Effects of certain Agents on Insects. 197 



became quite torpid, so that when roughly moved it showed no 

 signs of life. It was exposed to a temperature of 22°, without 

 fatal effect. 



A small fly (Piophila casei), pretty active in a window at 44° on 

 the 1 9th December, did not become torpid at 38°, moving its legs 

 when touched, nor at 33°: but at 31° torpor was produced, and 

 it bore without fatal effect a reduction of temperature to 22°. 

 After this it was active at 36°, and flew away when let into the 

 open air in the shade. 



On the 23rd February exposed a fly (Anthomyia mitts) to a 

 night temperature of 25° (the lowest) ; the following morning at 

 9 a.m. it was languid at 26°, moving its legs sluggishly when 

 touched. On the following night it was again exposed to a tem- 

 perature of 22°. When taken out of the tube, which was covered 

 with hoar frost, it was motionless for several seconds ; but in a 

 minute or two it moved its legs when touched, and, brought into 

 a warm room, it soon became active. 



A honey bee {Apis mef/ijica), active in the open air in sunshine 

 on the 9th March, became motionless at 40° in the shade. In a 

 room at 55° it moved its legs and wings languidly ; some hours 

 later at night, at 51°, it was found torpid ; breathed on, a languid 

 movement of its wings was reproduced ; placed where the tem- 

 perature was 65° it presently became active. The following 

 morning at 50° it was found motionless ; breathed on, on the warm 

 hand, a feeble revival was indicated by a slight motion of one of 

 its antennae, and occasionally of one of its legs: in this state, as 

 it were between life and death, it continued during five days, at a 

 temperature between 50° and G0°, at the end of which it ceased 

 to give any sign of vitality, the same means being employed to 

 excite it. 



These are all the trials I have made on the influence of reduc- 

 tion of temperature : they are smaller in number than I could 

 have wished, owing to the want of opportunities from the extreme 

 mildness of the season, as already adverted to ; and even in the 

 few instances in which the reduction of temperature was below 

 the freezing point it may be worthy of remark, that it was owing 

 not so much to the coldness of the atmosphere as to that of the 

 surface, the effect of radiation from the grass plat on which the 

 insects were placed during clear and calm nights, of which for 

 the time of the year there were unusually few. 



On the effect of elevation of temperature, to which I shall now 

 proceed, I have also a few results to describe. 



On the 19th January exposed a fly (Anthomyia mitis) in a tube 



