264 CLAUDE FULLER. 



There are two points of difference between the antenna? of 

 H. viator and those of an}' other species at present coming- 

 under reference. In the first place the minimum number of 

 joints for all castes is twenty-four, whereas in other species 

 the maximum is twenty-one. In the second place H. viator 

 imagos exhibit fewer oints than do their lai'gest workers; in 

 species of other genera workers or soldiers may have as many 

 joints as the imagos, but never more and frequently less. 



All the imagos I have examined from south-west Cape to 

 as far north as the Orange River agree in having XXVII- 

 or XXVI-jointed antennas, and a XXVI is always due to the 

 presence of one compound joint near to the base of the 

 flagellutn. The number XXVII therefore approaches a 

 specific character ; it appears due to the subsidence of joint- 

 multiplication during the fourth instar and before a possible 

 fuller expression has been reached. 



The antenuEe of workers rauge from XXV to XXX in an 

 unbroken series, and the rule is, the larger the individual the 

 greater is the number of joints. As the largest workers have 

 more joints in their antenna? than do the imagos it is assumed 

 that in the former caste the larger insects lean more towards 

 the primitive condition. 



As the differences in the antenna? of workers and of soldiers 

 ai'e only differences in the joint totals, it is supposed that 

 they are due to more or less joint-multiplication taking place 

 in the fourth instar. If joint-multiplication ceases at the 

 beginning of the instar there are twenty-five joints; if later 

 there are more. However, the XXX expression for the 

 lai"gest workers cannot be regarded as a possible maximum, but 

 rather as a specialised limitation, because in the lai'ger and 

 more generalised species of the genus the largest workers 

 may possess organs of as many as thirty-five joints. In the 

 soldier antenna? the totals range from XXIV to XXVII, and 

 here, as with the workers, size and number go together. The 

 lower minimum and maximum are probably traceable to 

 cephalisation. 



Development. — Unfortunately it has not been possible to 



