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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 81 



of the head. The maxillae are suspended in the usual manner by the 

 articulations of the cardines against the margins of the hypostomal 

 areas of the postgenae (C, Cd, E, e). 



NMb 



(2 Sg-R-^ Hst t=^ D 



Fig. 51. — Structure of the posterior and ventral parts of the head of a 

 caterpillar. 



A, postero-ventral view of head of a noctuid (Lycaphotia iimrgaritosa). B, 

 dorsal view of»same. C, interior view of postgenal and hypostomal regions, 

 showing posterior arm of tentorium (PT), and articulation of cardo (Cd). D, 

 inner face of same region in Malacosoma americana. E, ventral view of right 

 half of cranium, with mandible and antenna, of Estigmene acraea. 



a, posterior articulation of mandible; Ant, antenna; 4AP, base of adductor 

 apodeme of mandible; AT, anterior arm of tentorium; c, anterior articulation 

 of mandible ; Cd, cardo ; dap, dorsal apodemal plate of postoccipital ridge ; e, 

 articulation of cardo to cranium; FrR, frontal ridge; Hst, hypostoma ; /, line 

 of base of neck membrane; j, hypostomal suture, hypostomal ridge ; Lb. labrum : 

 Md, mandible; Mx, maxilla; NMb, neck membrane; Pge, postgena ; PoR, post- 

 occipital ridge; PT, posterior arm of tentorium; Tnt, transverse bar of ten- 

 torium ; vap, ventral apodemal plate of postoccipital ridge. 



The foramen magnum is extraordinarily large in the caterpillar, 

 being almost as wide as the cranium, and is extended forward dorsally 

 in the median notch of the vertex (fig. 51 A). The postoccipital ridge 

 {PoR) is inflected from the rear margin of the cranial walls, there 



