NO. 8 ANATOMICAL LIFE OF THE MOSQUITO — SNODGRASS II 



boundaries of the postgenae." This is clearly making anatomy con- 

 form with definitions. The lower parts of the postgenae are mechani- 

 cally strengthened by ridges formed by the submarginal hypostomal 

 grooves. The narrow strips below the grooves, therefore, are simply 

 the marginal parts of the postgenae, so it is immaterial whether we call 

 the bridge resulting from their union hypostomal or postgenal. The 

 grooves are sometimes absent, and the ridges may be marginal on the 

 postgenae. In the mosquito larva the anterior edge of the ventral 

 cranial wall on which the mandibles and maxillae are articulated is the 

 united hypostomal margins of the confluent postgenae. 



From the free cranial margins just mesad of the antennal bases, 

 a slender bar on each side (fig. 7 B, hb) extends mesally, downward, 

 and somewhat posteriorly through the preoral epipharyngeal wall to 

 the base of the hypopharynx (Hphy). Each bar runs close before the 

 mandible of the same side and goes below the narrow lower lip of 

 the mouth (Mth). In Dixa, as shown by Schremmer (1950), similar 

 structures are present but are much wider than in the mosquito larva. 

 The mandibles have their anterior articulation on these rods, a very 

 unusual condition, since the anterior mandibular hinges are typically 

 on the basal angles of the clypeus. The rods have been called "cibarial 

 bars," but there is no defined cibarium in the culicid larva. Since the 

 rods appear to serve principally as suspensoria of the hypopharynx, 

 they are here termed hypo pharyngeal bars. They are the Verbindungs- 

 leisten of Schremmer (1949). Since the hypopharyngeal bars carry 

 the anterior articulations of the mandibles, Menees (1958b) reason- 

 ably argues that the parts of the bars laterad of the articulation are 

 extensions of the clypeus. His identification of the posterior parts 

 with the "hypopharyngeal suspensorial bars of generalized insects," 

 however, is less convincing, since these bars enter the mouth angles 

 and give attachment to the hypopharyngeal muscles, though each may 

 have a lateral preoral branch. 



THE FEEDING ORGANS 



One of the remarkable things about insects is the way their feeding 

 organs are variously adapted to feeding in different ways on different 

 kinds of food. Nothing comparable occurs among the vertebrates, 

 their only adaptation to the nature of their food is in the size, strength, 

 and dentition of their jaws or in the length of the neck. Yet the feed- 

 ing organs of all insects are made up of the same fundamental parts. 

 There is an upper lip known as the labrum, a pair of mandibles, a 

 median tonguelike hypopharynx, a pair of maxillae, and a lower lip, or 



