1883.] MR. J. WOOD-MASON ON THE FAMILY EMBIID^. 631 



cerci attached to its huge and firmly chitinized podical plates, perfect 

 in its symmetry. 



Turning to the lower or ventral surface of the animal, and countino- 

 as before the "segment mediaire" as the first abdominal somite, we 

 find a series of nine sterna, corresponding to the nine basal terga', all 

 likewise visible without dissection, the eighth and ninth not "bein"- 

 shortened any more than are their terga, nor concealed from view by 

 any enlargement and production of the seventh, as they are in the 

 Cockroach and in the Earwig, and the tenth alone being hidden bv the 

 overlapping posterior margin of the nintli. The abdomen, in fact, in 

 this insect is, so far as its eighth and ninth somites are concerned, 

 less modified than in either of these two forms, thus resemblino- that 

 of Gnmpodea. Between no two of the eight basal of these sterna 

 is any aperture to be detected in the middle line, nor is there any 

 between the ninth and tenth, the former of which is identical in 

 shape and texture with the seven basal ones ; but the eighth is 

 shorter and differently shaped from those which precede it, its hinder 

 angles being produced and rounded so as to form in its hinder border 

 an emargination, to the bottom of which is movably articulated by 

 its base a triangular plate, whose basal angles are divided off from it 

 by sutural lines; between the eighth sternum with its triangular 

 plate and the ninth lies a wide and membranous space conspicuous 

 by its white colour, and in it an aperture, which is ordinarily concealed 

 by the triangular plate. As no other median aperture save the anus 

 exists, this must be a genital aperture, and since it is placed, as in 

 the females of the Cockroach and the Earwig, between the eio'hth 

 and ninth sterna, and since moreover the genital aperture of winged 

 specimens is situated, as in the males of the same two insects, one 

 somite further behind, it must be the female genital aperture, and 

 the insect a female. 



Capture of Males. — Several winged specimens were captured 

 during 1880 in my dining-room, whither they had been attracted 

 by the lights. After flying for a while round and round the lamp 

 in the centre of the table, they settled and walked about the cloth 

 with a most peculiar gait, by which they were always readily recoo-- 

 nizable, and which appeared to be due to locomotion on all sixes over 

 such a surface being rendered impossible or awkward for tliem by 

 the peculiar structure of their fore legs. 



These insects, which undoubtedly belong to 0. saundersii, are all 

 of the same uniform brown colour. 



Later, a winged specimen of another species was brought to me 

 by one of the Museum assistants, who had found it clinging to the 

 mosquito-curtains of his bed, a position in which insects th;it have 

 been attracted by the lights of the house over night are not uufre- 

 quently to be found in the morning. This specimen is black. 



Description of the Male Sexual Characters. — All the winged speci- 

 mens examined by me agree with the above described female insect in 

 the number of their externally visible terga, differing from it in havino- 

 an unbroken and mesially imperforate series of nine, instead of eio'ht, 

 sterna ; their genital orifice must consequently lie behind the ninth 



