NO. 3 



INSECT HEAD SNODGRASS 



133 



Further evidence that the area thus designated the clypeus in the 

 lepidopteran larva is the true clypeal area, and not the frons, is given 



Fig. 50. — Head structure of caterpillars : anterior cranial wall, labrum, 

 antenna, and mandibular muscles. 



A, anterior surface of head of Lycophotia {Peridroma) margaritosa. _B, 

 same of Thrydoptervx cphemeraefonnis. C, same of Sibeiic stimulca. showing 

 areas of origin of "mandibular muscles (4, 5a). D, antenna of Malacosoma 

 amcricana, left, anterior view. E, interior view of anterior wall of head of 

 Prionoxyshis robiniae (Cossidae), with labral muscles and adductor of left 

 mandible in place. F, anterior surface of head of Mnemonica aurocyanea. G. 

 labrum of Lycophotia maryaritosa, anterior view, showing muscle insertions. 

 H, fronto-clypeal area of same. I, inner view of same. 



AT, anterior arm of tentorium; c, anterior articulation of mandible; Clp. 

 clypeus ; ER, epistomal ridge ; cs, epistomal suture ; Fr, frons ; jr, " adf rontal " ; 

 fs, frontal suture; h, submarginal thickening of clypeus; Lm, labrum; Md, 

 mandible; Nv, antennal nerve; Tra, antennal trachea. 



by the origin of the clypeal dilator muscles of the stomodeum upon it 

 (fig- 55. 20, 21). Finally, it is to be observed, the muscles of the la- 

 brum, which, in all cases where the identity of the facial plates is clear, 



