DEVELOPMENT OF THE ANTENNA OP TERMITES. 249 



O. latericius series I have been able to sort out the soldiers 

 on the basis of the internal metamorphosis of the mandibles. 

 These organs practically assume their adult character on 

 entering the fourth instar ; the heads of callow soldiers 

 generally partake, however, of the worker type and may be 

 wider than long. With 0. latericius the change in the 

 shape of the head from a subcircular to an elongate-oval 

 outline takes place during the last ecdysis. Further, in the 

 progress of the fourth instar the mandibles of all its castes 

 become more and more deeply chitinised and coloured. This 

 chitinisation starts at the tip and extends gradually to the 

 base, the heaviest deposit being, with workers, along the 

 cutting margin. In the last ecdysis of soldiers and workers, 

 chitinisation, as manifest by pigmentation, has its principal 

 seat in the head, the capsule and antennee becoming pig- 

 mented. In the case of certain species a considerable degree 

 of pigmentation of the antennee of imago nymphs takes place 

 in the fourth instar. The two main growing periods of the 

 imago nymph are the fourth and fifth instars. 



3. THE TERMITE ANTENNA. 

 (1) Composition. 



All termite antennae are composed of two sections — a scape 

 and a flagellum. The scape is two-jointed, the number of 

 joints in the flagellum is variable, ranging from nine to thirty 

 and more. This subdivision of the oi-gan is fundamental. 

 With a few exceptions the two joints of the scape are robust 

 and cylindrical — a shape they retain throughout development. 

 The flagellum, often composed of joints of different shapes 

 and sizes, may exhibit both specific and caste differences, and 

 such distinctions may be radical or confined to differences in 

 number or size of the segments. There is little variety of 

 outline to be met with and few, indeed, depart from the 

 moniliform type. Perhaps the most unusual is that exhibited 

 by the soldiers of Psammotermes allocerus. 



In many antennaj the conventional joint III is longer than 



