1929] 
Myrmecocoles of Formica ulkei 
211 
Batrisodes is slower, moving- between 65 and 80 centi- 
meters a minute on the average, and Leptinus testaceus was 
found to be the slowest species examined, averaging 30 to 
50 centimeters a minute. Usually testaceus is more rapid in 
its running than the pselaphids, attaining a much higher 
speed than the average cited, but its frequent pauses bring 
down the average time. When testaceus is unduly stimul- 
ated, instead of running rapidly away as do the ulkei 
workers and Tachyura, it tends to letisimulate. Thus in one 
series of trials it averaged five periods of death-feigning 
per minute and covered on the average only 4.2 centimeters. 
Such behavior, in addition to its hiding proclivity, would 
indicate that it met danger first by rapid darting, and then 
finally seeking safety in immobility, with the head and 
prothorax deflected and the antennae and legs more or less 
protected by the shield like margins of the body. At least 
the death feint, so-called, is pronounced in the species when 
induced by contact stimuli, and the resulting quiet state 
may be a reflex response. Whether such a condition would 
prevent its being attacked is problematical. 
As would be expected, individual beetles showed individ- 
uality in their rate of locomotion, some being consistently 
faster than others, and one testaceus was far more prone to 
letisimulate than any of the others used. 
Similarly, there was a gradual loss of activity in the 
laboratory animals, their rate of locomotion being much 
higher when brought in from the nests than several days 
later. 
Despite such complicating factors entering into the 
question of activity, the species used showed a differential 
speed of running, and this fact may be significant. Thus 
these observations make it probable, and indeed rather 
obvious, that the predative inhabitants (synecthrans, 
Wheeler, (1926), by the very conditions of their existence, 
should be more active, and move faster than the less 
persecuted synoeketes and symphiles, and the latter slower 
than the synoeketes. Exceptions of course are to be ex- 
pected. 
