288 THE ZOOLOGIST. 



of the current induced by the contact of the two metals inside the 

 insect's body was measured by means of a galvanometer ; the 

 changes in strength of the current indicated the changes of heat 

 in the insect's body. 



The book begins with an historical review of the work of 

 naturalists on this subject since the time of Reaumur in 1734 ; 

 among other names we notice that of the English naturalist 

 Newport. The conclusion to be drawn from this earlier work is 

 that very different results may be obtained from working at the 

 same material ; that the temperature may vary within wide 

 bounds without prejudice to life, and that this variation of 

 temperature is largely dependent on the temperature of the sur- 

 rounding medium. But the temperature of the surrounding 

 medium is not the only factor in determining the temperature of 

 insects, and it is the first merit of Prof. Bachmetjew's work to 

 have fixed and defined the other important factors which co- 

 operate with it. He separates these factors under four heads — 

 1, the influence of the temperature of the surrounding air; 2, 

 influence of moisture ; 3, influence of exercise ; and 4, the in- 

 fluence of food and respiration. 



The first experiments described were made with the Hawk- 

 Moth (Deilephila euphorbia). It was found that at temperatures 

 higher than 37° C. the temperature of the moth was always lower 

 than that of the air, the greatest difference being 2*5°, when the 

 moth was at 45'1° C. Above 48*1° the insect ceased to flutter, at 

 48'6° its wings sank, and at 51*4° it died. At death the tempera- 

 tures of the air and of the moth were equal. These experiments 

 were conducted in air of normal moisture, but when the air was 

 supplied with additional vapour a different result was observed, 

 for then the insect had a higher temperature than that of the air, 

 and its wings did not sink until a body-temperature of 53° was 

 reached, the air being at 49°. This effect is probably brought 

 about by the moisture in the air preventing evaporation of the 

 insect's juices, and so preventing cooling; while the normal 

 metabolism of the insect naturally tends to raise the temperature. 

 At low temperatures the temperature of the insect was always 

 higher than that of the air. It is interesting to note, in rela- 

 tion to the effect of evaporation, that hairy insects tend to 

 have a higher temperature than smooth, and this fact may 



