in any garden or 

 field always shows that the yellow bees outnumber 

 the black in the proportion of about seven to one ; 

 and I have also found their nests for many years 

 in the same proportion ; about seven nests of the 

 yellow to one nest of the black species. In habits 

 they are almost identical, and when two species so 

 closely allied are found inhabiting the same locality, 

 it is only reasonable to infer that one possesses 

 some advantage over the other, and that the least 

 favoured species will eventually disappear. In this 

 case, where one so greatly outnumbers the other, it 

 might be thought that the rarer species is dying 

 out, or that, on the contrary, it is a new-comer 

 destined to supplant the older more numerous 

 species. Yet, during the twenty years I have ob- 



