GENERATIONS OR BROODS OF INSECTS. 
21 
"We have observed that certain species of insects and often individ- 
ual insects may without any assignable reason remain a considerably 
longer time than usual in the pupa state. Lyda stellata usually has a 
single brood (one year generation) while it frequently happens that 
from the pupa beginning the first of May, the imago does not fly at the 
end of May or in June, as is the rule, but that the pupa state lasts over 
to the next May, when the adult flies! The pupal rest in this case lasts, 
instead of three weeks, more than a year. A similar case is that of 
Cnethocampa pinivora. This relation is connected with the fact that 
insects are cold-blooded, or better, poikilothermic, i. e., changeably warm 
animals. We understand thereby such animals as those whose peculiar 
body heat, although constantly a little higher than that of the surround- 
ing medium, the air, water or earth, i. e., their habitat, yet varies with 
the changing temperature of this medium. In contrast with these are 
the warm-blooded, or, more exactly, the homceothermal. i. e., animals with 
an even temperature which as long as they live steadily maintain their 
own normal temperature up to a height ranging at most 1° O. The 
blood-heat of a healthy man, although he may be exposed to a degree 
of cold of — 30o C. or a warmth of + 30° C, remains steadily at 38° 0. 
( Judeich and Nitsche.)* 
The duration of development of a warm-blooded animal is definite. 
The development of an insect's eggs, however, is analogous to that of 
a fish. We best see this when at the beginning of spring the leafing 
out of the foliage is late and the caterpillars of Clisiocampa hatch cor- 
respondingly late. Exact series of observations of indubitable cer- 
tainty are scarcely at hand, but, add our authors,t we will cite the posi- 
tive statements of Regener| on the influence of temperature on the 
duration of development and of life of the pine Bombyx at different 
temperatures, though, indeed, they are somewhat inexact and incom- 
plete. 
Provisional tabular view of the life-history of the Pine spinner (Gaslropacha pini) at dif- 
ferent temperatures, after Begener. 
Temperature, 
°C. 
Duration (in days) of— 
Egg-stage, 
from laying 
to hatching. 
Caterpillar, 
from hatch- 
ing to spin- 
ning of 
cocoon. 
Spinning of 
cocoon. 
Prepara- 
tions for 
pupa. 
Pupal rest. 
+ 4° to 5° 
-t- 6° 
+ 9° to 11° 
+ 11° to 14° 
+ 15° to 19° 
+ 18° to 21° 
+ 20° to 24° 
+ 24° to 28° 
36 
26 
20 
18 
17 
16 
500 
196 
152 
119 
84 
67 
56 
15 
9 
24 
2 
3 
2* 
2 
k 
49 
36 
26 
21 
* Each degree of the Centigrade thermometer is equal to lg-° of Fahrenheit; and 
0° is at the freezing point of water. 
tJudeich and Nitsche, I, 116. 
X E. Regener. Erfahrungen iiher den Nahrungsverbrauch und liber die Lebens- 
weise, Lebensdauer und Vertilgung der grossen Kiefernraupe. Leipzig : Emil 
Baensch's Verlag. 1865. 
