1921] Crampton: Sclerites of the Head 69 
certain Diptera, the epipharynx may become long and stylet-like, 
forming with the labrum, the so-called labrum-epipharynx. In the 
orthopteroid insects the epipharyngeal region usually does not project 
to any great extent, and in such cases consists of the membranous inner 
lining of the labrum and clypeus (i. e., the “roof of the mouth ”) bearing 
hairs and taste organs frequently arranged about a Y-shaped thickening 
near the median region. In certain of these orthopteroid insects, the 
labrum may be partially divided into an anterior and posterior 
area called the antelabrum and postlabrum, by an incomplete transverse 
suture or by emarginations of the sides of the labrum. 
As was previously mentioned, Riley, 1904, considers that the 
clypeus, together with the labrum, frons, etc., arose from the first or 
protocerebral segment of the embryo. The clypeus, labeled ‘‘cl’”’ in 
all Figures, extends from the labrum (or the labral suture) posteriorly 
to the clypeal suture, which, however, may be obsolete in some insects. 
When the clypeal suture has disappeared, the posterior limits of the 
clypeus are demarked by a line drawn across from the base of one 
mandible to the base of the other mandible, since the clypeal suture, 
when present, corresponds in general to such a line connecting the bases 
of the mandibles, which are therefore the chief “landmarks” delimiting 
the posterior extent of the clypeus. This fact is of considerable im- 
portance, since the area usually called the clypeus in the Psocide, etc., 
lies behind the line connecting the bases of the mandibles, and is there- 
fore in all probability an anterior portion of the frontal region. 
The entire clypeal region may be but slightly chitinized and pig- 
mented, giving the appearance of a membranous area, as is the case with 
the region labeled “‘cl”’ in Fig. 79 of a larval Lepidopteron, or in Fig. 39, 
of the termite Mastotermes. In other instances, as is the case in the 
Neuropteron Raphidia, shown in Fig. 33, and less clearly in the earwig 
shown in Fig. 36, the posterior region ‘“‘pe”’ of the clypeus may be 
strongly chitinized and pigmented, while the anterior region ‘‘ac”’ 
is not strongly chitinized and pigmented (i. e., has a membranous 
appearance) thus differentiating the entire clypeal region into an 
anteciypeus “‘ac’”’ and a postclypeus, “pe.” Occasionally, the clypeus 
is divided into an anteclypeus and a postclypeus by a transclypeal 
suture extending transversely across it. 
In the larva of the Neuropteron Sialis, shown in Fig. 40, the clypeal 
region ‘‘cl’’ is retained in a condition more nearly approximating the 
primitive, or original one. If one will compare this larva with those of 
the Neuroptera Raphidia and Corydalis, shown in Figs. 41 and 42, one 
may see that while the clypeal suture extends clear across from the base 
of one mandible to the base of the other in the larval Sialis shown 
in Fig. 40, (i. e., the line of the posterior border of the area ‘“‘cl”’ extending 
from the base of one antenna to the other) this same clypeal suture is 
broken or interrupted in the larvze shown in Figs. 41 and 42. In other 
words, the clypeal suture, usually extending from the base of one 
mandible to the other, extends only from the base of the antenna 
labeled ‘“‘bat”’ to the frontal pit “fp” on either side of the head of the 
larvee depicted in Figs. 41 and 42, while the median portion of the 
