260 MAINE AGRICULTURAL, EXPERIMENT STATION. 1916. 



Jowls: The part of the head below the cheeks and the eyes 

 (Wingate) ; also known as the cheeks or gense. 



Lateral mouth-hooks: Heavy, black, chitinized, curved hooks or 

 thorns on the head segments but separated from the jaws by an inter- 

 vening space, in which respect they differ from the mouth-hooklets 

 (q. v.), as also in being usually shorter and broader at the base (Figs. 

 30-4A; 3i-6?c; and 33-uc). 



Mouth-hood: A dorsally convex, ventrally concave, chitinous termi- 

 nation of the cephalo-pharyngeal skeleton of the larvae of certain types, 

 which covers the anterior opening of the alimentary canal. (Fig. 34- 

 ?F}. 



Mouth-hooklets: Chitinized, black, microscopic thorns, elongate 

 and slender or short and thick, situated closely at the sides of the jaws 

 and evidently of assistance in prehension (Figs. 33-1 id; and 35-jc and 

 </). 



Posterior larval spiracles: See posterior respiratory organ. 



Posterior respiratory or breathing organ, appendage, tube or 

 process: An appendage borne terminally or dorsally on the twelfth 

 (last) larval segment, consisting of two tubes more or less completely 

 fused mesad throughout their length, enclosing two large trachese and 

 bearing on their ends the posterior larval spiracles (q. v.) through 

 which the trachese open. This tube is considered for descriptive pur- 

 poses to have been originally a terminal appendage; consequently its 

 length is the distance from its base (where the tube becomes differ- 

 entiated from the last segment) to its apex ; its width is the maximum 

 transverse diameter across both stigmal plates (q. v.) ; and its depth 

 or height is the maximum dorso- ventral distance at the tip when ori- 

 ented as described above; (when the tube is very short and directed 

 dorsad, what appears to be the cephalo-caudad distance). 



Pupal respiratory cornua: A pair of chitinous terminations of the 

 tracheae leading to the prothorax of the developing fly, which are pushed 

 through the puparium, dorso-cephalad, for respiration during the pupa 

 stage. Their surface bears a few or many denticles or papillae about 

 which the air enters. Sometimes very conspicuous, sometimes (especi- 

 ally on the puparia of aphidophagous larvae) exceedingly minute and 

 indistinguishable (Fig. 30-7/4). 



Segmenta,! bristles, hairs, spines or vestiture: A transverse row 

 of more or less prominent hairs or other armature, specialized from the 

 integumental vestiture (q. v.) across the dorsum and sides of each 

 larval segment. These hairs are twelve in number, and for convenience 

 in description, I have named them in order, beginning with the pair 

 nearest the mid-dorsal line and proceeding laterad and ventrad : a, 

 median; b, dorsal; c, dorso-lateral; d, lateral; e, posterior ventro -lateral; 

 and f, anterior ventro-lateral. 



Segmental elevation or cone: A more or less prominent conical 

 fleshy elevation subtending a segmental bristle (q. v.). 



Slit-like spiracle: One of the three pairs of openings of the 

 tracheae at the posterior end of the body of the larva, on the stigmal 



