410 



the callipers and beyond their bases are of special interest in 

 the classification of the Dermaptera, being as a rule different in 

 the sexes. Segment lo, which is proximal to the forceps, is 

 shorter than is usual in Earwigs and bears a rounded median 

 groove in both sexes of Arixenia. Segments ii (= pygidium) 

 and 12 (= metapygidium) are completely fused and form a 

 single sclerite, which, in the ¿, is slightly convex in a sagittal 

 sense and has a round groove dorsally and a less distinct one 

 ventrally. In the ? (text-fig. 23) it is produced into a four- 

 sided pyramid with blunt edges and an elongated dorsal groove 

 and a vestigial round ventral one. 



The apex of the pyramid is sometimes slightly upturned, 

 and the sides are concave proximally for the reception of the 

 callipers. The last or supra-anal tergite (= telson, text-fig. 

 23, tels) is a well-developed transverse plate separated from 

 II and 12 by a suture as distinct as the one between segments 

 10 and II. There are no tubercles and no stink-glands on the 

 abdomen. 



The abdominal sternites 2 to 9 in the male and 2 to 7 in the 

 female are essentially as in other Dermaptera, the first sternite 

 being absent everywhere in the order. The sternite of segment 

 9 diners in the male, and in this sex only, from the previous 

 sternites in bearing joined to its anterior edge a special sclerite, 

 which is large in Arixenia, being a little longer than sternite 9 

 and less than half the width of that segment. This accessory 

 plate is also found in true Earwigs, apparently being different 

 according to species, sometimes large, sometimes vestigial. In 

 Arixenia (text-fig. 14) it is almost membranous with the excep- 

 tion of the edges, which are strongly chitinised. The lateral 

 margins are narrow strips of chitin which curve outward pos- 

 teriorly, here joining a projection from inner (= anterior) margin 

 of the ninth sternite. The proximal margin of the plate is 

 incurved, a kind of fork being formed in which rests the organ 

 of copulation. The sclerite, being somewhat curved upwards 

 and movable up and down, appears to functionate as a support 

 for the penis and a manubrium to the ninth sternite. The 

 muscular attachment has not yet been examined. A compara- 

 tive study of this support in the Dermaptera would be of interest 

 and might furnish important taxonomic characters. 



