The Biology of the Roach 77 
hold itself together for many days, and is very notice- 
able on the black backs of the roaches. Just exactly 
where it comes from or what its function is, I do not 
know, but it probably oozes out from pores in thin chitin 
at the joints of segments and probably functions in some 
way in the mating or reproductive processes. This ma- 
terial was never seen to gather on the bodies of the males 
or on the mated females, but only on the virgin females. 
It is not wholly accurate to say that the mated females 
never showed this secretion; I should say, rather, that 
this material did not appear on the bodies of hundreds 
of females caged together with males, but at the same 
time in a group of virgin females that were segregated, 
almost all of them had varying amounts of this slime 
that exuded from the dorsal folds of the last few 
segments. 
Miscellaneous activities—Roaches are negatively 
phototactic and positively thigmotactic. Writers gen- 
erally agree that roaches are gregarious, but it seems 
to me that their gregariousness has more or less been 
thrust upon them; being negatively phototactic and posi- 
tively thigmotactic, and with large numbers of them seek- 
ing the same environment in limited space and hiding 
places, one can see how easy it is for the roach to appear 
as gregarious, but there probably is no more social ten. 
dency in the life of the roach than in any other member 
of the Orthopterous group. 
While the roaches are dark-loving creatures, there is 
a behavior that indicates a response which is so aptly 
called differential sensibility. This can be tested by sud- 
denly lighting up a roach infested cellar. The creatures 
run frantically until they come within the shadow of a 
post; there they stop short, and may easily be picked up. 
They seem certain of safety when in this darkness, 
