OF PAPILIONACEOUS INSECTS. 51 
periments of John Hunter and Spallanzani on this 
interesting subject. Indeed, the heat also which they 
are capable of withstanding, is not less astonishing. 
“«* Intense cold,” says Spallanzani, “ does not 
destroy the eggs of insects. The year 1709 was 
celebrated for the intensity of its cold, and its fatal 
effects on animals and plants. Fahrenheit’s ther- 
mometer fell to 1°. * Who can believe,’ exclaims 
Boerhaave, ‘ that the severity of this winter did not 
destroy the eggs of insects, especially those exposed 
to its influence in open fields, on the bare earth, or 
on the exposed branches of trees! Yet the general 
warmth of spring having again tempered the air, 
these eggs were hatched, and as numerously as in the 
mildest winters.’ Since that time, there have been 
winters still more severe ; for in France, as well as 
in several other European states, in December 1788, 
the thermometer fell considerably beneath that of 
1709. 
 T subjected eggs of several insects to a more 
severe trial than in the winter of 1709. Among 
others were those of the Silkworm Moth, and the 
Elm Butterfly, (Vanessa polychloris,) which I 
enclosed in a glass vessel, and buried five hours in 
a mixture of the ice and rock salt, when the ther- 
mometer fell six degrees below zero ; notwithstand- 
ing which caterpillars were extruded from all the 
eggs, and exactly at the same time with those which 
had not been subjected to this experiment, In the 
