Ixxii PROCEEDINGS OF THE 



anglers' flies, arranged according to the times of their appearance. 

 It was interesting to find that the "gray drake" and "green drake" 

 were hut sexes of one species, and to be able to identify the species 

 of the "stone flies." 



Mr. Westwood showed some flies and their eggs, part of a cluster 

 of sixty or seventy found in a tuft of hawthorn, about twelve miles 

 from Derby, and sent to him by Mr. Spencer, who had remarked 

 that each fly seemed to remain as a protector over the eggs it had 

 deposited. They were identified as Atheryx Ibis. 



A letter to Mr, Westwood, from Colonel Hearsey, now in India, 

 was read, detailing, among other interesting matters, some ento- 

 mological observations that his constant occupation with military 

 duties had not hindered him from making. 



The following observations on the influence of slight changes 

 of temperature on butterflies, by John Davy, Esq., M.D., F.R.S., 

 &c., in a letter addressed to W. Spence, Esq., were read : — 



" Lesketh How, Ambleside, 

 June 16th, 1849. 



" My dear Sir, — It was from you I learnt that no exact ther- 

 mometrical observations had yet been published on the degrees of 

 temperature at which hybernating insects, or those having pro- 

 perties analogous, pass from a torpid to an active state, and 

 consequently, that a record of any such observations, made with 

 exactness, would not be devoid of interest. 



" The observations which I have hitherto made on this subject 

 have been chiefly confined to two species of butterfly, viz. Vanessa 

 Urticce and lo. These I shall briefly relate. 



" The first-named butterfly I found active within doors in a 

 window on the 18th of last March, when the weather was unsually 

 mild for the season. It was in untarnished beauty, as if fresli from its 

 puparium. It was placed in a thin glass vessel, and lightly covered 

 with paper, so as to prevent its flight, and yet allow of a sufficient 

 access of air. Thus confined, it was put into a dark cupboard, the 

 temperature of which, even when there was a fire in the room, 

 was below G0° Fahrenheit. It remained alive about a month, and 

 during that time it was observed almost daily, and occasionally 

 oftener, — two or three times in the same day, and its place 

 changed. The following are the only notes that were taken down, 

 showing the effects of changes of temperature, in rendering it ac- 

 tive from being torpid, and vice versa. 



" April 11th. — Since first taken it has been found torpid at 58°, 

 as if dead, showing no indications of life even when shaken ; at 

 64°, or thereabouts, it has become active, and that even when 



