^O NATURAL HISTORY 



to some authors, is the only one that serves for the transmission of nu- 

 tritive juices. When inactive it is always spirally rolled up between 

 the palpi. All the Rhopalocerata are provided with a well developed 

 spiritronipe. In the Heterocerata its length varies greatly. In some 

 Spldnges it is two or three times as long as the body ; very short in 

 many Geomeirae, and in a part of the Bonihyces it exists only in a rudi- 

 mentary form. 



Thk Abdomen is ovally elongated, or almost cylindrical in most 

 species. It is composed of seven rings, each of which, again, is formed 

 of a superior arc and of an inferior arc united together by a membrane. 

 The former are a great deal longer than the others, and sometimes cover 

 them with their edges in such a way that the abdomen below seems to 

 form a gutter. This arrangement gives it the power of dilating itself 

 considerably, as is to be seen in some females before laying. The or- 

 gans of reproduction, peculiar to each sex, are placed at its extremity. 

 The color of the abdomen, in most of the JVocluac^ resembles that of 

 the inferior wings. In the Clieloniae, the Glaucoins^ and many species 

 of Bombycidae, it is ornamented with colors not less brilliant than those 

 of the wings. 



The Wixgs attached to the superior lateral part of the thorax are 

 always four in number, except in some females, where they are either 

 entirely wanting or reduced to mere germs insufficient to enable them to 

 fly. Each wing, considered by itself, consists of two membranaceous 

 laminae intimately united together by their internal surface, and divided 

 into numerous distinct parts by horny threads which are more or less 

 prominent and called nervurcs. The two laminae, which constitute the 

 upper and the under side of the wing, are covered with a farinaceous 

 dust which is removed by the touch. With the aid of a microscope, 

 and sometimes even by the naked eye, it is seen that this dust is a col- 

 lection of small, colored scales, fastened into the membranous part by 

 means of a pedicle, and arranged with the same symmetry as the tiles 

 on a roof. Their form varies greatly according to the species, and even 

 in the same species they are greatly diversified according to the part of 

 the wing which they cover : they are generally much larger in the Hete- 

 rocerata than in the Rhopalocerata ; but no genus presents them more 

 distinct or larger than the Castnla, in which they may almost bear com- 

 parison with those of certain fish. The colors, so various and so beau- 

 tiful, presented by the wings of Lepidoptera, are due, not to the mem- 

 brane, which is always transparent, but to the scales. No Lepidopter 

 is destitute of scales ; but in some they are so small and so few in num- 

 ber, that the wings arc perfectly transparent, as in many Satyridae, etc. — 



