14 



this valve, the pharynx; posterior to this valve, oesophagus. These limitations 

 of the oesophageal region will be found convenient later, when I compare the 

 mouth-parts and the sucking pharynx of Gulex with those of other diptera. 



The tip of the labrum-epipharynx seems to turn upward (fig. J, lr-e), altho 

 the opening is upon the ventral surface, as may be seen in fig. 6, l>, whiqh 

 represents the ventral view of the tip of this part. The tip of the labrum- 

 epipharynx is comparable to a quill-pen with three tips near each other, the 

 middle one of these three tips being slightly shorter than the other two. The 

 two lateral portions of the epipharynx, as seen in section, when they near the 

 tip, lay themselves closely upon the sides of the tubular portion, passing upward 

 upon it, as seen in fig. 5, lr-e; they thus serve to strengthen the two outer 

 points of the tip of the epipharyux, while] the labrum continues to a sharp point 

 at the tip, and, united with the upper surface of the epipharynx tube, forms the 

 middle point of the tip. The channel, or slit, along the under side of the epi- 

 pharynx, widens toward the tip, leaving thus an opening for the passage of fluids 

 into the tube of the epipharynx. 



The labrum itself is a thin lanceolate lamella of chitin, concave along the 

 under side from the basal portion to the tip, and its concavity rests upon and 

 fits- to the convexity of the tubular part of the epipharynx, to which it is so 

 lightly attached that they readily separate by application of caustic potash. The 

 outer edges of the labrum roll slightly inward toward the epipharynx along most 

 of its length. (See fig. 6, d.) At its base the labrum sends a chitiuous support 

 beneath the clypeus, where it separates more from the epipharynx and has its 

 own muscles, indicating that the labrum has a degree of motion independent of the 

 epipharynx, a motion allowed, perhaps, by the elasticity of the connection between 

 the labrum and epipharynx. The muscles of the labrum (fig. 9, p>n ') are inserted 

 upon the upper side of its base and have their origin on the inner surface of 

 the roof of the clypeus. These muscles are, at least in the females of Cule.i' 

 rufus, divided into three portions in their upper part, as shown in fig. 9. 



The hypopharynx of the female of Culex is a linear, lanceolate, transparent 

 lamella of chitin, with a longitudinal rod through the middle, the nature of which 

 will be discussed later. At its base the hypopharynx forms the continuation of 

 the under wall of the pharynx. (See fig. 11, /;.) The hypopharynx is closely 

 pressed upon the under side of the epipharynx, completing the tube nearly formed 

 by the epipharynx. No muscles have their insertion on the base of the hypo- 

 pharynx. Its tip is simply lanceolate (fig. 5, A). In CuUx pipicnx and C. rufus 

 nothing further is visible (with a magnifying power of five hundred diameters), 

 in sections of the thicker middle portion of the hypopharynx, than a simple 



