54 



THE ANATOMY OF THE HONEY BEE. 



constitute the thorax of all other insects, but also of the first ab- 

 dominal segment. The conspicuous necklike constriction posterior to 

 the base of the hind legs (fig. 21, Pd) is, therefore, between the first 

 and the second abdominal segments (fig. 1, IT and I IT). 



The thorax of the honey bee at first sight looks entirely different 

 in structure from that of all other insects except related Hymenoptera, 

 in the higher families of which group it is more highly modified than 

 in any other order of the whole series of insects. When, however, we 

 examine the thorax of one of the lowest members of the Hymenop- 

 tera, such as a sawfly, we are surprised to find that, in each segment, 

 the structure agrees very closely with our ideal diagram of a general- 



ized thoracic 

 la segment (fig. 4). 



I :^ 1 ^Jg The three seg- 



■2 ,, — ,c„r -' ments are per- 



fectly distinct, 

 and the first 

 abdominal seg- 

 ment, while it 

 may be clearly 

 separated from 

 the rest of the 

 abdomen, is not 

 fused into the 

 thorax so as to 

 appear to be a 

 part of it. If, 

 now, we exam- 

 ine representa- 

 tives of several 

 families inter- 

 mediate between 

 the sawflies and 



the bees, the line of specialization that has produced the bee thorax 

 becomes perfectly evident. The principal features in these modifi- 

 cations are the following: 



(1) The lateral and ventral parts of the prothorax (figs. 20 and 21, 

 EpSi and S-^) are suspended loosely in a large membranous area 

 which is continuous anteriorly as the neck. They thus form a sort 

 of suspensorium for the front legs, which appears detached from the 

 rest of the thorax. (2) The protergum {T^) is solidly attached to 

 the anterior edge of the mesothorax and its lateral parts extend 

 downward till they meet on the venter behind the prosternum (figs. 

 20 and 21). (3) The postnotum (postscutellum) of the mesothorax 

 (figs. 22, PN ; 23 A, PN^) is entirely invaginated into the cavity of 

 the thorax and is reduced to the form of two lateral arms of the large 



Fig. 21. — Thorax of worker, left side, with intersegmental lines 

 somewhat exaggerated, showing prothorax (Ti, EpSi, Cxi), 

 mesothorax (T2, Eps^, Epnis, S^, Cx-z) , metathorax (T^, Ph, 

 ph, Oxs) and propodeum or first abdominal segment (IT). 



