NO. 3 INSECT HKAL) SxXOlXIKASS IO9 



l)et\veen the mandibles, and the asymmetrical forms of the hair- 

 covered areas here correspond with the different shapes of the two 

 mandibles. Minute sense organs are scattered over this labral surface, 

 especially on the bare lateral regions. A special group of similar but 

 somewhat larger sense organs lies at each side of the notch in the 

 ventral border of the labrum. The median area of the basal half of 

 the labral surface forms a low elevation, the sides of which are thickly 

 covered with long spine-like hairs curved inward and upward. This 

 elevation projects between the inner edges of the closed mandibles, 

 and its irregular contours fit with the lines of the opposing jaws. Its 

 median surface is depressed and embraces the region of the internal 

 Y-shaped ridge ( /// ) . The elevation is continued upward on the clyp- 

 cal region, above the spreading arms of the Y-shaped ridge, and be- 

 tween the inner recurved ends of the tormae (Tor), and then into 

 the mouth (Mth) and upon the anterior wall of the buccal cavity. A 

 sinuous groove begins upon the elevation ventrally between the tormae, 

 which extends dorsally and enlarges into a deep, median channel con- 

 tinued into the anterior wall of the mouth and pharynx. At the sides 

 of the lower end of the channel, between the slender arms of the 

 tormae, are four asymmetrically placed, oval groups of small peg-like 

 sense organs with large circular bases, partly covered from the sides 

 by fringes of long recumbent hairs. 



The hypopharynx is a large median lobe suspended, as already noted, 

 from the ventral wall of the head between the mouth and the base 

 of the labium (fig. 41, HpJiy). Its posterior end is closely covered 

 by the paraglossal lobes, and its sides are concealed by the mandibles 

 and maxillae. In form, as seen from below (fig. 42 C), the hypo- 

 ])harynx is somewhat ovate, with the smaller end anterior, but its pos- 

 terior end is set off as a narrowed lobe by lateral constrictions. The 

 lateral surfaces of the anterior division fit into the posterior concavi- 

 ties of the mandibles, those of the posterior lobe are embraced by the 

 concave inner faces of the laciniae. The posterior, basal extremity of 

 the hypopharynx projects as a small median process into the salivary 

 cup on the base of the labium (tig. 41 ). The lateral line of the hypo- 

 pharyngeal base is marked bv a slender, sinuous, chitinous bar on each 

 side (zv). The arrangement of the hairs clothing the hypopharynx is 

 sufficiently shown in the figures (figs. 41. 42 C). On its sides and 

 at the posterior end near the salivary cup are a few small sense organs 

 similar to those of the labrum. 



Dorsal to the anterior end of the hypopharynx is an area that leads 

 directly upward into the floor of the mouth. It possibly represents the 

 sternal region of the protocephalic segments of the head. On its 



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