1921] Crampton: Sclerites of the Head ral 
frontoclypeal region bearing the labels “fr’’ and “‘pce”’ in Figs. 41 and 
42, although the original extent of the frons “‘fr’’ is retained in the insect 
shown in Fig. 40. 
A line drawn across between the bases of the antennze divides the 
frons into an antefrons and postfrons in certain insects, and in these 
forms, the postfrons is usually united with the upper region of the 
head capsule. A narrow transverse region called the epistoma “‘eps”’ 
of Fig. 38, becomes secondarily marked off in the anterior region of 
the frons of certain beetle larve, etc., and in certain sawfly larvae, such 
as the one shown in Fig. 32, a region labeled “‘eps,’’ which may corre- 
spond to a portion of the epistoma is marked off by a faintly impressed 
line. MacGillivray, 1913, refers to the region “‘eps’’ of the sawfly 
larva shown in Fig. 32, as the “‘first clypeus,’’ and to the true clypeus 
‘‘oce”’ and “‘ac”’ as the “second clypeus.’”’ The region ‘“‘eps,’’ however, 
is elearly a portion of the frons, since it lies behind the clypeal suture 
extending across‘from the base of one mandible to the other, and while 
the region labeled ‘“‘eps’’ in Fig. 32 does not correspond to the entire 
area bearing the label ‘‘eps’’ in Fig. 38, it does in a way correspond to 
the epistcma, or to a portion of the epistoma, and may therefore be 
regarded as a greatly reduced epistoma. 
It is possible that the area labeled “‘fr’’ in Fig. 76 represents the 
anterior region of the frons (antefrons) rather than the frons proper, 
although for the sake of convenience, it has been referred to simply as 
the ‘‘frons’’ in the following discussion. In the Psocidz (sensu lata), 
however, the regicn usually referred to as the “‘frcns”’ is clearly the 
antefrons (or anterior region of the frons) alone, while the posterior 
region of the frons in these insects is frequently indistinguishably 
united with the region of the head behind it. 
The frons was spoken of above as an unpaired region of the head, 
and this is true of most insects. In the beetle larva shown in Fig. 38, 
however, a median dorsal infolding or ‘‘implex”’ of the head capsule is 
formed, resulting in the production of an internal ridge for muscle 
attachment, and an external suture (corresponding to the internal 
ridge) which extends forward into the frontal region “‘fr,’’ dividing it 
into equal halves,* as is shown in Fig. 38. 
If we adopt from vertebrate anatomy the term “frontal region”’ for 
the frons, and the term “occipital region’”’ for the portion of the head 
capsule about the occipital foramen, it is but logical to call the region 
between the frontal and occipital regions the ‘parietal region,’’ since 
the parietal region occupies this position in the vertebrate skull. The 
term ‘‘parietals’’ has therefore been adopted for the region between 
the frons and occiput (i. e., the region labeled ‘“‘pa”’ in all Figures) in 
the following discussion. Some entomologists apply the term ept- 
cranium to the parietals; but properly speaking, the epicranium includes 
not only the parietals, but also the frons, gene and postgenz as well, 
and it is preferable to have a distinct designation for the parietals. 
*It is quite probable that the region labeled ‘‘fr’’ in Fig. 38 represents the 
post frons, rather than the entire frons, since it lies behind the antenne (in the 
postfrontal region). 
