1929] 
Myrmecocoles of Formica ulkei 
197 
strengthen this view, especially since it has a relative 
(Leptinillus validus) with greatly reduced eyes. Another 
related species (Leptinillus aplodontiae) is said to leave its 
rodent host when the latter is killed, and as soon as the 
body begins to cool (Ferris, 1918) , which may indicate some 
degree of parasitic adjustment. All of these leptinids have 
been shown to be closely related to the beaver parasites, 
Platypsyllidae, (Horn. 1882; Riley, 1889). However, they 
are also allied rather closely to the Silphidae morphologic- 
ally (LeConte and Horn, 1883; Sharp and Muir, 1912; 
Imms, loc. cit.), a family which numbers scavengers, as 
well as saprovores and carnivores. 
The various views that have been held are not necessarily 
. mutually exclusive, and it is possible that the Leptinidae 
exhibit a facultative parasitism which would explain many 
of the differing accounts in the literature, and bring into 
agreement the finding of testaceus in habitats suggesting 
phoresy, a guest relationship, an actual ectoparasitism, a 
scavenger existence, or a chance occurrence. 
Leptinus testaceus and other Coleoptera in nests of 
Formica ulkei. 
On October 6, 1928, a trip was made to Palos Park, Illi- 
nois in search of Pselaphidae. Palos is some thirty miles 
south-west of Chicago in the glaciated section of the Chi- 
cago area and is characterized by an oak, elm, hickory sub- 
climax forest in the upland forest sere of this area (Park, 
1929 a, b) . A portion of the Palos sector is inhabited by 
the mound-building ant, Formica ulkei Emery. The ulkei 
community is rather extensive, especially in the more open 
clearings of the forest and along the forest margins. The 
ant has been little studied in nature (Wheeler, 1926). Bur- 
rill and Smith (1918) record the species from Cedarsburg, 
Wisconsin, and in a later paper (1919) mention the finding 
of a larva of the chrysomelid, Coscinoptera dominicana 
(Fab.) in an ulkei nest. Recently, Holmquist (1926, 1928 
a, b) has given the most complete account of this ant in the 
Chicago area, and a note upon a guest ant associated with 
