Antennae 



93 



joints, of wliicli the terminal one is very elongate, is 

 really a split tube (fig. 64, 2). This arises from the 

 infolding of the wall of the antenna during the pupal 

 stage. The completely exposed surface bears the long 

 setae, while the folded-in surface is beset with minute 

 elevations of the cuticle. A similar structure is found in 

 other species of Chironomus, and in the female as well as 

 in the male, though it is less marked in the female. The 

 female antenna is scarcely half the length of the male, 

 and consists of eight joints only. The second joint is 

 dilated, but much less so than in the male ; each of the 



Fig. 65. — Enlarged seconil joint of antenna of male Cliironomus-fly. i, side 

 view (transparent). ./; peripheral fibres, eo, end-organs. X 150. 2, upper siarface 

 of ditto, the shaft being removed. X 150. 



next five joints is enlarged in the middle ; the terminal 

 joint is long, but not nearly so long as in the male, and 

 only this takes the form of a split tube. 



The three joints at the base of the antenna differ in 

 structure from those immediately beyond them. The 

 first joint is extremely short, sunk in the head, and 

 almost entirely occupied by the muscles which move 

 the antenna to and fro. The second joint is greatly 

 enlarged, and constitutes a peculiar sense-organ ; the 

 third joint, unlike those beyond it, is smooth, and carries 



