226 Proceedings of the Royal Physical Society. 
labrum are shaded, as are also the cavities of the maxillary foramen and 
the occipital foramen. 
The following parts of the head, already mentioned, will be frequently 
referred to in the classification and detailed descriptions, and they merit 
further consideration :—the frons, the epistome, the clypeus, the labrum, the 
antenne, the mandibles, the maxille, and the labium. 
The Frons.—This region varies little in the various species except in 
its relation to the epistome, which affects its anterior border. In A. 
domesticum the anterior border is transverse. In A. paniceum it is 
slightly curved. In Péilinus pectinicornis it is markedly curved. In 
Rigas: 
Frons and epistome of A. domesticum. 
£. mollis it is indented, and the antennal pits are shallow, as is also 
the case in YX. tesselatwm. 
The Antenne are much reduced. I have been able to distinguish 
only two joints. The antenne vary in size according to the species. 
Perris (loc. cit.) is of the opinion that they are four-jointed, but states 
that he has discerned only two joints, which he figures. 
The Zpistome.—This is a most important region for taxonomic characters. 
For convenience it may be divided into three regions, a median or clypeal 
region adjoining the clypeus, and a region on each side extending between 
the antennal pits and the clypeal region (Fig. 4). This clypeal region bears 
a varying number of bristles. The lateral regions, except in YX. tesselatum, 
are free of bristles. 
The Clypeus—This appears to be a continuation of the epistome. It 
is a thinner plate destitute of bristles. 
