l8o THE BUTTERFLIES OF THE BRITISH ISLES. 



previous day ; they were placed upon thyme blossoms and soon 

 commenced to feed, one being observed to eat its way into the 

 base of the calyx so that the forepart of the caterpillar was 

 hidden. In its colouring and downy covering the caterpillar so 

 closely resembles the flower-buds of the thyme that it is very 

 difficult to detect. After the third moult (July 26) the colour 

 is a uniform, dull, ochreous-pink ; there are four rows of long 

 curved hairs, each row composed of a single hair on each ring 

 from the fourth to the ninth inclusive ; the first three rings have 

 each a set of three subdorsal hairs, those on the first ring curving 

 forwards ; the bases of the hairs resemble glass-like pedestals 

 with fluted sides. The head is ochreous with dark brown mark- 

 ings in front. The caterpillar at this stage develops an aversion 

 to thyme or any other plant offered to it, and seems to be anxious 

 to hide itself in the ground. 



The chrysalis, which is figured on Plate 116 (after Frohawk), 

 is ochreous when first formed, but becomes darker gradually ; 

 the wing-cases, however, remain of the original colour, but their 

 hind margins darken. From a chrysalis found on July 12 the 

 butterfly emerged on July 16. 



There is some evidence in favour of the supposition that 

 this caterpillar is in some way dependent upon ants for nourish- 

 ment after the third moult, if not before, but what the exact 

 requirement may be is not known. Probably the circum- 

 stances connected with the discovery of the chrysalis in 1905 

 by Messrs. Frohawk & Rayward may afford a valuable clue to 

 the direction in which their future investigation will have to be 

 conducted. We may hope, therefore, that the mystery that has 

 so long hung over the last stages of the caterpillar will be solved 

 before very long. 



Lewin (1795) and Donovan (1796) both refer to this as a 

 rare English butterfly. The former states that it is on the 

 wing in July, and is found on high chalky lands in different 

 parts of the kingdom, having been taken on the cliffs in the 



