( 316 ) 



and for that reason we have not been able to compare theiu with the collection 

 of earwigs in the British Musenm. 



The mandibles of Ar/:re/iia aj)[)ear to me to be mnch more suitable for brushins!; 

 food into the month than for cntting it np. The length of the bristles placed 

 on the inner edge near the apical teetii speaks against the mandible being nsed 

 for cutting np hard substances, with the exception perhaps of small pieces not 

 so large as the three teeth together. The hook-like shai)e of the bristles also 

 indicates that the mandilile is largely' used as a kind of brush. 



The maxilla, which is represented in fig. 2 of Fl. XVII. from the underside, 

 agrees on the whole with that of the earwigs and Ilemimerus. As in the allied 

 insects, it lies in a deep sinus, bounded laterally by the lateral portion of the 

 capntal capsule, and raesally by the mentum. The lateral edge of this sinus 

 or groove is much less sharply cariniform than in the earwigs. The proximal 

 portion of the maxilla, in live specimens of earwigs, is capable of a strong forward 

 movement, and can slide but little sideways. The latter movement is reserved 

 for the distal parts of the maxillae, which open and shut like the mandibles. 

 In consequence of this opening and shutting and the simnltaneous forward 

 movement of the maxilla the food is hanled into the mouth, which latter at that 

 moment is widened on acconnt of the uuderlip flap]iing downwards and its ai)ical 

 lobes moving sideways. The sutures on the proximal parts of the maxilla are very 

 distinct in Arixenia, and we were surprised to find that the iiart which corresponds 

 to the cardo of other insects consists of two sclerites (PI. XVIl. fig. 2, a 1, a 2). 

 The cardo is generally stated to be one single sclerite in all insects. A comparison 

 of Forfirulfi and [{I'mtmerxs, however, convinced us that also in these insects there 

 is a suture extending, as in Arixenia, from about the centre of the outer margin 

 inward and forward. We can hardly assume that this suture is of secondary 

 origin, but believe the non-divided cardo of insects to be the result of the fusion 

 of two sclerites in consequence of stronger chitinisatioa. The cardo acting as a 

 lever to the maxilla requires to be rigid, especially in insects in which the maxillae 

 are pnshed far forward when feeding, or have to execute abrupt movements. 

 In the earwigs the mouth-parts are relatively soft, and it would therefore be 

 intelligible that here a suture was preserved which had disa]ipeared in more 

 strongly chitinised insects. 



The central portion of the maxilla, the so-called stipes, consists of three 

 sclerites (PI. XVII. fig. 2, bl, b 2, b 3). The inner and the median sclerites 

 (b 1 and b 2) are hollowed out on the upperside for the reception of the mnscles. 

 The two apical lobes cl (= lacinia) and c2 (= galea) resemble those of the 

 earwigs. The inner lobe is armed at the apex witli two teeth which stand one 

 beside the other, the longer one being dorsal and the smaller one ventral. Both 

 teeth are claw-like, their apical surface being convex and the proximal surface 

 concave. The inner margin nf the lacinia gradually widens proximally, so 

 that the molar surface thus formed represents a narrow triangle, the point of 

 which lies at the apex of the lacinia. The two sides of this surface bear each 

 a single row of stiif bristles. This row becomes more irregular proximally, 

 where additional bristles appear on the lateral surfaces near the edge, and 

 some also in between the two rows. The stiff bristles are slightly bent twice, 

 reminding one of the letter S. The lacinia of Hemimerus has four apical teeth 

 instead of two as in Arixeiiia and Forfcula, and the edges of the inner margin 

 are very thin and cariniform, the molar surface being deeply hollowed out. 



