512 Scientific Proceedings, Royal Dublin Society. 



line already referred to, which extends from the junction of the epicranial 

 and frontal sutures along the median line to the epistome. This is the 

 frontal ridge (frr.), and is obviously a strengthening hand of chitin. The 

 dorsal surface of the head is therefore divided into three distinct areas : — the 

 epicranial region (epc.) at each side, and the frons. The epicranium extends 

 ventrally to the fleshy stipes of the maxilla, and supports the antenna laterally 

 and towards the anterior margin. 



The frons is sub-triangular, and has along its anterior margin a very 

 strongly chitinised narrow region — the epistome. The latter is emarginate 

 anteriorly for the clypeus (cL), and extends laterally to the pleurostome {pis.), 

 which provides, on its anterior margin, articulatory surfaces for the condyles 

 of the mandibles. The clypeus is a narrow transverse band, extending 

 between the epistome and the labrum. It is little chitinised, and pale yellow 

 in cleared preparations. Anteriorly it is emarginate for the labrum, the 

 posterior margin of which is situated venti'al to the clypeus, so that normally 

 the articulation for the labrum is along the ventral surface of the anterior 

 margin (PL XVIII, fig. 34). The ventral surface of the head (PI. XVIII, 

 fig. 25) shows the fleshy protruding maxillae, between which is the globular 

 submentum (sm.) of the labium. Posterior to the submentum is a mem- 

 branous region, little chitinised, which corresponds to the gula (gu.). Between 

 it and the prothorax there is no distinct suture, and it may therefore be 

 regarded as an anterior extension of the prothorax. 



The maxillary and labial palps project antero-ventrally, and the mandibles 

 cross beneath the labrum, so that normally none of the mouth-parts except 

 the labrum is visible in dorsal view. 



The study of the arrangement of the bristles (setae of many writers) on 

 the head-capsule is important, for, as already pointed out by workers 

 on Lepidopterous larvae, they may prove to be highly useful in the differen- 

 tiation of closely allied species (29). Generally speaking, the head bristles 

 on Z. parvulus larvae are in transverse rows, somewhat similar to those on 

 the body, to be described later. Each lateral region of the epicranium carries 

 on the dorsum two pairs of strong bristles, one pair being beside the frontal 

 suture and the other towards the lateral margin. Slightly anterior to, and 

 medianly from, the latter pair of bristles a round clear spot, resembling 

 the follicle of a bristle, occurs in the chitin. Following Heinrich (29), such 

 spots are called punctures. Towards the posterior angles of the epicranium 

 there occurs at each side a series of five such punctures, in which very 

 minute bristles may sometimes be seen. These occupy a somewhat similar 

 position on the head to the ultra-posterior punctures (secondary punctures 

 of Heinrich) described for various species of Lepidopterous larvae (7), (30), 



