OBSERVATIONS ON BUMBLEBEES. 73 



second when the latter was struggling to leave its cocoon. From 

 this rather superficial experiment, Wagner (p. 108) infers that 

 bumblebees do not assist their young during the process of 

 hatching. However, against this negative evidence of Wagner 

 (1907), we have the further positive evidence of Sladen (1912), 

 Bachmann (1915), and Prison (1917), whose observations I have 

 been able to confirm. 



XIV. THE ADOPTION OF INDIVIDUALS FROM OTHER COLONIES 

 Wagner (1907, p. 172) claims that after a bumblebee has been 



in the nest of another species from 10 to 12 hours she is, without 

 exception, treated as a member of the colony. This statement, 

 as well as Wagner's (p. 172) assertion that the specific odor of a 

 bumblebee colony emanates only from the queen, is disproved by 

 the results of several breeding experiments which I carried out 

 during the summer of 1922 (cf. 19230). These experiments show 

 that in some cases even members of such closely related species as 

 Bremus fervidus and Bremus pennsylvanicus may refuse to have 

 anything to do with each other, even after they have been to- 

 gether for weeks, and although the members of one of these 

 species have been reared by the other. 



XV. THE HOMING INSTINCT OF QUEENS AND WORKERS. 

 Wagner (1907) states that young bumblebee queens take a 



much longer orientation flight than the workers, and that despite 

 this fact they have much more difficulty in finding the nest than 

 the latter. I have observed the first orientation flight of a 

 large number of young queens and workers belonging to several 

 species, and although I found considerable individual variation 

 in the aptitude which these bees showed in finding the nest, I 

 failed to note any such correlation as that described by Wagner 

 (pp. 218-219). In fact, if any generalizations can be made, I 

 should say that the young queens appeared to have less difficulty 

 in finding the nest than the workers. 



XVI. NATURAL REQUEENING. 



In the works of Hoffer (1882/83), Handlirsch (i888a, i888b, 

 1891), Sharp (1899), Friese and Wagner (1904, 1910, 1912, 1914), 

 Vogt (1909, 1911), and Franklin (1912/13), one occasionally 



