626 CAROLINE B. THOMPSON AND THOMAS EK. SNYDER 
of the third form; in contrast with the smaller brain and salivary 
glands, the embryonic, non-functional sex organs, the scanty 
fatty tissue, and the functional jaw muscles of the worker. The 
dark woody masses in the intestinal sac of the worker and their 
absence in the third form are evidence of the worker’s habit 
of masticating wood and the probable diet of predigested food 
in the third form. 
The development of third-form nymphs smaller than 4 mm. 
in length has not been worked out, on account of the difficulty 
of distinguishing them from worker nymphs of similar age. 
The young third-form adults of Prorhinotermes simplex, 
although. wingless and similar to workers in size and general 
shape, are easily recognized by their dark brown body pigment. 
The young and nearly mature third form nymphs, however, 
bear a strong superficial resemblance to their workers, but the 
two castes of this termite may be distinguished by minute points 
of difference very similar to those which differentiate the third 
form and worker of Recticulitermes. 
The venation of the long wings of the first-form adult of P. 
simplex is similar to that of the wing vestiges of the second-form 
nymph. No second-form adults of this species have yet been 
described, although the second-form nymphs are very abundant. 
