Rhynehart — Lije- History and Bionomics of the Flax Flea-Beetle. 513 



(34). Midway between the two large bristles, which occur near the frontal 

 suture at each side, there is a minute puncture, which sometimes carries a 

 more minute bristle. Just ventral to the lateral margin of the epicranium 

 another strong bristle occurs, and antero-ventral to it is a puncture. Ventral 

 to the antenna there is anteriorly and near the pleurostomal margin a strong 

 bristle, whilst a small one arises ventral to and near the posterior extremity 

 of the insertion of the first antennal segment. 



The frons carries a transverse row of four long, strong bristles, which 

 arise just on the posterior margin of the epistome. Posteriorly, and in the 

 order given, there are present also on the frons two small bristles (one at 

 each side of the frontal ridge), two punctures, and, well back towards the 

 epicranial suture, two further punctures. 



The close similarity between this arrangement of bristles and punctures 

 and that commonly found on the head capsule of Lepidopterous larvae is very 

 apparent, and is here referred to because of the interest which such similarity 

 affords from the phylogenic point of view. 



The clypeus is provided with a transverse row of what appear to be 

 bristle-follicles or punctures, but close examination reveals very minute 

 bristles in them (PL XVIII, tig. 35). The number does not appear to be 

 constant ; four at each side is the usual condition, although an additional 

 one is ofien present at either side. 



The antennae (PI. XVIII, fig. 28) are situated on the lateral margins of 

 the epicranium, and just posterior to the pleurostome. Each consists of 

 three segments,' the basal one being large, flattened, and in close contact 

 with the head. The middle segment is smaller, more cylindrical, and is pro- 

 vided with a number of sensory structures towards the apex. These consist 

 of: — a long, blunt, prominent process, which arises on the inside of the 

 segment, and projects inwards and forwards ; three short and blunt spines, 

 which arise from rounded pits ; and one or two similar pits devoid of such 

 spines. All these structures are on the dorsal aspect of the segment. The 

 terminal segment is sub-conical, inclined to be somewhat pear-shaped, and 

 is not provided with any sensory appendages. 



Ocelli are absent. 



(ii) MoiUh 'parts.— T\iQ labrum (PI. XVIII, fig. 34) is light yellow in 

 cleared preparations, and somewhat triangular in shape. The free margin 

 is distinctly tripartite and arched dorso-ventrally. Each outer lobe carries 

 five strong blunt bristles, which arise from the ventral surface near the margin, 

 and curve inwards towards the centre, while the middle lobe is provided 



1 Some writers regard the flat basal segment as a projection from the head. In this 

 paper it is considered a distinct segment. 



