CASTES OF TERMOPSIS 499 



develop:\iext 



The eggs of T. angiisticollis are long, slender, and reniform. 

 In living eggs, and after fixation, two sizes may be noted : the small- 

 est eggs are about 1.3 mm. long; the larger ones range from 1.5 to 

 1.7 mm. I am unable to state what these size differences may 

 imply. 



The youngest nymphs of T. angusticollis that I have examined — 2.2 

 to 2.5 mm. long, with eleven and twelve antennal segments — are all 

 alike in external appearance, but with a lens the two types of fertile or 

 reproductive nymphs and sterile or soldier nymphs may be seen. The 

 heads are of similar size, but the large brain, almost filling the head 

 cavity of the reproductive nymph, is clearly distinguished from the 

 smaller brain of the soldier nymphs, and correlated with the brain 

 structure is the whiter denser abdomen of the reproductive nymphs 

 and the more transparent abdomen of the soldier nymphs. In stained 

 and mounted specimens the larger sex organs of the reproductive 

 nymphs are in marked contrast to the smaller ones of the soldier nvmphs 

 (Thompson, '19, p. 385). 



The origin of the soldier, in late njTnphal life, from a wingless, 

 rounded, worker-like nymph, has been described by several 

 writers. Lespes ('55) described this origin of the soldier of L, 

 lucifugus, and Snyder ('15) saw it in L. flavipes, L, virginicus, 

 and T. angusticollis. Knower ('94) saw the nasutus of Eutermes 

 rippertii (?) (Nasutitermes pilifrons) molt from a worker-like 

 skin. The writer can add one more example of the late origin of 

 the soldier from a previous work-Uke phase in the species Termop- 

 sis nevadensis. In May, 1919, a dealated first-form male and 

 female of T. nevadensis, together with about fifteen wingless 

 nj-mphs, which were thought to be young third forms, were collected 

 at Pacific Grove, CaUforinia, and placed in a small glass vial with 

 fragments of pine wood. The vial was brought to Wellesley in 

 July of the same year, and when the contents were examined a 

 white newly molted soldier was found in place of one of the wing- 

 less njTnphs. 



Fuller ('20), p. 248, writing of the origin of the soldier, states: 



It is even very difficult to state exacth' when the distinguishing 

 characters of soldiers and workers first become discernible. In certain 

 species examined it would appear that slight differences can be detected 



