208 
Psyche 
[September 
Batrisodes were used in a variant of the above experi- 
ment. The aggregation was allowed to form on the moist- 
ened part, and then additional water was added until this 
area was saturated. Under these conditions, the beetles 
became restless, and the aggregation rapidly broke up, in- 
dicating that too much moisture is as stimulating as not 
enough. This last response has been found for similarly 
induced gatherings of land isopods (Allee, 1926). 
Such gatherings upon moistened areas of filter paper, 
when induced, are not necessarily motionless. At intervals 
one or more of the aggregants will rise and wander about, 
to return usually to the crowded section. Even when the 
group is quiet, individuals frequently tap the paper or one 
another with their legs or antennae. 
Response to Light 
Petri dishes with a diameter of 14.5 centimeters and a 
depth of 3.5 centimeters were so covered with light-tight 
paper that one half of the dish would be in shadow when 
placed under a 40 Watt Mazda lamp giving approximately 
120 foot-candles at 35 centimeters, (measured with a Mac- 
beth illuminometer) . The experiments were run at night to 
avoid light from any other source, and were conducted for 
six trials of a minute each, with a dark interval of half a 
minute between trials. The animals were given a one minute 
adjustment period prior to the first trial of each experi- 
ment, as the species used had a tendency to run rapidly 
about the dish at first. The experiments were short also, to 
obviate the rise in temperature as much as possible, the 
latter being fairly constant, running from 28.5 to 30.5° C. 
for one experiment. The glass top of the petri dish, one half 
of which was light-tight, was rotated 180° between succes- 
sive trials to vary the portion of the dish shaded. 
Under these conditions, the following results may be 
mentioned : 
1. The carnivorus Tachyura incurva, in common with 
many of the related carabids, was photo-negative under the 
experiments as described. This may very well indicate a 
nocturnal active phase, the species being taken through- 
