NO. 3 



INSECT IIEAl 



-SNODGKASS 



in-gans belong to the second head segment behind the prostomiuni. 

 and acquire their facial positions secondarily by a forward and upward 

 migration. \^entrally the frons is limited, and separated from the 



Fig. 46. — Modifications in the facial structure of the insect head. 



A, Forficula auricularia. B, Fopillia japonica. larva. C, Ftcrotiidca rihcsi. 

 larva, inner surface of front of head. D, J^espa imcidata, well-chitinized_ larva. 

 E, Pteronidea ribesi, adult. F. Apis mcUifica. G, Psocus vcnosus. H, Magicicada 

 septendecim. I, molted skin of an Aeschna larva. 



Aclp, anteclypeus; Ant, antenna; AT, anterior arm of tentorium; at, anterior 

 tentorial pit; c, anterior articulation of mandible; Clp, clypeus ; dt. attachment 

 of dorsal tentorial arm to head wall ; cs, epistomal suture ; Fr. frons ; fr, 

 " adf rontal " ; Lm, labrum; O, ocellus; .v, suture of Forficula diverging from 

 end of coronal suture ; SgR, subgenal ridge ; t, molting split in Aeschna larva 

 diverging from end of coronal suture, but is not frontal suture. 



clypeus, by the epistomal suture (fig. 46 B, es), except when this suture 

 is lacking. If a median ocellus is present, it is situated in the upper 

 angle of the frons (figs. 46 E, 47 B). The muscles of the labrum, 

 some of the dilator muscles of the pharynx, and the retractors of the 

 mouth angles, when present, have their origins on the frons. By 



