198 Dr. John Davy on the 



of thin glass to a temperature of 120° ; in two or three minutes it 

 became motionless and was found to be dead. The same effect, 

 in as short a time, was produced on another fly of the same kind 

 by a temperature of 113°. On the 28th January exposed another 

 also of the same kind to a temperature gradually rising (the tube 

 being immersed in water) to 96°. After about an hour the fly 

 that was at first active was found lying at the bottom of the tube, 

 seemingly incapable of standing ; in another minute it ceased to 

 move, and did not revive on exposure to the air of the room. 

 Another of the same kind bore well a temperature between 80° 

 and 90° for two hours ; after exposure to a temperature between 

 90° and 100° less than an hour, it was found dead. 



A fly (Musca lanio) on the 30th January was exposed to a tem- 

 perature between 80° and 90°, and 90° and 100°, for several hours ; 

 so long as the air in the tube was below 100° the fly did not appear 

 to suffer ; above 100°, it showed a tendency to become torpid ; at 

 105°, after a very few minutes, it became motionless, and did not 

 revive on exposure to the air of the room. 



On the 16th March, a honey bee, — just taken from the open air 

 at 45°, when in sunshine actively on the wing, — was exposed to a 

 gradually increasing temperature. Its activity was not apparently 

 diminished at 80° ; at 90° the sound of its wings had ceased : it 

 was at rest at the bottom of the tube, but in nowise torpid ; after 

 a few minutes, at 96°, it became motionless ; then taken out, and 

 exposed to the air of the room at 55°, it did not revive ; no part 

 of it afterwards moved. 



What is known of the habitats of insects in relation to climate, 

 I need hardly remark, amply proves the vast range of temperature 

 at which different species can exist, — each probably restricted to a 

 certain range, — and consequently that a very large number of trials 

 on different species would be required to arrive at any satisfactory 

 conclusion on the influence of temperature on insects generally. 

 One remark I beg to make, in which I think I am warranted by 

 my limited experience, — as to the effect of change of temperature, 

 — viz. that on insects it is different from what it is on the hyber- 

 nating mammalia ; not, as in them, producing a quick transition 

 from active to torpid life, but more commonly a graduated one 

 from great activity to diminished, till motion is altogether lost ; and 

 this gradation, whether in becoming torpid from cold, or in reco- 

 vering from a state of torpor on elevation of temperature. 



