Sept. 1897.] Packard: Transformations of Hymenoptera. 115 



Of the first brood of males and females the latter were not neaily so 

 dark and hairy as the males, which were just ready to leave their cells, 

 except one which was a subimago. 



I first observed this dimorphism in the pupae taken from this nest ; 

 it was better seen than in examining the adult bees. 



The eggs are elongated cylindrical, with the ends truncated and 

 rounded off; and they are slightly curved in themselves. 



Larva of Worker. — In their general form the larvae of Bombus agree 

 closely with those of Apis and Megachile. In outline lunoid the body 

 is thick, cylindrical, though a little flattened, and the rings rapidly 

 diminish in width towards each end of the body. In their natural atti- 

 tude the larvse when in their cells are doubled upon themselves, so that 

 the under side of the head is closely oppressed to the tip of the abdo- 

 men. The enlarged pleural surface, which forms a raised lateral ridge, 

 aids in giving the flattened appearance to the body. On the hinder 

 half of each ring of the body is a tergal raised, flattened band proceed- 

 ing on each side from the lateral ridge, leaving a transverse depressed 

 ovate lanceolate area, at each end of which is a spiracle. There are ten 

 spiracles, one for each thoracic ring and one on each of the first seven 

 abdominal rings. 



Beneath the body is flattened, and the sternal region is very distinct 

 from the raised pleurae. Each ring has its surface raised into two trans- 

 verse ridges. 



Above, the thoracic rings differ from the abdominal ones in having 

 the raised portions cover nearly the whole surface, which actually takes 

 place in the prothoracic ring. It is on this raised portion that the 

 minute horny acute papillae are situated ; two for each second and third 

 ring, and three on the middle of the prothoracic ring in a transverse 

 line. The arrangement of these tubercles does not essentially vary in 

 the different species. The prothoracic ring is a third narrower than in 

 the metathoracic ring, though as long. The tenth and abdominal ring 

 is in outline equal in size to that of the head, being orbicular when seen 

 from behind. Its surface is marked below by an oblong square raised 

 mesial portion, twice as long as broad. There is no anal outlet since the 

 intestine is a blind sac. The 9 and ^ genitals can be distinctly seen, 

 so that the sexes of the larvae can be easily distinguished. 



Of the two pairs of stylets on the ninth ring, the most basal and outer 

 are triangular, and the inner sides nearly meet over the mesial line of 

 the body. The smaller outer and more remote pair have their greatest 

 length across the ring ; their tips nearly meet on the mesial line of the 



