306 



THE PAXORPOID COMPLEX, 1. 



if this apparently single bristle be cut acnjss near its base, the 

 separate interior channels of the bristles of which it is actually 

 composed can be easily recognised. Thus, we see that the large, 

 male frenular bristle is not formed by liypertrophy of one of the 

 original series at the expense of all the rest, but by fusion and 

 lengthening of the whole set. The longitudinal Huting visible 

 along the somewhat fiatteiied basal part of this bristle is also 

 evidence of its composite nature. 



Text-tig. J d. 

 A\'iiii;-coupling apparatus of Hippotio)i scro/a (Buiyd.), ^ , showing single, 

 strong, frenular bristle, engaged in hasp-like chitinou;; retinaculum 

 developed from the radius (B); viewed from beneath; ( x 14); hi, 

 humeral lobe. 



The ?rfi'nacii/fwi in the male is a highly specialised structure, 

 having no homologue in the female, or in any other insect. It 

 consists of a strong, curved, chitinous catch, directed posteriorly 

 towards the hind wing, and developed from the underside of the 

 strong radius of the forewing, not very far from its base. This 

 structure is hasp-shaped, and forms a very etiicient catch for the 

 frenulum, which is able to slide to and fro within its grasp, 

 during ilight, without running any risk of becoming detached 

 (Text-fig. 15). 



It is curious to note the difference in action required for the 

 coupling (jf the wings in the two sexes, owing to the difference 

 in position of the retinaculum. In the female, we must move 

 the hindwiny sharply forward, and then let it fall gently back, 

 so that the frenulum may become engaged in the catching hairs. 



