30 THE BUTTERFLIES OF THE BRITISH ISLES. 



The caterpillar when full grown, as figured on Plate i, is 

 bright green with an orange-spotted black band on each ring 

 of the body, and blackish tinged with bluish between the 

 rings. The head is yellow striped with black. When it first 

 leaves the egg-shell, which it eats, the caterpillar is black 

 with a noticeable white patch about the middle of the body. 

 After the third change of skin it assumes the green colour, and 

 at the same time a remarkable V _sna P e d fleshy structure of 

 a pinkish or orange colour is developed. This is the 

 os?naterzum, and is said to emit a strong smell, which has 

 been compared to that of a decaying pine-apple. The organ, 

 which is extended in the figure of the full-grown caterpillar, 

 is not always in evidence, but when the caterpillar is annoyed 

 the forked arrangement makes its appearance from a fold in 

 the forepart of the ring nearest the head. Other food-plants 

 besides milk parsley are angelica {Angelica sylvestris), fennel 

 {Famicidum vulgare), wild carrot (Daucus carotd), etc. From 

 eggs laid in May or June caterpillars hatch in from ten to 

 twelve days, and these attain the chrysalis state in about six 

 or seven weeks. If the season is a favourable one, that is fine 

 and warm, some of the butterflies should appear in August, 

 the others remaining in the chrysalids until May or June 

 of the following year ; a few may even pass a second winter 

 in the chrysalis. Caterpillars from eggs laid by the August 

 females may be found in September, nearly or quite full grown, 

 and chrysalids from October onwards throughout the winter. 

 They are most frequently seen on the stems of reeds, but they 

 may also be found on stems or sprays of the food-plants, as 

 v/ell as on bits of stick, etc. It would, however, be practically 

 useless to search for the late chrysalids as the reeds are usually 

 cut down in October, when the fenmen keep a sharp look-out 

 for them, and few are likely to escape detection in any place 

 that would be accessible to the entomologist. 



On Plate i three forms of the chrysalis are shown. The 



