409 



The legs are more densely hairy in jacohsoni than in esau and 

 somewhat longer, but the proportions and structure of the 

 tarsal segments are almost the same in the two species. Although 

 Arixcnia is remarkably pubescent, the soles of the tarsi are less 

 hairy than in true Earwigs. The claw-segment has no pulvillus 

 and the claws are of the same form as in true Earwigs. 



Abdomen. 



One of the most important and interesting distinctions between 

 the sexes of Dermaptcra, and between the immature and adult 

 females, is the great reduction in the adult female of the eighth 

 and ninth abdominal tergites, which segments are not visible 

 externally in the imago of that sex. x'Vs Hemimerus agrees in 

 this respect with the other Dermaptera, it is very remarkable 

 that in Arixcnia both sexes have the full complement of tergites, 

 the reduction of the tergites 8 and 9 being very slight in the 

 female. This retention of a larval or ancestral character places 

 Arixcnia apart from all the rest of the order. Similarly, the 

 callipers of Arixcnia, too, are of a larval type, but this point 

 Arixcnia shares with Hemimerus, in which the callipers also do 

 not assume the strongly chitinised polished type found in most 

 adult true Earwigs, remaining hairy and being round in a trans- 

 verse section. But the callipers of adult Arixcnia are more 

 earwig-like than those of Hemimerus. They are thickest at 

 the base and taper to a point, the extreme tip being hard and 

 naked. In the adult male they are directed at first outward 

 and then bowed inwards at an obtuse angle. At this elbow 

 (and beyond it) they bear on the inner surface short spine-like 

 bristles which curve frontad and are doubtless of service in copu- 

 lation (text-fig. 28). The callipers of the female and all immature 

 stages are almost straight. There is no trace of segmentation 

 in the larvie and adult. These forceps are too long and weak 

 in both sexes for being ehective weapons of offence or defence. 

 In those Earwigs in which the forceps are apparently useless as 

 weapons, they are highly specialised in the male for sexual 

 purposes. We must look upon the callipers of Arixcnia as being 

 either very primitive or extremely degenerate. 



The posterior segments of the abdomen situated in between 

 52 



