248 CLAUDE FULLER. 



the front, whilst with images the wing-sacs are withdrawn 

 slowly from their sheaths. With all castes, however, the 

 exuvia is delayed at the head; here it lies for some time in 

 wrinkled folds around the bases of the antennse, and until 

 these organs are withdrawn or the cuticle breaks away the 

 mouth-parts are masked. Even the legs are freed before 

 the head. As a rule the exuvia appears torn away from the 

 anal extremity and individuals are long active before the 

 intima of the proctodEeum is disengaged. 



The second column of the table (fig. 1), representing the 

 phases in the life-history of soldiers and workers, is based 

 genei'ally upon serial examinations of the species T. nata- 

 lensis, T. waterbergi, 0. badius and 0. latericius, 

 and in the main upon the first and last mentioned. 



Apart from the subtle problem as to whether the caste is 

 predetermined in the egg, it is even very difficult to state 

 exactly when the distinguishing characters of soldiers and 

 workers first become discernible. In certain species examined 

 it would appear that slight diiferences can be detected in the 

 third instar. The transformation to a soldier takes place during 

 the third period of quiescency, so that after ecdysis the 

 differentiation is' most decided. A difference between majors 

 and minors of the same caste is observable at the beginning 

 of the fourth instar. The smaller grow but very little and 

 become adult minors. The larger increase to twice their 

 length and several times their bulk and become adult majors.^ 

 Here it is interesting to note that with those soldiers exhibiting 

 a fleshy extension of the labrum, this part is visible as an 

 internal metamorphosis of the third ecdysis and becomes 

 disclosed with the final moult. The serrate nature of the 

 soldier mandible of Psammotermes allocerus is also only 

 disclosed with the last moult. 



From among the quiescents of the third ecdysis in the 



' Accordhig to Kellogg (' Amei'icau Insects,' p. 105) Heath (1902) 

 gives the soldiers of Termopsis angusticollis six moults, three of 

 which are said to take place after differentiation. I have found no 

 evidence of so many moults in the species I have examined. 



