1929] Myrmecocoles of Formica ulkei 205 
that the ulkei workers are, the mouth-parts being most 
stimulating to the beetles. 
Finally, the mouth-parts of ulkei workers have been wiped 
as dry as possible and then covered with a drop of saturated 
sugar solution. The incurva sucked or licked the mouth- 
parts as dry as though the fluid had been regurgitated by 
the ant. To see whether or not the laboratory sugar solution 
would be eaten if given them as such, drops of the fluid 
were placed on bits of paper or wood, and the incurva fought 
and gathered about these drops until they had eaten all of 
it, as though the species were accustomed to such a diet in 
nature. 
In addition to this varied diet of incurva, the species has 
also been seen to devour crushed larvae and pupae of the 
host ant, Formica ulkei, and the myrmecocolous staphyli- 
nid, Atheta polita as well as attack the larvae of the 
syrphid, Microdon, taken from the same host nest, when 
the latter’s soft, ventral creeping surface was exposed. 
From such observations one obtains a fragmentary pic- 
ture of the place held by Tachyura incurva in the ulkei 
biocoenose, viz., that of a relatively unmolested species feed- 
ing upon the stores of food carried in by the ulkei workers, 
and attacking both the host ants, and the other co-inhabi- 
tants of the nest when these are dead or disabled. It is pos- 
sible, although improbable, that the incurva may even creep 
up and steal some of the regurgitated fluid being given to a 
worker ulkei by another, as is the custom of certain synoe- 
ketes (Atelura formicaria), although its general habits 
tend to place the species in the role of scavenger. In 
return for this abundance of food and protection from 
the enemies of the carabidae (birds, toads, insectivorous 
mammals, and predaceous insects in general) which give 
the ulkei mounds a wide berth, the incurva perform the 
doubtful favor of aiding in removing nest refuse, a task 
which is ably performed by the ants themselves. 
Response to Moisture 
Other things being equal, the temperature of the ulkei 
mounds is more constant than that of the surrounding 
