19 
been pastured. If a temporary drought occurs there 
is an unusually large breadth of land made available 
for egg-laying by the partial drying-up of the swamps, 
and there the caterpillar can thrive and turn to chry¬ 
salis ; but now, if wet returns and the swamps are 
unsuitable for the moths, they are driven out to infest 
the whole country. Whether this is really the case, 
and the cause of occasional bad attack, is a matter 
on which opinions differ, but any way the details give 
an example of how weather influence, changing with 
the changing needs of the insect, may increase its 
numbers. 
The conditions of temperature and air in high alti¬ 
tudes are found to have marked effect on the develop¬ 
ment of some insects. It is recorded by Professor 
Riley that whilst injury from the Colorado Beetle 
reached up the Alleghany Mountains to a certain height 
above sea-level, that above that altitude the crops did 
not suffer. Bodies and eggs were found, but the eggs 
or the larvae just hatched were dried up and dead, and 
it is considered that this destruction is owing to the dry¬ 
ness of the air joined to the cool nights. 
Some valuable observations taken by Mr. II. Pryer 
in Japan relatively to the difference in size and colour 
of butterflies, which occur in connection with differences 
of temperature, have recently been published by the 
Entomological Society.* These changes he states not 
to depend so much on the season of the appearance 
of the perfect insect as on the temperature that the 
larva has borne during its existence in this condition. 
The temperatures noted ran rather more to extremes 
than our own, as they are mentioned as frequently sink¬ 
ing as low as 22° or 20° in winter (or, as it is commonly 
said, to ten or twelve degrees of frost), and in summer 
frequently to rise to 88° or 90° in the shade. 
* “ On certain temperature forms of Japanese Butterflies,” by 
H. Pryer, C.M.Z.S., Trans, of Ent. Soc. of London for 1882, 
part iii., pp. 485—491. 
