126 Proceedings of the Royal Physical Society. 
Head and Mouth-paris. (Plate VII.) 
Head (Figs. 1, 2).—The chief feature of the head is the absence of well- 
defined regions. Viewed from above, there is no division into frons, 
epicranium, or vertex as in the ground beetles such as Harpalus. Labrum 
and clypeus are absent. The anterior border of the head is therefore the 
epistome, which lies like a bridge over the mandibles. It is not sharply 
defined posteriorly, but it can be made out as a slightly raised ridge bearing — 
rows of bristles. In the middle of this ridge a U-shaped depression 
surrounded by a slight elevation probably indicates the remains of the 
clypeus and labrum. From this depression a more or less distinct 
median line runs backwards to the line of the eyes, which are easily 
recognised. On either side of this line, lying anteriorly, is a well-marked 
depression. Viewed laterally, the absence of definite regions is again a 
feature of the head. The eye with its supra-orbital ridge, the pregena 
and the antenna with its triangular scrobe or pit, are the chief features. 
Viewed from beneath, the head shows a distinct gular suture running forward 
from the occipital foramen. This suture joins at right angles the pregula, a 
narrow short plate lying between the pregene. Anterior to these plates is 
the hypostome, to which are attached the maxille and labium, | 
Mouth-parts (Figs. 3-6),—These consist of the mandibles, the mazille, 
and the labium. The mandibles are strongly chitinous, triangular in general 
shape. Their inner surfaces each bear three teeth, of which the first or apical 
is the most prominent. They are controlled by two muscles, one (ad. in figure) 
the adductor which closes them, the other (ad. in figure) the abductor which 
draws them apart. The adductor is the larger. Each of these muscles is 
strengthened by a chitinous tendon imbedded in it. i: 
The maaile are of the typical Scolytid type. The cardo is distinct. The 
stipes is fused with the palpifer, galea, and lacinia, but the regions are 
recognisable by the variation of their bristles. A distinct fold serves to 
indicate the line of fusion of the palpifer; this bears a three-jointed palp. 
The galea is indistinct. The lacinia is easily recognised. In addition to 
bristles it bears a row of broader spines which probably serve to clean the 
mandibles of resin, as Blackman has observed in Pityogenes hopkinsi. 
The /abiwm consists of the swhmentum, mentum, ligula, and labial palpi. 
The submentum is peculiar and consists of a forked process adjoining the 
median portion of the hypostome. The labium bears on its dorsal or 
inner surface a well-defined tongue-shaped ligula (Fig. 5) armed with short 
1 Blackman, Observations on the Life-history and Habits of P. hopkinsi, Swaine, Syracuse 
University Techn. Pub., No. 2. 
