Pairing of the Plebeiid Blue Butterflies. 



165 



the dorsal armature above to the margin of the ring and 

 bases of the clasps below, pierced by the anal aperture 

 and by the aedeagus, without any trace of scaphium or 

 any anal armament, no gnathos and no sinus or armament 

 of any sort round the aedeagus. 



The aedeagus is thus held practically in one spot, with 

 no antero-posterior movement, and only some possibility 

 of varying in direction, considerable in the separated parts 

 on a slide, but probably little or nothing in the living 

 animal. Besides this fixity the Plebeiid aedeagus has 

 another peculiarity — the free portion, that beyond the zone, 

 is extremely short. This is most extreme in the genera 

 Polyommalus and Agriades, apparently least so in Plebeius 



Fig. 6. — Diagram of aedeagus of Agriades bellargus, showing 

 absence of sinus and brevity of free extremity. 



(aegon) and Aricia (astrarche), in which there is a con- 

 siderable external portion, chitinous, however, only on one 

 aspect, in which it ends in a point ; the other aspect is 

 membranous (eversible), reaching up, in a sharp angle, close 

 to the zone. (Pis. XXVII, XXVIII, XXIX, also see figs. 

 1 and 4, PL V, p. 101, Ent. Rec, vol. xxii.) 



One must, therefore, take this prolongation to be merely 

 the extremity and not part of the shaft. The peculiar 

 specialisations of the male appendages in the Plebeiids 

 appear to be, as regards the aedeagus, its fixity by the 

 zone being in the floor of the genital cavity without any 

 sinus, and probably its fixity in direction also, during fife, 

 however much it may appear movable on a slide ; its 

 position close under the dorsal armature, and its separation 

 from the clasps by a large smooth area of the floor of the 



