Pairing of the Plebeiid Blue Butterflies. 171 



captor's interference, may be doubtful, but there can be 

 little doubt that prehension by the clasps takes place in 

 the first stages of pairing. 



There is a very curious fact, that I suppose to be of 

 constant occurrence, though I have not observed it much 

 more than about a dozen times. This is, that at the end 

 of the pairing the rein is surrounded by a cylinder of 

 amorphous material, certainly not scales or any similar 

 structures, whether a secretion by the male or female, 

 I don't know (see PL LXI and LXII). It easily slips 

 off and is lost; on PL LXI it had left the rein, which 

 retained no evidence of having accommodated so curious 

 an accretion. Whether this ought to be called a sphragis, 

 and whether it is homologous with that structure in 

 Papilionids and Nymphalids I cannot say. 



Explanation of Plates XVIII-LXII. 



Plate XVIII. Appendages of Thecla spini. 



Fig. 1. o, showing free portion of aedeagus 

 to be long and its position close to the clasps, 

 X 25. 



Fig. 2. $, showing ostium (8) and chitinous 

 duct, corresponding in length to the free 

 portion of the aedeagus leading to the 

 bursa, X 25. 



Plate XIX. Appendages of Thecla priuri, showing similar parts 

 to PL XVIII, X 25. 



Plate XX. Appendages of Selenia illustrarin, £ and ?, showing 

 the chitinised duct to bursa (with a hair passed 

 through it) closely corresponds in width and length 

 to the free portion of the aedeagus, X 25. 



Plate XXI. Melitaea athalia, showing large external armature 

 of the ostium, and correspondence between the 

 free portion of aedeagus and the duct with hair 

 passed through it to bursa, X 20. 



