THE BUTTERFLIES 3045 



the base of the wing, forming what is called the discoidal cell, whence there branch 

 off to the edges a series of horizontal, almost parallel, slightly divergent, nervures. 

 On the position of these the identification of species is most securely based, though, 

 in order to examine them, the insect must be spoiled as a specimen. In the moths, 

 on the other hand, the discoidal cell is less conspicuous, though nervures branch off 

 divergently from the base of the wing in a somewhat similar manner to those of the 

 butterflies. One of the most remarkable features in the wings of the Heterocera, 

 as distinguished from those of the Rhopalocera, is the existence of the frenulum 

 and retinaculum, briefly referred to above as the hook-and-eye arrangement, with 

 which the fore- wing is locked with the hind- wing. As already said, the scales are 

 modified hairs, which take a more and more perfect scale-like form toward the 

 centre of the wing. They lie in regularly-arranged rows, overlapping each other, 

 attached by a short stalk to a small forea or pit in the membrane, to the number of 

 many hundreds of thousands on each insect. Of different shapes and sizes they are 

 themselves, owing to their exquisitely-sculptured surface, objects of extreme beauty. 

 And it is to these alone that butterflies and moths owe their manifold tints, from 

 the sombrest browns to the most resplendent metallic greens, golds, and purples. 



The third division of the body is composed of a series of nine rings 



or segments, sometimes, as in the case of many of the moths, tufted 

 along the dorsal line, and also at the extremity. The spiracles, through which the 

 air passes to the trachea.1 system, lie along the sides of the abdomen, while the 

 organs of reproduction are placed at the extremity in both sexes. 



Butterflies and moths very rarely occur in the fossil state, owing no 



doubt to the delicacy of their integuments. Species of both, however, 

 have been found in Tertiary deposits and some few in nodules of amber. The Ter- 

 tiary beds of the Florissant lake basin of Colorado have furnished seven species of 

 butterflies, a dozen of moths, and one caterpillar. Two specimens of hawk moths 

 are known, in one of which is well preserved the spirally-coiled proboscis. Gal- 

 leries of the leaf -mining Tineina have been preserved in leaves from the Chalk, while 

 other Lepidoptera, a few pearl moths, owl moths, goat moths, silk spinners, bur- 

 nets, and clearwings, together, with a few species of Vanessa and blues, have also 

 been recognized. 



THE BUTTERFLIES SUBORDER Rhopalocera 



As distinguished from the moths, the butterflies may be recognized as a gen- 

 eral rule by their antennae, which, as suggested by the name Rhopalocera, are 

 slender and abruptly clubbed at the extremity. In some cases, however, in the 

 family of the skippers, these organs are gradually enlarged toward the tip, which 

 is itself often slightly hooked. Butterflies have not, in any case the hook-and-eye 

 arrangement the retinaculum and frenulum by which the upper and under 

 wings are in the moths interlocked along their inner margins. The fore-legs are 

 not always well developed, and this is particularly noticeable in members of the male 

 sex, forming a reliable characteristic in the broad subdivision of the Rhopalocera 



