i66 AGRICULTURAL EXPERIMENT STATION. 



Description of the Larva. 



Structurally the larv?e differ greatly from those of Culex, pos- 

 sessing a very complex respiratory apparatus, adapted to their 

 surface feeding habit. The full grown larva with details is illus- 

 trated on figure 46 and is 6 tO' 6.5 mm. ,=.24 tO' .26 of an inch in 

 length to the end of the ninth segment. The body of the young 

 larva, exclusive of the head and chitinized parts of respiratory 

 tube, is pale yellowish white, almost transparent save for the 

 broad alimentary tract, which is dark gray or black ; large larvse 

 are usually gray or brownish gray, but often clear pale green 

 and only in the latter case is the alimentary tract visible. A 

 longitudinal stripe, broken by the small dorsal plates, runs down 

 the center of the dorsum and is usually white in color, rarely 

 bright pink, and is narrow though widened at each of the seg- 

 mental sutures. The head is rounded, as long as broad, with 

 distinct offsets for the reception of the antennae; pale yellowish 

 brown in color with the basal half of the vertex macidate with 

 brown as shown in figure 46, 2. There is some variation in size 

 either way, or the smaller spots may be consolidated with the 

 larger ones ; but it is always well defined and seemingly very 

 constant in form. This maculation is present also in young 

 larvae and of the same pattern. In the middle of the vertex, in 

 a transverse row, are six rather long, equally spaced feathered 

 hairs and several small, similar ones are situated farther back. 

 The eyes are crescent shaped with a small spot in the concavity. 

 The antenna (fig. 46, 5) is two jointed, the first very short, im- 

 movably attached to the head, the second comparatively long, 

 thickest near the base, tapering evenly toward the apex and ter- 

 minated by six long hairs and tw'o spines,' the latter serrated on 

 one edge. The surface of the second joint is set with small 

 spines, and a four branched hair representing the tuft, is situated 

 on the shaft at about one-fourth its length from the base. The 

 rotary mouth brushes are very small, but dense, and composed 

 entirely of simple hair. The mentum (fig. 46, 6) is somewhait 

 pentagonal in form, the two front angles with five large blunt 

 teeth, the sides with two smaller pointed teeth, and the basal 

 angles greatly elongated. The mandible (fig. 46, 4) is stout and 

 chunky, with two large and several smaller teeth at the apex, 

 and two spines below them which are serrated on their inner 

 edge ; on the dorsal surface are three large curved spines, one of 

 which is simple, the others feathered on one side. A few of the 

 hairs of the dorsal terminal part of the transverse fan are also 

 branched. The maxillary palpus (fig. 3) is elongate, with four 



