larva of Lycaena arion does during its last instar. 293 



elsewhere the larva was too opaque to show whether there 

 was anything of food material in its interior. 



The larva was found near the surface, but precisely 

 where in relation to the ants was not ascertained, the 

 earth being broken up before the larva was seen ; but it 

 was certainly not in any permanent tunnel or chamber of 

 the ants' nest, but more probably amongst the looser 

 surface material, brought up by the ants and not yet 

 consolidated, and amongst which, in weakly constructed 

 chambers, the ants dispose of their larvae temporarily on 

 fine warm days. 



The ant with which this larva was associated was 

 Myrmica scabrinodis var. sabuleti, for which name I am 

 indebted to Mr. Donisthorpe, who gives me, also, the 

 following names as those of the ants I sent him of species 

 which were more or less frequent or common in the locality. 

 Donisthorpea (Lasius) aliena, D. flava, Tetramorium caespi- 

 tuni and Myrmica scabrinodis. Whether L. arion larva 

 occurs with some or all of these also, remains to be seen. 

 D. flava has always been supposed to be its host, if it had 

 an ant host, and this is very probably correct, though the 

 grounds for the belief are that the thyme on which the 

 butterflies lay is often that growing on the hills of D. flava, 

 and that the larvae and pupae found by Mr. Frohawk were 

 apparently close to or on such a hillock. Nevertheless, 

 these ants are so numerous and their nests so close to 

 each other and almost, one might say, mixed together, 

 that, unless found actually living with the ants, and not 

 merely on or near their nests, one cannot feel at all sure 

 whether their supposed host is really one. On the other 

 hand, D. flava makes chambers and galleries, that look 

 very suitable for L. arion to inhabit, more extensive, 

 definite and formal than any of the other ants noticed, 

 and yet I and others have dug up and closely examined 

 dozens of nests of D. flava, without meeting with any 

 larva of L. arion in the actual nest. 



The hope of discovering what the larva would eat was 

 unavailing in view of the injury to the larva; there re- 

 mained, however, the possibility of learning what it had 

 eaten by examining the contents of the alimentary canal. 

 This, fortunately, proved to be a very satisfactory line of 

 investigation, and enabled its recent history, as regards 

 its food material, to be easily determined. 



The dark mass seen through the lower surface was the 



