402 THE AMERICAN NATURALIST. [Vol. XXXVI. 



that of the atmosphere, and only begins to approach atmospheric 

 temperature just before partial heat paralysis of the wing muscles 

 sets in. After death the temperature of the insect and the air are 

 the same. But when the air is very damp the body temperature of 

 the insect is higher than that of the air. This is explained as due to 

 evaporation of the body fluids and to respiration, the former having 

 a tendency to diminish, the latter to raise, the temperature of the 

 insect. Bachmetjew predicts that the study of the dependence of the 

 body temperature on that of the air, under different conditions of 

 moisture, will ultimately enable us to determine the metabolism of 

 these animals, and hence their vitality at different temperatures. 



The influence of the activity of the insect on its body temperature, 

 long since noted by Newport (1837) and others, is exhaustively 

 studied by Bachmetjew. While a moth is moving its wings its body 

 temperature keeps rising, but falls suddenly with the cessation of this 

 movement. The insect was studied under three conditions : first, at 

 the ordinary temperature of the room ; second, at a higher tempera- 

 ture in the thermostat ; third, at a lower temperature in a cold-air 

 bath. Experiments conducted at room temperature show that the moth 

 (Sphingid) is incapable of raising its own temperature higher than 

 38.5° C. by means of muscular movement. Fluttering of the wings 

 does not produce as high a temperature as " humming." At about 

 38° C. the insect often suddenly changed from humming to fluttering, 

 or rested completely. Bachmetjew interprets this change as due to 

 partial heat paralysis of the muscles. It is a transitory phenomenon, 

 which disappears with the sinking of the temperature during rest to 

 that of the surrounding atmosphere. The temperature at which the 

 wing muscles are paralyzed (in Deilephila eiiphorbicc) increases with 

 an increase of the temperature (at ordinary moisture) and reaches 

 45.5° C, after which the moth loses the power of humming. Com- 

 plete, i.e., no longer transitory, heat paralysis of these muscles super- 

 venes at a body temperature of 49.7° C. In somewhat moister air 

 this result does not set in till 53° C. is reached. In a single experi- 

 ment on Deilephila at low atmospheric temperature the muscle 

 paralysis also appeared, but at a lower temperature. At a body tem- 

 perature of — 0.5° C. all movements ceased, fluttering began at 12° C, 

 and humming not till 20° C. had been reached. It would seem, 

 therefore, that the temperature of partial paralysis of the wing mus- 

 cles is directly proportional to the body temperature of the insect, as 

 is also the case for higher temperatures. According to Bachmetjew, 

 these effects of partial paralysis play a great role in the production 



