SWALLOW-TAIL. 



151 



the 14th of Juno, 1841, and ten more in the 

 course of a fortnight. One died in the chry- 

 salis state, and one continued in that state 

 until this day, the 10th of May, 1842, when 

 a very fine and perfect female made her 

 appearance. I tried very much to continue 

 the brood, but was unsuccessful." 



The full-fed caterpillar ascends the reed 

 stems, generally so abundant in its natural 

 haunts, and often remains stationaiy in a per- 

 fectly straight position. The head is narrower 

 than the second segment, and very decidedly 

 narrower than the following segments : its 

 position is prone, and it is slightly notched on 

 the crown : the body is stout and cylindrical, 

 but has the divisions of the segments strongly 

 mai'ked; the second segment has a transverse 

 dorsal slit, from which the caterpillar can 

 protrude at pleasure, but more particularly 

 when annoyed a yellowish divaricating pro- 

 cess with the use of which I am quite un- 

 acquainted, and will therefore copy a few 

 lines from that inexhaustible storehouse of 

 entomological information, the " Introduction 

 toEntomology," by Messrs. Kirby and Spence. 

 These learned authors introduce the subject in 

 this way : " I shall next beg your attention 

 to those insects that emit their smell from 

 particular organs. Of these, some are fur- 

 nished with a kind of scent-vessel, which I 

 shall call osmateria, while in others it issues 

 from the intestines at the ordinary passage. 

 In the former instance the organ is usually 

 retractile within the body, being only exserted 

 when it is used : it is generally a bifid vessel, 

 something in the shape of the letter Y. . . . A 

 similar organ, hulf-an-inch in length and of the 

 ?ame shape, issues from the neck of the cater- 

 pillar of the Swallow-tail butterfly. ' When 

 I pressed this caterpillar,' says Bonnet, ' near 

 its anterior part, it darted forth its horn as if 

 it meant to prick me with it, directing it 

 towards my fingers, but it withdrew it as soon 

 as I left off pressing it;' this horn smells 

 strongly of fennel, and probably is employed 

 by the insect, by means of its powerful scent, 

 to drive away the flies and ichneumons that 

 annoy it," vol. ii., p. 242. And again : " In 

 a former letter I gave you a short account of 



the remarkable Y-shaped, as it should seem, 

 scent organ of the beautiful caterpillar of the 

 Swallow-tail butterfly: I will now speak of 

 it more fully. It is situated at the anterior 

 margin at the back of the second segment, 

 close to the head, from which, at first view, it 

 seems to proceed. At the bottom it is simple, 

 but divides towards the middle, like the lefr- 

 ter Y, into two forks of a fleshy substance, 

 which it can lengthen, as a snail does its 

 horns, to five times their ordinary extent, or 

 retract them within the stalk so as wholly to 

 conceal them. Sometimes it protrudes one 

 fork, keeping the other retracted ; and often 

 withdraws the whole apparatus for hours 

 together under the skin, and its place is only 

 marked by two tawny-coloured dots, so that 

 an ordinary spectator would not suspect the 

 existence of such an instrument," vol. iii., 

 p. 149. Dr. Horsfield, in his "Catalogue of 

 Lepidoptera in the Museum of the East India 

 Society," represents the caterpillar of Papilio 

 Xuthus with a similar appendage ; indeed, it 

 is extremely probable that many of the beau- 

 tiful insects which now constitute that strange 

 assemblage known as the genus Papilio may 

 be found to possess it. 



The surface of the skin is velvety, but every 

 parts emits very short stiff bristles, which are 

 only rendered conspicuous by means of a lens, 

 and then will be found to abound on the head 

 and on the twelfth and thirteenth segments. 

 The colour of the head is yellowish green, with 

 a black spot above the mouth, two longitudinal 

 black stripes down each cheek, and an oblong 

 black spot between them, which includes the 

 ocelli; there is a similar oblong black spot 

 immediately above the mouth. The ground 

 colour of the body is a most delicate and 

 lovely green : the second segment has three 

 oblong black spots immediately behind the 

 head and in front of the scent organ already 

 described; the interstices between the seg- 

 ments are velvety black and unspotted, form- 

 ing twelve transverse bars, and alternating 

 with these are as many velvety transverse 

 black bars, each being interrupted by six 

 bright orange spots, except on the second 

 segment, which has the black band unspotted 



