OBSERVATIONS ON BUMBLEBEES. 67 



leaving the center of the mesonotum completely bare. Similar 

 observations were made on several Bremus fervidus colonies 

 during the summer of 1922. Investigation showed that these 

 lumps of pollen were acquired by the bees while they were gather- 

 ing nectar from Linaria, popularly known as butter and eggs, 

 or toad flax. In the light of these facts, it is not surprising that 

 Schmiedeknecht's (pp. 384, 424) predictions in regard to the 

 nesting habits of some of the rarer European species have proved 

 to be incorrect (cf. Gundermann, 1908, p. 31). This is also true 

 of some of the predictions of Hoffer (cf. Harter, 1890, pp. 71-73). 



II. THE STRUCTURE OF THE OUTER NEST. 

 Wagner (1907) states that the fibrous envelope of epigeic 

 bumblebee nests is composed of two distinct layers which he 

 calls the outer and the inner nest. Although I have examined a 

 large number of epigeic nests belonging to several American and 

 European species, I have never found an indication of such an 

 arrangement, and this leads me to believe that such nests as 

 those shown by Wagner (pp. 31-32) in Figs. 14, 15, and 16, 

 instead of being of universal occurrence, are extremely rare. 



III. THE POPULATION OF A BUMBLEBEE COLONY AT NIGHT. 

 Packard (1865), Coville (1890), and Sladen (1912) state that 

 the whole population of a bumblebee colony is at home during 

 the night, while Shuckard (1866), whose observations agree with 

 those of Hoffer (1882/83), nas the following to say concerning 

 this matter : "If, in their collecting excursions, they are intercep- 

 ted by heavy rains, or loiter far away too long until twilight 

 closes, they will pass the night away from home, and return laden 

 with their gatherings as soon as the warmth of the sun reanimates 

 them to activity; thus they will often sleep in flowers, and a nest 

 therefore taken at night is not always a sure indication in those 

 found within it, of its complete population." For many years, 

 I also held the same opinion as Packard (p. 109), Coville (p. 198), 

 and Sladen (pp. 47, 99), but during the summer of 1921, I 

 accidentally discovered that the observations of Shuckard (p. 315) 

 and Hoffer (p. 5) are correct. 



