DEVELOPMENT OF THE ANTENN/E OF TERMITES. 257 



(6) Joint Modification. 



. Any decided modification of tlio jijints of the antennae is 

 coincident with an ecdysis and preceded by the subsidence of 

 the process of multiplication. Upon the whole the shape of 



the joints in imago antenna alters only with the last ecdysis, 

 and is mainly restricted to the lengthening out of certain 

 joints in the flagellum. There are also slight changes of 

 form following chitinisation. The antennae of workers are 

 modified but very little; they become pigmented in the last 

 ecdysis and more chitinised after the adult stage is reached. 



With soldiers as a rule multiplication subsides before or 

 during the penultimate ecdysis, and in some species the 

 organ as a whole is so considerably modified during this 

 period of quiescency that after the moult some of the joints 

 have shapes very different from those of the third instar. 

 As a rule the more the shape of the head departs from the 

 larval type the more the antennfe are modified. Later, with 

 ■chitinisation further changes may be accomplished, such as 

 the obliteration of evidence of imperfect articulation. 



Two of the most striking cases are those occurring with 

 the nasuti of the Eutermes group and the soldiers of 

 Psammotermes allocerus. With the nasuti, the remark- 

 able cephalic prolongation called the nasum develops during 

 the penultimate period of quiescency, and at the same time 

 certain of the joints lengthen out in proportion Avith the 

 cephalic projection. Consequently the callow of the fourth 

 instar exhibits a head and a pair of antennae differing very 

 little from those of the final form. In the case of the soldiers 

 of Psammotermes allocerus, after the penultimate ecdysis 

 the antennge present an extraordinaiy change of appearance. 

 The basal series of joints in the flagellum becomes swollen at 

 the base — a reverse of the shape of the undifferentiated 

 and adult stages. Notwithstanding this disparity, they fore- 

 shadow the form of the adult organ, and, later in the instar, 

 the swelling at the base of the joints is transferred to the 

 apex so that they become more or less clavate. 



