THE DEVELOPMENT OF THE SOLDIER CASTE IN 

 THE TERMITE GENUS TERMOPSIS. 



HAROLD HEATH AND BLAKE C. WILBUR, 

 STANFORD UNIVERSITY, CALIFORNIA. 



As is well known to the student of the subject, two theories 

 have been proposed to account for the origin of termite castes. 

 According to the first view the young are all alike at the time of 

 hatching and subsequently are modified by extrinsic factors. The 

 second view supports the claim that even before hatching two 

 castes at least, the reproductive and worker or the soldier, can be 

 distinguished by differences in certain of the internal organs. In 

 an effort to determine which of these two theories is the correct 

 one it appeared that the most favorable line of approach to the 

 solution of the problem is through the study of recently established 

 colonies of Torino psis where all of the young belong to the soldier 

 caste. With such material the junior author confined his investi- 

 gations to T. anyusticollis, while the senior author directed his 

 attention to T. nevadensis. As a result the number of molts has 

 been established, the characteristics of each instar have been de- 

 termined and a comparison of the two species at the close of our 

 independent investigations indicates that the history of both spe- 

 cies is, in all essential particulars, the same. 



The number of young appearing in a colony varies according to 

 the nature of its surroundings. Primary royal pairs, occupying 

 burrows in very damp situations, have been found without either 

 eggs or young at the end of eleven months. On the other hand 

 in what appear to be optimum conditions there may be as many 

 as twenty-one individuals of various instars, including one or two 

 fully developed soldiers as well as several eggs in various stages 

 of development. This being the case, a section of the pine belt 

 along the southern shore of Monterey Bay was kept under ob- 

 servation, since the conditions throughout were not only fairly 

 uniform but highly favorable as well. Records kept of census 

 counts in this district during a period of twenty. years may there- 

 US 



