62 
Psyche 
[March-June 
TWO NEW FORMS OF MONOMORIUM (FORMICIME) 
By Robert E. Gregg 
Department of Biology, University of Colorado 
In the Nearctic fauna we have one very widely distributed 
species of Monomorium ( M . minimum (Buckley)), and several 
other species of more local occurrence, and while minimum is a 
quite variable ant, it seems not unlikely that some of the varia- 
tions may be distinct populations that warrant recognition. 
Examples of such are present in my collection, and are here 
described with the conviction that they are valid, although sub- 
sequent information might make it necessary to alter this con- 
clusion. 
Monomorium peninsulatum sp. nov. 
Plate 9. 
Worker . — Length 1. 8-2.0 mm. 
Head almost rectangular, convergence anteriorly nearly im- 
perceptible; occipital angles abrupt but rounded, posterior 
margin straight; clypeus produced in front and furnished with 
two carinae which project as distinct, sharply pointed teeth be- 
yond the border; posterior clypeal margin extending deeply 
between the frontal carinae, which are short and do not continue 
far behind the antennal insertions. Antennae 12 -segmented, the 
last three segments forming a distinct club; scape failing to 
reach the posterior angle of the head by a distance equal to 
\y 2 times its width at the apex; mandibles evenly curved, 
4-toothed; maxillary palpi 1 -segmented; labial palpi 2 -seg- 
mented. Eye separated from mandibular fossa by a distance 
equal to 1% times its diameter. 
Thorax at the rounded humeral angles % as wide as the head; 
long and narrow, in profile moderately and evenly arched; 
mesoepinotal impression distinct and fairly deep. Epinotum 
with rounded angle, so that the basal and declivious faces pass 
gradually into each other; epinotal spines absent. Petiolar sur- 
face rounded, the sides subparallel and the superior border 
