1921] Crampton: Sclerites of the Head (63) 
make up the region called the postgena by Comstock and Kochi, 1902, 
the hypostoma forming the anterior portion near the mouth, while the 
paragula forms the posterior portion of the postgena. It has seemed 
advisable to thus divide the postgena, since the hypostoma in particular 
is of importance in the study of the head structures of larval C oleoptera, 
Neuroptera, etc. In the beetle larva shown in Fig. 27, a small sclerite 
“pgu’”’ situated on either side of the gula “gu,”’ and bounded posteriorly 
by a paragular suture, has been provisionally homologized with the 
paragula of other insects, although it very probably represents merely 
an anterior portion of the entire paragula. The divided:areas labeled 
“pgu’”’ in Figs. 22 and 29 are likewise not strictly homologous with the 
paragulee of other insects, but it is not worth while to designate them by a 
distinct designation, since they occupy approximately the position of 
the paragular areas. 
The throat region, or the median postero-ventral area of the head, 
labeled ‘‘gu” in all Figures, is called the gula. The gula “gu” extends 
from the posterior border of the head capsule proper to the submentum 
“sm” (Figs. 12, 16, 15, 18, etc.) and is bounded laterally by more or 
less distinct lines or sutures called the gular sutures. Situated on or 
near these sutures are the gular pits “gp” of Figs. 15, 12, 9, ete., which 
mark the position of the posterior ventral arms of the tentorium. 
In some insects, the gular pits mark the posterior extent of the sub- 
mentum, but in others, the gular region extends far forward of these 
gular pits (asin Fig. 12). In such cases, the anterior extent of the gular 
region is marked by a line drawn between the bases of the maxillary 
cardines “‘car’’ (corresponding to the submental suture), or, according 
to Dr. Craighead, the gular region extends forward to the posterior 
attachment of the muscles labeled “11” in Figs 11 and 14. 
The intersternite, “is” of Figs 8, 15, 13, etc., one of the anterior 
plates of the neck region, is ascribed to the gular region by Comstock 
and Kochi, 1902, Riley, 1904, and others; but this plate becomes attached 
to the posterior region of the head in very few insects, and then only 
secondarily. It is homologous with other intersegmental plates occurring 
between the thoracic segments in the lower insects, as was pointed out 
by Crampton, 1917. The pregula, “prg”’ of Fig. 17, is apparently a 
region secondarily marked off in front of the narrow region of the 
throat labeled ‘‘gu’”’ in certain Coleoptera, etc. Its significance is 
not very clear, and there is need of further study of this region. 
In the insects shown in Figs. 20, 21, 24, 26 and 27, the region labeled 
“gu”? may not represent the entire gula, and has therefore been referred 
to as the gular plate in the following discussion. The region labeled 
“gu” in Fig. 7, likewise may not represent the entire gular region, but 
such a narrow, transverse, posterior gular plate is characteristic of the 
Dermaptera, and may serve as one of the diagnostic characters of the 
order.’ 
The origin of the gular region is a very puzzling feature. ‘It is quite 
possible that in some insects the posterior portion of the gular region of 
the adult head may be formed through a chitinization of the mem- 
branous area situated between the ventro-median edges of the head 
