12 THE THORAX. 



The thorax is generally considered to consist, as in 

 other insects, of three divisions — the prothorax, meso- 

 thorax, and metathorax. I have elsewhere, however, 

 given reasons into which I will not at this moment 

 enter, for considering that the first abdominal segmenL 

 has in this group coalesced with the thorax. The 

 thorax bears three pairs of legs, consisting of a coxa, 

 trochanter, femur, tibia and tarsus, the latter composed 

 of five segments and terminating in a pair of strong 

 claws. 



In the males and females the meso- and meta- 

 thorax each bear a pair of wings, which, however, are 

 stripped off by the insects themselves soon after the 

 marriage flight. 



The workers never possess wings, nor do they show 

 even a rudimentary representative of these organs. 

 Dr. Dewitz has pointed out that the full-grown larvse 

 of the workers possess well-developed ^ imaginal disks,' 

 like those which, in the males and females, develope 

 into the wings. These disks, dm-ing the pupal life, 

 gradually become atrophied, until in the perfect insects 

 they are represented only by two strongly chitiaised 

 points lying under the large middle thoracic stigmas. 

 No one unacquainted with the original history of 

 these points would ever suspect them to be the rudi- 

 mentary remnants of ancestral wings.' 



The thorax also bears three pairs of spiracles, or 

 breathing holes. 



• Zeit.f. miss. Zool., vol. xxviii. p. 665 



