806 Tin; butterflies of new England. 



caterpillars the spines occupy a certain fixed place, and by means of this fea- 

 ture, among others, wc define the genus. Here then young and old cat- 

 erpillars plainly differ from each other in generic features. The case of the 

 spin}' catcrj)illars is still more striking in the Heliconians, to judge from 

 the chano'cs in Agraulis vanlllae and Apostraphia charithonia. For here 

 the appearance of the new born caterpillar is entirely different from its 

 appearance after its first moidt. In the first stage the head is unarmed 

 and the body supports longitudinal rows of very large papillae, each bcar- 

 inc a long, slender, naked hair with a delicate, ovate, apical club ; there 

 are at least four longitudinal series of these hair-bearing papillae above 

 the prologs. After the very first change of skin the head is armed above 

 with a pair of stout spines nearly as long as itself, bristling with distant 

 thorns ; the papillae and peculiar hairs of the body have entirely disap- 

 peared and in their place are long, tupering spines as high as the body 

 itself, with a very slight basal enlargement and furnished along their whole 

 length with minute papillae supporting little needles. The position of 

 these spines is quite different from that of the papillae of the first stage 

 and as if to mark this more distinctly there are but three longitudinal 

 series above the prolegs. These differences become intensified in every 

 subsequent ecdysis. 



To a casual view the caterpillars of our blue butterflies, our coppers and 

 hair-streaks, appear quite naked ; they are, however, profusely covered 

 with microscopic hairs ; but the newly hatched caterpillars are provided 

 with long hairs sweeping backward behind their bodies, most of them 

 arranged in longitudinal series ; the hairs themselves, too, instead of being 

 simple, as in the adult, are covered with microscopic spicules. So, too, 

 they are furnished in this early stage with rows of chitinous annuli or lenti- 

 cles, wholly wanting in the adult. In our white and yellow butterflies, Pieri- 

 nae, the pests of the garden and the glory of the fields, the differences between 

 youth and old age are much the same as in the meadow butterflies first 

 mentioned. In a general way, the same may be said of the skippers, but 

 the appendages of the new-born caterpillar are always shaped like little 

 clubbed mushrooms, and under the microscope bear an odd resemblance 

 to a row of cabbages in a vegetable garden. The caterpillars of our 

 swallow-tails, at least of those common in New England, are always nearly 

 naked when full grown ; we may find a few scattered hairs by searching 

 with a lens, and here and there a minute tubercle, or a smooth and shining 

 lenticle ; in soms species the front part of the body is swollen and fur- 

 nished with striking eye-spots ; at birth, however, the body is always 

 cylindrical and supplied with several prominent series of bristle-bearing 

 tubercles, one tubercle to a segment in each row, and one row often more 

 conspicuous than the others. Sometimes the entire body bristles with 

 these appendages. 



