138 THE ENTOMOLOGIST. 
at a foot beneath the surface. But looking on from the mere 
existence (uninjured) of the larve through winter cold, to the 
conditions of summer vitality, when feeding, growth and change 
of form are in active progress, we can lay our hands at once on 
proof of circumstances of temperature cooler than suit the 
constitution of the grub, in some cases retarding the date, or 
interfering with the healthiness of its development. 
We greatly need to know, for practical purposes, what these 
temperatures are, for it does not seem at all admissible to apply 
a general rule. In the case of the much-vexed question of the 
Colorado Beetle, we have information (pages 2 and 3 of the 
‘Seventh Annual Report on the Insects of Missouri,’ by 
C. V. Riley) that the crop was entirely free from injury by these 
insects above the altitude of about eight thousand feet. The 
bodies and eggs, and recently hatched larve, were to be found, 
but dried and dead, “which is probably due to the very dry 
atmosphere in connection with cool nights.” With some 
noticeable lepidopterous and dipterous examples the rate and 
healthiness of development may be traced in parallel sequence 
with the amount of accommodation (so to call it) afforded 
according to their constitutions during the time of rapid larval 
growth, or pupation; but it is very difficult to proceed onwards 
as to what may happen to species not easily noticeable, from the 
transformations taking place under ground. We have a well- 
known instance, however, amongst the ants (easy to be observed 
in Formica rufa) of the undeveloped insects being constantly 
moved so as to secure them the greatest available amount of 
sun-warmth by day and ground-warmth by night; and though, 
perhaps, I should ask to be excused in taking up time and space 
in what may be mere conjecture, yet it seems not impossible that 
observations of temperature on the ground level, and also taken 
with earth thermometers at the depth of one foot, and of two feet, 
beneath the surface, might throw some light on the causes for 
the varying depth at which larvee of one species may occur (with 
consequently varying opportunities of mischief); on retardation 
of development, or the contrary ; and many other matters, which 
would be serviceable as well as interesting. 
In the case of the somewhat rare beetle, Clythra quadri- 
punctata (the parasite or inquiline in the nests of Formica rufa), 
and of the still rarer Rhipiphorus paradoxus (parasitic in the 
