( 320 ) 



Abdomen. 



The iiulirication oi the alulominal ses>iiients is exactly the same as in tiie 

 earwigs. The iiitersegineiital merahranes, which are quite concealed from view in 

 nou-ilissecteil sjiecinieiis, hear laterally luiiuerous sliort hairs, tlie hairy area Ijeing 

 especially large on the underside. The first tergite forms ])art of tiie thorax aud 

 resembles the thoracic tergites in being rounded at the sides. There are eleven 

 tergites altogether in the small as well as the large specimens, counting the 

 pygidinm (or telson) as a separate segment (PI. XVI. tigs. 2, 3 ; PI. XVII. fig. 8). 

 The nintli and tenth tergites are the shortest. The tenth has a hum]) in the centre 

 clothed with longer bristles. The pygidinm is rounded, its upperside being 

 convex. 



The first abdominal segment has no sternite. The eighth sternite (= sternite 

 of the eighth segment) is the largest, and moreover differs from the others in being 

 evenly rounded posteriorly from side to side (PI. XVI. fig. 2). The ninth sternite 

 is smaller than all the preceding ones. It is narrowed at the apex, which is 

 truneate-emarginate, the sides being rounded proximally and incurved distally, 

 While in Jlrm/merus and Forfictda the tenth sternite is represented by two 

 ihitinised plates placed at the base of the cerei {xtg, PI. XVIII. ^g. T), 

 respectively callipers, in Arixenia the two plates are quite membranaceous. 



The callipers of the earwigs are represented in Arixenia by a pair of cerci, 

 which are liairy, like the body, and almost circular in a transverse section. They are 

 non-segmented, and therefore agree with the cerci of Hemimerus, and not with the 

 segmented cerci of certain immature earwigs : Diplotaxi/.%, Karschiella, etc. The 

 cerci are longer, slenderer, and less curved in our small specimens of Arixenia than 

 in the larger specimens. In the individual figured the left cercus is a little longer 

 than the riglit one. This, we think, is accidental. Unfortunately the left cercus is 

 broken in our second large specimen. lu the smaller specimens the right cercus is 

 as long as the left one. 



We may presnme that in adnlt Ari.renin similar sexual differences will be 

 I'onnd as in the earwigs and Hemimerus. It was the close agreement in the 

 abdomina of the small and large Arixenia which first aroused onr suspicion tiiat 

 all our specimens might be immature. 



Respiratory System. 



The position of the spiracles is exactly the same as in Hemimerus and the 

 earwigs. The stigma situated on the prothorax {sti, PI. XVII. fig. 8) is much 

 larger than the others. On the meso- and metathorax the spiracles are placeil 

 behind the eiiimerum, being concealed underneath the lobe of the latter. 

 The seven abdominal stigmata are situated in front of the upper anterior 

 angle of the sternites of segments 2 to 8. The tracheae agree on the whole 

 with those of the common earwig. 



ITervous System. 



Here, again, Arixi'tiia does not present any essential characters which would 

 remove it from among the Dermaptera. The main chain consists of eleven ganglia, 

 namely, the sujira- and iufra-oesophageal ganglia, three thoracic and six abdominal 

 ones. The infra-oesophageal ganglion escaped Dufour's notice in the earwigs,* 



• Ann. Sci. A'ut. xiii. p. 361 (182li). 



