150 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 81 



^5. — Second dorsal dilators of the pharynx (fig. 55). — Origins on 

 epistomal ridges near union with frontal ridge ; insertions dorso- 

 laterally on pharynx. 



26. — Third dorsal dilators of the pharynx ( fig. 55) . — Each arises on 

 cranial wall laterad of origins of antennal muscles ; extends medially, 

 posteriorly, and downward to insertion on pharynx just laterad of 2-,. 



The insertions of muscles 24, 2§, and 26 all lie posterior to the 

 frontal ganglion connective. 



2/. — Fourth dorsal dilators of the pharynx (fig. 55). — A group of 

 fibers on each side, arising on outer surface of lower end of frontal 

 ridge ; converging to one or two stalks inserted on dorsal wall of 

 pharynx just before brain. 



The following dorsal muscles are inserted behind the brain and on 

 the region of the stomodeum that may be distinguished in the cater- 

 pillar as the oesophagus, but which is the so-called posterior pharynx 

 in Orthoptera. 



28, 2p, 50. — Dorsal dilators of the oesophagus (fig. 55). — Three 

 fans of muscles arising on posterior margin of cranial walls on each 

 side of vertical emargination ; the spreading fibers inserted dorso- 

 laterally on oesophagus from brain to crop. 



J/. — First ventral dilators of the pJuirynx (fig. 55). — A pair of 

 long slender muscles arising on transverse bar of tentorium (fig. 53 

 D, Tnt), converging to ventral wall of pharynx where inserted just 

 behind first ventral transverse muscle {d) . 



^2, 55. — Second and third ventral dilators of the pharynx (fig. 55). 

 — A pair of small muscles on each side arising on extreme outer ends 

 of transverse tentorial bar ; fibers spreading at insertion ventro-later- 

 ally on pharynx just before anterior circular muscles of oesophagus. 



34' 35> 3^- — Ventral dilators of the oesophagus (fig. 55). — Three 

 large fans of fibers arising on postoccipital apodemes on each side 

 laterad of posterior roots of tentorium ; the spreading fibers inserted 

 ventro-laterally on oesophagus from circum-oesophageal nerve con- 

 nective to crop. 



THE MUSCULATURE OF BACK OF HEAD, AND NATURE 

 OF THE INSECT NECK 



The head of the caterpillar is remarkably mobile. It is provided 

 with a wonderful system of muscles, the fibers of which arise mostly 

 in the prothorax and are distributed at their insertions upon the post- 

 occipital ridge of the head in such a manner as to enable the caterpillar 

 to make all possible head movements of which it conceivably might 

 have need (fig. 57 A, B, C). 



