
404 THE AMERICAN NATURALIST. [Vor. XXXVI. 
eleven minutes. In this case the critical point is —9.4° C., and 
— 1.4? C. is the normal congealing point. This insect revived within 
an hour after the experiment, and laid eggs on the following day. 
From this Bachmetjew concludes that the mere congealing of the 
body fluids is not lethal. In a second experiment a moth of the same 
species showed a critical point of — 11.6? C. (4.25 P.M.), whereupon 
the temperature rose at once to — r.1? C. The insect was kept in 
the cold, the temperature of its body again sinking to — 15.67. At 
6.15 P.M. it was removed to the temperature of the room, but could 
not be revived. It follows that the insect dies if its body is still 
further cooled after the rebound (the limits being not necessarily 
higher than — 2.5? C. nor lower than — 15.6? C.), or, as a general rule, 
it may be stated that the insect dies if its temperature be again 
reduced to about the point from which it rebounded. Further exper- 
imentation on this interesting subject led to the following general 
conclusions here briefly transcribed. The extreme degrees of under- 
cooling of the fluids differ in different insects, and these extremes 
occur at nearly the same rate of cooling. The critical point, so far 
as its absolute minimum is concerned, is greater in pupæ than in 
imaginal moths and butterflies, whereas the maximum differs in pupe 
and imagines. Owing to lack of material, the behavior of the larve 
could not be determined. With respect to sex, the degree of under- 
cooling of the fluids in normal specimens is lower in the males than 
in the females. This is also the case after brief fasting; after pro- 
tracted fasting, however, the degree of undercooling is lower in the 
males, but finally becomes the same in both sexes. On the other 
hand, the normal congealing point of the fluids is lower in the females 
than in the males. After fasting, it is the same in both sexes ; but 
after protracted fasting, the relation is again reversed. Further 
investigation of this question showed that the insect juices have a 
lower critical point when the insect is fasting, but so far as its abso- 
lute magnitude is concerned, it diminishes on continued. starvation. 
Repetition of undercooling gave the following results: On freezing 
a second time strong Lepidoptera exhibit a much greater degree of 
undercooling than on the first freezing ; on being frozen a third time 
the fluids show almost no undercooling. This is also shown by weak 
Lepidoptera on the second cooling. Bachmetjew also studied the 
influence of the fluid coefficient on undercooling. If M be taken as 
the total weight of the living insect, and Pits weight after drying on 
a water bath for a long time at a temperature of 115° C., 4 — P 


