166 Dr. T. A. Chapman on the 



genital cavity, and the extreme shortness of the free por- 

 tion of its shaft beyond the zone. These limitations pre- 

 vent it making any approach to the female parts during 

 pairing, a defect that is made good by the specialisation 

 of the female, enabling the approach to be made by the 

 female and not by the male. The great uniformity of the 

 clasps in the group is no doubt related to this female 

 specialisation ; the fairly uniform dorsal armature has also, 

 no doubt, some special correlated relationship, possibly 

 with the extremity of the ovipositor, but as to this I can 

 make no definite suggestion. 



The figures given of the male genitalia and of the aedeagus 

 separately are more specially referred to in the " Explana- 

 tions of Plates," and need not be detailed again here. As 

 to the Plates, it seemed desirable to restrict their number, 

 else one would have desired to give figures — of a larger 

 number, if not of all the species of the tribe — of both the 

 male and female structures. 



As regards the corresponding female structures, there is in 

 the Plebeiidi, apparently, an even greater departure from 

 the normal structure than obtains in those of the male. 



Considering for a moment the more usual form of these 

 parts we find that in species where the aedeagus is long, 

 it is usual for the cervix * to be long also, and to be, more- 

 over, often chitinised into a solid tube for some distance. 

 This may be seen in many Theclas (e.g. PI. XVIII and XIX), 

 in Apatura (PL XXIII), and in a less degree in many species 

 in which the aedeagus is of average length. In the case of 

 Acraea natalica (PI. XXII), with a very long aedeagus there 

 is also a very long cervix, but it is not very solidly chiti- 

 nised, and in the photograph it will be seen to have twisted 

 somewhat in the specimen, possibly from having been too 

 much macerated. 



It leads to another subject, with which I am not at 

 present anxious to deal — namely, the segmentation of the 

 abdomen in the females of Lepidoptera, but it may often 

 be observed that the ostium is withdrawn (not invaginated) 

 within the margin of the 7th abdominal segment, as 

 may, for example, be observed in Scoparia (see Trans. 

 Ent. Soc. Lond. 1911, PI. XXXV, et seq.); in these cases 

 there is generally no armature. When the ostium has an 

 armature, it generally remains outside the 7th segment. 



* Cervix, or ductus, the duct between the ostium (external 

 opening) and the bursa copulatrix. 



