394 CAROLINE BURLING THOMPSON. 



The differentiation of the worker-soldier nymphs of E. pili- 

 frons into the worker and the soldier is nearly parallel with the 

 development of these two castes from the worker-soldier form 

 in the genus Reticulitermes, Thompson (1917, pp. 123-125); the 

 chief difference being the age of the respective nymphs, the 

 differentiation being visible in E. pilifrons in nymphs 2 mm. long, 

 while in R. flavipes it was first observed in nymphs 3.75 mm. 

 long, although, from the maturity of the frontal gland, it could 

 probably be seen in an earlier phase. 



My work upon this species of Eutermes is in perfect accord 

 with the work of Knower (1894), who noted the absence of 

 young soldier nymphs in the colonies of E. rippertii (?) = E. 

 pilifrons Holm., and who later saw a young soldier of this species 

 emerge by molting from a worker-like skin. The mandibles on 

 the skin were large, as in Eutermes workers, while those of the 

 emerging soldier (nasutus) were small, like those of the adult 

 nasuti. The head of this nasutus was light in color and not yet 

 fully elongated. 1 



Bugnion (1912) states that the soldier (nasutus) of E. lacustris 

 is differentiated at the time of its emergence from the egg, and is 

 distinguished from the other newly hatched nymphs by a long 

 frontal process or horn, and a frontal gland with an excretory 

 canal. His description is as follows: 



"Larve de soldat, longue de 1.32 mm, venant d'eclore (Fig. 12). 

 Cette forme est particulierement interessante parce qu'elle 

 montre une petite corne implantee au dessus du front. Elle 

 donne ainsi la preuve que la caste 'soldat' se differencie deja 

 dans 1'oeuf. La corne, tres courte, ne depasse pas le niveau des 

 pieces buccales. On voit aussi, par transparence, 1'ampoule 

 cephalique entouree de muscles et, a la base de la corne, le canal 

 excreteur." 



Now, although I am fully in accord with the view of Bugnion 

 that the castes of termites are not produced by food or other 

 external influences, and that they are due to intrinsic deep- 



1 Snyder (1915) has also described the origin of a soldier nymph from a worker- 

 like form in Reticulitermes flavipes and R. virginicus. The nymphs were found in the 

 quiescent stage that precedes a molt, and the emergence of the young soldiers was 

 observed. In this case, too, the mandibles of the emerging form differed from those 

 on the cast skin. 



