134 GRAMMAR OF ENTOMOLOGY. 



originate precisely in the same manner as the 

 muscles in the human frame, are attached to, and 

 originate in, the bones. 



498. The bulk and form of muscles in insects 

 are beautifully apportioned to the offices they are 

 required to perform ; and unusual bulk in any 

 part of an insect generally implies the presence of 

 unusually developed muscle, and the object for 

 which it is developed maybe readily ascertained. 



499. We have before seen, that the fore wings 

 arise from the mesothorax, and the hind wings 

 from the metathorax : these segments vary greatly 

 in size, and this variation depends so precisely on 

 the powers of flight possessed by each pair of wings, 

 that an insect anatomist, on regarding these two 

 segments alone, would at once decide on the rela- 

 tive power of the wing which they had borne. 



500. In flies, the fore wings are alone used in 

 flight ; the hind wings are rudimental ; the whole 

 bulk of muscle, therefore, required for flight, is 

 placed in the mesothorax : in beetles the hind 

 wings are alone used in flight, and the bulk of 

 muscle is consequently transferred to the meta- 

 thorax. 



501. It happens in some moths, that one sex 

 flies and the other does not ; and in these the 

 structure of the wing-hearing segments at once 

 proves the provision of muscle in these is for the 

 purpose of flight. 



502. In the common ant the little worker never 



