REPORT ON MOSQUITOES. 251 



pearance is equally gradual, isolated specimens remaining in 

 town until early October and in the field much later. 



The adults die off gradually as winter advances and hiberna- 

 tion is in the egg stage. The eggs are deposited singly on the 

 surface of the water and sink to the bottom, or they may be 

 placed at the edge of a low pool or in the moist mud of a depres- 

 sion from which the water has evaporated. As to the length 

 of adult life, this is probably considerable ; but no definite experi- 

 ments were made and the period of nearly three months is based 

 upon field observations only. At all events it is not a brief one 

 and is reckoned by weeks rather than days. 



Description of the Larva. 



The larva varies greatly in size, measuring from 6 to- 8.5 

 mm., = .24 to .34 of an inch in length, exclusive of the anal 

 siphon. The figures on plate 76 were drawn from a large sized 

 larva. Full grown specimens are yellowish or grayish in color 

 throughout, but when young are almost white, except the head, 

 which is yellow. The head is broadest immediately below the 

 eyes, tapers anteriorly and is rounded in front. There are six 

 small hair tufts of four or five hairs each on the anterior part 

 of the vertex; one at the base of each antenna, the others more 

 central, one pair to the rear of the other. The maculation of 

 the head varies immensely, though it is always symmetrical ; fig- 

 ures 19 to 24 on plate 60, show some of the forms, all of which 

 are common and may be present in a single lot. By far the 

 commonest form, how^ever, is that shown at figure 24 ; a defined 

 brown patch in the center of the anterior part of the vertex and 

 another smaller one in the center or posterior part of the vertex, 

 on a yellow ground color. Entire lots often have this form 

 of maculation, and as there are no other species with similar 

 markings it usually identifies the larva. In young and half 

 grown larvae the heads are wholly pale yellow, save for a slight 

 mark in the center. The antenna (fig. 76, 5) is rather short, 

 curved, thickest at the base, tapering apically ; the surface set 

 with stout spines, the color yellow, becoming darker toward the 

 apex. The apex has one long and short spine, two bristles and 

 a small joint. The tuft is situated on the shaft one-third from 

 the base and consists of six or eight hairs. The rotary mouth 

 brushes (fig. 76, 2) are dense, orange colored and have the hairs 

 pectinated in the more central part. The mentum (fig. 76, 6) is 

 triangular in form, with from twelve to fourteen small teeth on 

 each side of the apex. The mandible (fig. 76, 4) and the maxil- 



