260 PTILOTA : IMAGO EXTERNAL ANATOMY. 



their existence. Of their uses I shall speak more at large 

 in treating of the physiology of insects, when I shall state 

 my reasons for employing the terms antenna; and palpi, 

 which indicate no decided use, in preference to that of 

 feelers, which is, by many authors, assigned mdiscrhnin:iirly 

 to these two kinds of organs. I will, therefore, only ob- 

 serve, that much still remains to be done before we arrive at 

 a perfect knowledge of the structure of the various organs of 

 the mouth throughout the insect tribes. Savigny has effected 

 much in clearing away the obscurity in which the subject had 

 long remained ; but there is still an ample field for the em- 

 ployment of a steady eye and hand, in dissecting, and espe- 

 cially in delineating, the many modifications of form to which 

 the parts of the mouth have been so fully shown to be 

 subject. Until this have been done in the most careful 

 manner, it will not be easy to arrive at a true knowledge of 

 the mode in which these modifications of form are effected, 

 and which alone will enable us satisfactorily to trace the ana- 

 logies of the various parts throughout the various orders. 



B. The Thorax, or Seat of the Organs of Locomotion. 



This portion of the body lies between the head and the 

 abdomen, and supports the three pairs of legs, and the two 

 or four wings with which perfect insects are in almost rvi ry 

 case furnished. 



In the early efforts made by scientific entomologists to 

 determine the various parts of the body of insects, too much 

 attention was paid to an organ when it happened to be fully 

 developed, too little to the mode in which this developeim-nt 

 was effected. Thus it sometimes happened that the same 

 organ received various names, according to its extent of de- 

 velopement ; and it was not till a rigid attention was paid to 

 the various forms which the same part exhibited in its vari- 

 ous modifications, that a fixed nomenclature could possibly 



