148 STATES OF INSECTS. 



remarkable Y-shaped, as it should seem, scent-organs 

 (Osmateria) of the beautiful caterpillar of the swallow- 

 tailed butterfly (Papilio Machaon L.), and others of the 

 Equites a ; I will now speak of them more fully. That 

 found in the former is situated at the anterior margin at 

 the back of the first 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 let- 

 ter Y, into two forks, of a fleshy substance b , which it can 

 lengthen, as a snail does its horns, to five times their or- 

 dinary extent, or retract them within the stalk, so as wholly 

 to conceal them. Sometimes it protrudes one fork, keep- 

 ing 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 c . Unfortunately this larva is rare 

 in this country, so that I can scarcely flatter you with the 

 hope of seeing this curious organ in a living specimen d , 

 unless you choose to import a parcel of its eggs from the 

 south of Europe, where it is common. This you will 

 think rather a wild proposition ; but why should not En- 

 tomologists import the eggs of rare insects, as well as bo- 

 tanists the seeds of rare plants? But if you will be satis- 

 fied with the dissection of a dead specimen, I have seve- 



a See above, Vol. II. p. 244 — . 



b Plate XIX. Fig. 1. a. 



c Reaum. i. t. xxx./. 2. N. Diet. d'Hist. Nat. xxiv. 490, 497—. 



d Ray says he found it feeding on common fennel, about Middle- 

 ton in Yorkshire : Lett. 69. The indefatigable Mr. Dale recently 

 found many in the neighbourhood of Whittlesea-mere, feeding on 

 Selinum palustre. It will also eat the wild carrot. 



