NO. 2 DRAGONFLY LARVA — SNODGRASS 9 



ventral (posterior) wall of the mandibular cavity. The numerals here 

 used to designate muscles are those given by the writer (1952) to cor- 

 responding muscles in the head of the cockroach. The two mandibles 

 of Anax are of the same size and shape, have the same dentition, and 

 flat molar areas proximal to the second set of teeth. When the jaws 

 are closed the points of the teeth slightly overlap. 



Maxillae. — The larval maxillae are typical generalized maxillary 

 appendages, except for the absence of galeal lobes (fig. 3C). The 

 sharply toothed laciniae {Lc) lie beneath the mandibles (A). A slen- 

 der outer lobe {C,Plp) is sometimes regarded as the galea, but the 

 fact that it is provided with two basal muscles (E) shows that it is 

 the palpus ; a galea has but one muscle. The odonate maxillae make 

 the usual maxillary feeding movements of protraction and retraction 

 against the sides of the hypopharynx. In the retracted position 

 (A, Mx) the cardines are folded dorsally above the stipites, where 

 they are articulated on the cranial margin (C, a') just in front of the 

 posterior tentorial pits. In protraction the laciniae are thrust forward 

 beyond the mandibles, and they doubtless grasp the prey brought back 

 by the labium to deliver it to the mandibles. 



Hypopharynx and cibaritim. — The hypopharynx of an Anax larva 

 is a relatively small, cushionlike lobe with a flat under surface pro- 

 jecting downward between the anterior ends of the maxillae (fig. 3 A, 

 Hphy). It is separated from the base of the labium by a wide mem- 

 branous space between the maxillary stipites. Just behind its base is 

 a deep pit containing the orifice of the salivary duct (slO). The scle- 

 rotic lateral walls of the pit are continuous above with the hypo- 

 pharynx itself, and come together ventrally below the salivary open- 

 ing to form a V, from which is given off posteriorly a large T-shaped 

 or anchor-shaped apodeme (fig. ^h,hAp). The apodemal support 

 clearly corresponds with the fulcral arc of the hypopharynx of a 

 cockroach, and the apodeme is merely a continuation from it. The 

 common salivary duct (slDct) traverses a groove on the dorsal side 

 of the apodeme (D), and on the arms of the apodemal base are in- 

 serted the tentorial retractor muscles of the hypopharynx (A, D, 16). 

 The hypopharyngeal apodeme is a characteristic feature of the dragon- 

 fly larva. Its shaft extends posteriorly through the head below the 

 tentorium, and the terminal crossbar is embedded in the posterior lip 

 of the base of the labial postmentum, where it is held in place by small 

 apical brushes of fine fibers. From a process on the under surface of 

 the apodeme arises a pair of long, slender muscles (A, E, 20) that 

 enter the labium to be inserted on the base of the prementum (fig. 

 5 A). These muscles evidently correspond with the very short muscles 



