78 Trans. Acad. Sct. of St. Lows 
although what they respond to is not real darkness, but 
only a less light condition. In the same way, I have seen 
roaches escape into crevices; when their bodies touched 
the crack they were satisfied, even though they were ex- 
posed to full view in the light; their condition of positive 
thigmotropism satisfied their feelings in the matter of 
protection from danger, and they did not venture deep 
into the crevice. Here, however, it seems that light and 
sight were factors that prevented me from picking them 
up, for when attempts were made they crawled deeper 
into the crevices, whereas in the dark shadow on the floor 
an attempt was seldom made to escape because the roach 
could not see my approach. 
Roaches are very sensitive to odors or air conditions. 
One may handle the jar without disturbing the inmates 
if the jar is covered, or one may even remove the glass 
cover and come very near to look in if the breath is 
deflected, but to breathe, even gently, down into a jar 
at once creates a panic among the roaches. This simple 
test shows them to be susceptible to odor or air vibra- 
tions more than to sight. 
Their coming out of hiding does not seem to be regu- 
lated entirely by the quietness of the place. On many 
occasions I have found, when a house had been closed 
for several hours, roaches were out to feed as early as 
8:30 or 9 o’clock; on other occasions they may be found 
out foraging when the room has been darkened only a 
few minutes, when the noises of the city have by no 
means subsided. On the other hand, during the night 
when everything is quiet and one expects them to be out 
in abundance, one may find few or none. It seems they 
feed as early in the evening as possible and then retire. 
