J. T. WADSWOliaill l.")? 



pharyngeal apparatus when chitinisation oi' the oral segment takes 

 place. They can be observed on larvae about 7-8 weeks old, but they 

 are very minute, measuring about 12/x in length and 8/i in diameter ; 

 in larvae of this age there can be seen in addition, a number of small 

 pa])illae bordering the dorsal and dorso-lateral lobes of the mouth. 

 The line radiating grooves wiiit-h surround the mouth have already 

 been referred to. 



The complete cephalo-pharyngeal skeleton consists of three pairs 

 of sclerites and an unpaired V-shaped sclerite. The mandibular 

 sclcrites or " great hooks " each possess a prominent anterior tooth, 

 a smaller median tooth, and a basal tooth or spur, and each sclerite 

 is perforated near the base by a small aperture ; Hewitt (1907) described 

 a similar perforation in the corresponding sclerites of the larva of 

 Anthomijia radicuni L. The mandibular sclerite articulates with the 

 intermediate or hypostomal sclerite, which in U . solslilialis appears 

 to be fused with the posterior or cephalo-pharyngeal sclerite ; in this 

 latter sclerite there is a deep indentation posteriorly between its dorsal 

 and ventral prolongations, and these again are frequently bifurcated. 

 With careful observation a membrane can be observed surrounding 

 each prolongation extending some distance behind them ; a corre- 

 sponding membrane is figured by Mik in U . cardui. 



A V-shaped sclerite is situated beneath the hypostomal sclerites ; 

 each free end of the V articulates with a ventral projection of the 

 hypostomal sclerite on each side, and the apex of the V is placed near 

 the bases of the two mandibular sclerites (Fig. 8). It may be called 

 the sub-hypostomal sclerite. The examination of a number of prepara- 

 tions of the cephalo-pharyngeal apparatus reveals numerous slight 

 variations in size, shape, and amount of chitinisation of these structures ; 

 these variations are more especially noticeable in the posterior sclerite. 

 Interposed between the mouth and the mandibular sclerites there is 

 found another strongly chitinised body ; this only becomes apparent 

 towards the close of the feeding period, and probably consists of the 

 closely apposed and chitinised sides of the oral lobes. 



In appearance and structure, the anterior and posterior spiracles 

 are very similar to those of U . cardui figured and described by Mik ; 

 he described the anterior pair as being situated on the second segment 

 (of the pupa). In U. solstilialis the anterior pair are placed dorso- 

 laterally on the third apparent segment, and near its posterior border, 

 about 0-3 mm. apart (Fig. 11). They are yellowish-brown in colour 

 and do not project above the surface of the body ; each spiracle consists 



11-2 



