1951] 
Brown and Cheng — Psilobethylus 
147 
for holotype were very similar to it, but were lighter and 
more yellowish in color, lacking the gastric infuscation. 
The total length in the El Paso County (type locality) 
series ranged for three specimens from 1.63 to 1.70 mm. 1 
Head length 0.35-0.42 ; alitrunk length 0.45-0.56 mm. ; 
cephalic index 66-69. 
One of the two El Paso County paratypes was dissected, 
and the maxillary palpi proved to be composed each of 
one cigar-shaped segment with slender, curved base; the 
single segment bears a low welt on the lateral face near 
midlength. The labial palpi are two-segmented, the apical 
segment robust, ovoid, fitting snugly into the curved, 
trumpet-shaped basal segment. The palpal segmentation 
in combination with the mandibular dentition may prove 
of value at some future date in differentiating the Ameri- 
can forms from those of the Old World in which the labial 
palpi are stated to have one segment. 
One female (figure 2) from Santa Rosa, Tabasco, Mex- 
ico, in a Berlese funnel soil sample with ants and col- 
lembolans, Aug. 16, 1945 (F. Bonet). Total length 1.79 
mm., head length 0.39 mm., alitrunk length 0.60 mm., 
cephalic index 71. This specimen is much like the holo- 
type, but is pale yellow in color. The two basal teeth of 
the mandibular series are much reduced, smaller than as 
shown in figure 3. 
Three specimens from Urbana, Illinois, Feb. 18, 1945 
(J. L. C. Rapp) taken in soil. Like the holotype but head 
a bit more convex dorsally and ventrally and also at the 
sides, in this respect tending toward foveolatus. Size, 
color and particularly the very similar sculpture ally this 
sample with lucidus and not foveolatus. Cephalic index 
75-78. 
One specimen, Duke Forest, Durham, North Carolina, 
June 2, 1945, “oak on sand, 2 inches deep,” (A. S. Pearse). 
Total length 1.99 mm., head length 0.43 mm., alitrunk 
length 0.62 mm., cephalic index 73. Head shape inter- 
mediate between those of Texan and Illinoian specimens. 
1 Conditions of measurement and range of error as in corresponding 
measurements for Ps. foveolatus n. sp. 
