296 L. R. CLEVELAND. 



(3) Third form, which also has three developmental phases: 

 (a) the nymphs, wingless, with white head and body, and eyes 

 that are invisible in the living or unstained specimen; (b) the 

 young adults, no wing vestiges, head and body white, 7-9 mm. 

 long. 



(4) The worker (Fig. 7), wingless, with grayish abdomen, only 

 two developmental phases, i.e., nymphs and adults, salivary 

 glands small and very little fatty tissue is present in the body, 

 blind. 



(5) The soldier (Figs. 8, 9), wingless, with elongated head 

 covered with thick yellowish chitin, mandibles very large, long, 

 dark brown, slender and curved, abdomen shorter than in other 

 castes and more flattened, nymphs and adults only, no post adult 

 growth as in reproductive castes. 



Thompson ('17) showed that the newly hatched nymphs of 

 Reticnlitermes flavipes, i.i mm. long, although externally all 

 alike, could be differentiated by their internal structures into 

 two distinct types, namely, (a) reproductive nymphs, from which 

 the three fertile adult castes develop, and () the worker-soldier 

 nymphs, from which the sterile adult castes develop. By the 

 time reproductive nymphs had attained a body length of 1.3- 

 1.4 mm. they could be differentiated by their internal characters 

 into nymphs of the first form and nymphs of the second form, 

 which developed, finally, into the two respective reproductive 

 adult castes. Soldier and worker nymphs could be differentiated 

 internally by the time they had attained a body length of 3.75 

 mm. Nymphs of the third form could not be differentiated 

 until a body length of 4 mm. was attained. 



These five castes occur in most termites. Known exceptions 

 are: the third form occurs in few, if any, species of the family 

 Termitidae; a true worker caste is not present in the genera 

 7^ermopsis Heer and Neotermes Holmgren, but a large-headed 

 worker-like reproductive form is present; two genera, Kalotertnes 

 Hagen and Cryptotermes Banks, have no worker caste ; the genus 

 Anoplotermes F. Miiller has no soldier caste; some species have 

 as many as three types of soldiers, which, if counted as castes, 

 make these species have seven castes, provided the five described 

 above are all present. 



Grassi ('93) calls the first forms "true" or "perfect" insects, 



