26 



XATl RAT. HISTORY 



very few cxcoplions, lias foiu* wings and six feet : as it performs, in this 

 connexion, a very important part in the organization, we examine it first. 



The Thorax, or chest, is formed of tliree segments perfectly united, 

 of which the anterior one, quite short and in the form of a collar, is the 

 prothorax ; the other two, or the mesothorax^ and ihe metathorax, are al- 

 wayi; fastened together, and seem to form but one whole. The latter is 

 terminated above by a small triangular piece, the vertex of which i.« 

 turned towards the head, and which is the scxdcllum. The upper part 

 of the thorax is called the lack^ and the lower the hreasf. The former 

 is almost always covered by the pterygoda, which, according as they 

 are more or less developed, alter the form of the thorax more or less. 



This form, although varying considerably according to the species, 

 is in general oval. According to the size, proportionate diiferences are 

 observed in the thorax. 



The HEAD is generally rounded, compressed in front, rather broader 

 than it is long, always a litde narrower than the thorax. Its anterior 

 part, or front, is called by most etymologists, though improperly, the 

 hood (chaperon). The head is very salient in the diurnals, and orna- 

 mented with fine hair. That of the Heterocerata is not so large, less 

 salient, ornamented with scaly hairs, and sometimes entirely drawn back 

 beneath the thorax, as in the .Rdclocephala. In some species it is dotted 

 like the prothorax. The important organs of which that part is the seat 

 are tlie eyes, the slemmata, the antennae, the paJpi, and the spirilrompe. 



The eyes, composed of innumerable little facets, are large, edged 

 with hairs, which probably fulfil the functions of eyelashes, and present 

 no peculiarity except in regard to the color which frequently changes 

 during life : in some species, as the Eurybia, they are of a brilliant 

 green ; brown as in the Sphinx and most of the Nocturna : reddish in 

 most of the Salyridae, etc. 



The stemmata, or eyelets, are situated upon the vertex, and do not 

 occur in all species : they are concealed under the scales, and are not 

 visible until the upper part of the head has been denuded. They are 

 to be seen, though not without some difficulty, in the Zygaenac, the 

 Frocrides, the Sesiae and most of the Heterocerata. 



The antennae, situated near the inner edge of each eye, are ordina- 

 rily shorter than the trunk, and composed of a great number of articu- 

 lations. Tiieir form is very variable : in all the Diurna, which for that 

 reason have been named Rhopalocerata, * they are filiform until near 

 the extremity, and terminated by a knob or club more or less elongated. 

 * f «7ri:4Ao» = club: ;c£j«{ = horn, antenna; that is, antennae terminated 

 willi a club. 



