206 
Psyche 
[September 
environment (Holmquist, 1. c.) and the galleries run to the 
superficial water table, and are consequently always moist, 
even in the hot, dry summer months. In such nests a 
temperature and a moisture gradient exists and either of 
these factors, or both, may have important effects upon the 
behavior of the inhabitants of the ulkei nest. 
That moisture is important in the life of testaceus is 
shown by the following experiment : 
Following the technique of Allee (1926), dry filter paper 
was cut to fit the bottom of petri dishes and in three such 
dishes two testaceus were placed. The beetles alternately 
walked, paused or ran about in their characteristic manner 
described later, for an hour and a half. During this time 
they were very active, crawling up the sides to the glass 
roof and then returning to the filter paper. At the end of 
this time a drop of water was placed on the filter paper at 
a definite point (A) on one side of each dish. In each dish 
the beetles located the moistened area within five minutes 
after its absorption. Once, having traveled through this 
wet area, they invariably paused, turned back, and after 
running back and forth in the moist area, each time halting 
at the periphery of the moistened spot, finally crouched in 
this spot and remained motionless, the head and antennae 
resting on the paper. 
This motionless state was broken at intervals and the 
beetles ran about within the spot of moisture, apparently 
at random but trapped by their physiological requirements 
in a way suggestive of trapped Paramecia in acidulated 
water as described by Jennings. 
As the area “A” became larger, and the surface more and 
more dry, the leptinids were correspondingly more and 
more restless, until, with the filter paper with a more or 
less uniform degree of moisture, the beetles had regained 
their normal activity and ran restlessly about. 
This behavior was repeated at will in two of the three 
experimental petri dishes, with the same results. In the 
third the paper was allowed to dry over night by placing 
it on a table and covering it with the glass top, the glass 
bottom of the petri dish being removed. The next morning 
the leptinids were found dead, and strangely enough, in the 
