DEVELOl'MENT OF THE ANTENN.E OF TERMITES. 263 



The potential development of an antenna to the third 

 ecdysis seems to be twenty-three joints. That is, it may 

 arrive at the stage M, which is pseudo-XX-jointed. At this 

 stage III contains six elements, there are fifteen abjuncted 

 joints and the two-jointed scape. The two species, T. belli- 

 cosns and T, natalensis, may be cited in this connection. 

 The antennae of these ab ovo are in stage C, which is a 

 potentially fifteen-jointed (I +11 + 0+0 + 0+0 + 9 

 to 1). Their development therefore represents an increment 

 of eight, and the same is the case with those species such as 

 Odontotermes latericius, of which the ab ovo expression 

 is the pseudo-XII of stage A. 



This leads me to surmise that the elimination of joint multi- 

 plication with or soon after the third ecdysis was the most 

 important step in the reduction of the antenna. With 

 images the ai'rest coincides with the beginning of a period of 

 special nutrition, a pi'eparation stage for a long fast, a fast 

 including the tending and feeding of young. The curtail- 

 ment of development is therefore directly traceable to the 

 social habit, the multi-jointed organ of the non-social ancestor 

 being sacrificed to a new necessity. 



•2. STUDIES OF SPECIES. 



(1) Hodotermes viator {LatreiUe). Fig. 5, a—g. 



Antennal Index. — Imago XXVII, XXVI ; soldier XXVII, 

 XXVI, XXV, XXIV ; worker XXX to XXV. 



In all castes and in all species of the genus Hodotermes 

 the antennas are very much alike, irrespective of the number 

 of joints of Avhich they are composed. This is mainly traceable 

 to the curtailment of joint-multiplication and the subsidence 

 thereof not being accompanied, to any noticeable extent, 

 by the formation of compound joints. It is also partly 

 due to the simple annular nature of the majority of the 

 segments. Compound joints are not entirely absent, but 

 wheu present are located in the more juvenile section of the 

 flagellum and are never conspicuous. 



