56 The Philippine Journal of Science 1921 
Small soldier—Body short, flat, darker yellow, and more 
heavily chitinized than large soldier; head larger than in large 
soldier, making an angle of about 45° with body. Pronotum 
slightly larger. Otherwise as in large soldier. 
Measurements of Prorhinotermes gracilis sp. nov., small soldier. 
mm. 
Body length 4.30-—5.50 
Head, with mandibles 2.50—-2.60 
Head, without mandibles 1.45-1.50 
Head width: 
Maximum 1.32—1.35 
Minimum 0.90—0.95 
Pronotum width 1.05 
Pronotum length 0.50 
Worker.—Long, slender, very lightly chitinized; thorax nar- 
row, head light yellow, body transparent white, abdomen colored 
dirty salmon to brown by intestinal contents. Head flattened; 
posterolateral region swollen, like P. luzonensis, but eyes only 
slightly developed, projecting very slightly. 
SYSTEMATIC POSITION 
In view of the fact that this is the first case of two Prorhino- 
termes species found living together in the same region, and of 
the further fact that the two species were found in close prox- 
imity and have not been found elsewhere, it would seem an 
obvious inference that we are dealing here with variational 
forms rather than with two distinct species. A consideration 
of the differences between the two species makes this position 
untenable, however. P. gracilis differs much more distinctly 
from P. luzonensis than the latter differs from P. japonicus, 
P. flavus, or P. inopinatus, with regard to which it is indeed 
a possibility that we are dealing with a very variable species of 
wide distribution. The lighter color and lack of chitinization 
and the very slight development of the compound eyes might 
be due to a more sheltered life habit; the size difference might 
be a variation; but the very definite difference in number of 
antennal segments and their shape and size are difficult to ex- 
plain as mere variations. A more detailed study would show 
a host of minor differences and, unless the anterior wing scales 
of the one adult of P. gracilis are abnormal, the wings of the 
two species must differ very greatly. For these reasons I have 
felt it impossible to avoid making this a new species, to which 
I have given the specific name gracilis because of the slender 
form of the worker and large soldier. 
