286 Annals Entomological Society of America [Vol. XV, 



batincB, and yet is attached to the gula, as in other species of 

 Paraiulus. 



In female Paraiuli, the second segment and the third are 

 more or less swollen in accordance with the size of the vulvas. 

 The second segment is generally produced ventrad, the ventral 

 margins of the tergo-pleural arch being twisted (Fig. 12, a) 

 and bearing the so-called ventral lobes (/). On the surface 

 of the twisted part occurs a transverse "ventral ridge" (n), 

 surrounding cephalad a large and shallow dimple (u). Accord- 

 ing to species the ventral ridge is more or less irregularly 

 curved, the dimple resulting broader or longer. The third 

 segment shows a still more irregular structure, as it sometimes 

 tapers ventrally (tiganus), and sometimes grows longer {im- 

 pressus-venustus) ; the ventral lobes may likewise be very 

 different or much reduced. 



In Paeromopus ( cf and 9 ) , the ventral region of the three 

 anterior, thoracic segments present a more simple structure, 

 deemed to be archaic. The duplicatures of the collar lobes 

 are more narrow and their angles are evenly rounded (not 

 notched). No ventral lobes are found on the two following 

 segments, the margins of which are diagonally converging 

 backwards, the posterior angles being acute. Under contraction 

 (Fig. 54), the three segments are forced into one another, 

 their ventral margins uniting to build an oval frame, which 

 is closed backwards by the sternal plate of the fourth segment, 

 and in which fit the head with the mouth-parts, the limbs of 

 the first and second pairs and the sexual apertures (vulvae or 

 penis) closely packed together. An exceptional case is likewise 

 found in Paeromopus, as the sternite of the third pair of legs 

 is not fused with the fourth tergo-pleural arch, as usual, but 

 freely articulates with it, a condition realized in the Japanese 

 genera Karteroiulus and Kopidoiulus. 



In all cases the limbs of the first pair remain independent 

 and show no striking particulars ; the sternite is usually missing 

 (Fig. 2). The limbs of the second pair are preserved in Paero- 

 mopus (Fig. 3), and are not coalesced; the sternal plate is 

 scarcely chitinised and only between the stigmata, which are 

 membranous dimples; the tracheal stalks are very long and 

 slender, ribbon-shaped, bent backwards and outwards. The 

 coxas are represented by their basal expansions only, the 

 cylindrical part missing altogether and the telopodites articu- 



