NO. 7 



THE INSECT CRANIUM SNODGRASS 



21 



the cleavage line in the nymphal cicada (fig. 5 A, B, Fr), it might he 

 supposed that in the aphids the frons has been entirely obliterated. 



Finally, it may be noted that a method of ecdysis having no relation 

 to that in other insects occurs in the Aleyrodidae and Coccidae. In 



Fio. 6. — Heteroptera. 



A, Oncopclfus fasciatus (Dallas), Lygaeidae, head of nymph. B, Cimc.v 

 Icctularius L., Cimicidae, head of nymph. C, same, exuviae of head, ventral. 

 D, Acrosiernnm hilare (Say). Pentatomidae, exuviae, dorsal. E, Mergantia 

 histrionica (Hahn), Pentatomidae, head of nj'mph. F, Oncopclfus fasciatus 

 (Dallas), Lygaeidae, section of head (simpHfied from Butt, 1939), showing 

 distribution of cibarial and precerebral pharyngeal muscles on frontoclypeal 

 area of head. G, Graplwsaiita italicum (Miiller), Pentatomidae, section of head 

 (from Weber, 1930), showing cibarial and pharyngeal muscles occupying entire 

 extent of dorsal wall of head. 



Trialeurodes vaporarimn (West.), as described by Weber (1931), 

 at each of the first three larval ecdyses the cuticle is split around the 

 anterior end of the body between the dorsal and ventral surfaces, 

 and the emerging insect pushes the exuviae ofif the rear end of the 

 abdomen. At the final ecdysis there is formed also an anterior marginal 



