400 HOUSE FLIES, TORPOR OF. 
highly curious and pleasing. When a fire has been 
lighted in my bed room I have always found that 
this artificial heat calls flies out even during the 
severest weather, and when, as often happens, a few 
warm days occur at Christmas, they are also re- 
suscitated, though in fewer numbers, and seemingly 
in possession of less vigour. March seems to be the 
first period of the emergence of flies and other dor- 
mant insects ; on March 7th, 1838, I found a beetle 
just issuing forth, but this happened to be an un- 
usually warm day ; the generality in my opinion are 
not revived till warm days in April, and even then 
are susceptible of semi-torpidity on the intervention 
of cold inclement days ; on April 10th, 1838 which 
was a cold day, a fire in: my bed room called forth 
many flies, and none were to be seen in other rooms 
without fire, or out of doors. On April 11th I re- 
marked a kind of bee in a semi-torpid state in a hole 
ofa wall, so that it is with insects as with reptiles, 
temperature is the grand agent on their constitu- 
tions, and sets in action those instincts which pro- 
mote their welfare at this juncture in their lives. 
Bats appear abroad during every month of the 
year, and in winter principally select fine and warm 
evenings, though I have also noticed them on keen 
frosty nights ; once particularly, I remember seeing 
one crawling or running on the snow during a very 
cold night, January, 19th, 1838; I attempted to 
seize it, and it eluded me with great dexterity and 
finally escaped into the hedge. I should suppose 
however that this anomalous kind of reviviscence 
is attributable, as Mr. Rennie remarks, to that wise 
ordination of Nature which causes great cold to 
revive some torpid creatures and thus saves them 
from becoming its victims. Query—Does the de- 
pending posture of the head in torpid bats, contribute 
to their lethargic state. 
