i8 



more of the adherent skins of its eariier ecdyses. After a care- 

 ful examination of the sacs of a large number of species, it would 

 appear that the full number of larval moults is four (or possibly 

 even five) but in some species the number may be reduced. At 

 least in the case of a species of Neodryinus that was most closely 

 investigated the number of ecdyses cannot be less than four (in- 

 cluding that from larval to pupal condition) as is evident from 

 an examination of the sac. In this genus the sac is partially 

 removed to form a cover for the cocoon when the larva leaves 

 its host. This cover is subovate or reniform and consists of two 

 distinct larval skins attached to one another, longitudinally fis- 

 sured at the moults and spread out valve-like, the smaller sur- 

 rounded by the larger. Each of these skins is pierced by nine 

 spiracles of which one (at the one end of the series) is indistinct 

 in the larger skin. Besides these, one still smaller skin is left 

 beneath the wing-lobe of the host and this is also distinctly 

 pierced by a series of spiracles. It is possible that there is yet 

 another smaller skin more internally placed, though this was 

 not observed. Therefore there are at least four and possibly 

 five moults in this species. 



POSITION OF THE LARVAL SAC. 



In dryinized Homoptera there is great diversitv in the posi- 

 tion of the larval sac. The position may vary in the case of r 

 single species, or in different species of a genus, or it may be 

 absolutely constant, and not only in a species, but apparently 

 in all the species of a genus. 



In most of the species of Neochelogyniis the larval sac is 

 ventral, and lies immediately behind the posterior coxa ; in A^ 

 coriacens, however, it is placed at the side of the neck. In 

 Faranteon the larval sac is placed either dorsallv or ventrallv on 

 any abdominal segment, as many as six or eight on a single indi- 

 vidual; more rarely it has been found beneath the thorax, at the 

 insertion of the hind coxae or on the prothorax laterally or be- 

 neath. In Pseudogonatopus the sac is always dorsal or dorso- 

 lateral on the abdomen and several sacs may be found on one 

 Delphacid. In P. stenocrani on the nymph of Stcnocmiius dor- 

 salis the sac stands up erect like a wheel in the middle line be- 

 tween the wing-pads, giving it a most extraordinary appearance. 

 All the species of Echthrodelphax, ParadryUius, Thaninato- 

 dryinus and Neodryinus have the larval sac placed beneath one 



