For convenience, the keys to genera and species have 

 been arranged according to the life history stages of the 

 insects. A person wishing to identify a female mosquito 

 will find all the keys for the identification of females, 

 both to genera and to species within the various genera, 

 grouped together in the same section. Keys for the 

 identification of males, larvae, and eggs are grouped in 

 similar fashion. At the head of each section there is 

 included a diagram of the stage concerned. The dia- 

 grams are labeled to show the diagnostic areas or parts 

 mentioned in the keys. If only one species of a genus 

 occurs in Illinois, it is indicated and treated in the keys 

 to genera. Each of the other species is treated in one 

 of the keys to genera; these keys are arranged alphabeti- 

 cally by genera. 



Names of certain genera and species may appear in 

 more than one place in a key. This practice allows the 

 use of a large number of characters for recognizing cer- 

 tain distinctive groups of species within a genus or cer- 

 tain distinctive variations within a species. 



The cardinal directions used for orienting parts of 

 the mosquito body or appendages are as follows: 

 apex — The portion away from the point of attachment; 



concerning the abdomen or its segments, the part 



more distant from the head. 

 apical — On or pertaining to the apex. 

 base — The portion at the point of attachment; in rela- 

 tion to the abdomen or its segments, the part nearer 



the head. 

 basal — On or pertaining to the base. 

 anterior — Forward, toward the head, or in front of. 

 posterior — Backward, toward the rear, or back of. 

 dorsum — The upper part or back. 

 dorsal — On or pertaining to the dorsum, 

 dorsally — In the direction of the dorsum, 

 lateral — On or pertaining to the sides, 

 laterally — In the direction of the sides, 

 meson — The midline down the length of the animal. 

 mesal — On or pertaining to the meson. 

 venter — The under part or belly. 

 ventral — On or pertaining to the venter. 



In the keys, the singular rather than the plural form 

 is ordinarily used to designate the diagnostic parts of 

 which the mosquito has only one on a side, as, for ex- 

 ample, hind femur, eye, antenna, costa. 



Information concerning distribution and habitat is 

 included in the keys. A summary of the distribution of 

 each species is given in the keys to females; information 

 concerning the habitats of the larvae is given in the keys 

 to larvae; and the place of deposition of the eggs is 

 given in the keys to eggs. If the name of a species 

 appears in more than one place in a key, summary infor- 

 mation is included in the place where the largest num- 

 bers of the species will fit. 



DIAGNOSIS OF MOSQUITOES 



An adult of the family Culicidae (Fig. 1), to which 

 tile mosquitoes belong, can be differentiated from other 

 two-winged flies by the following characters; ( 1 ) an elon- 



gate proboscis many times as long as the head, (2) an- 

 tennae which are much longer than the head and are 

 composed of many small, well-separated segments, many 

 segments each with a ring of hairs, and (3) wings with 

 an arrangement of veins depicted in Fig. 6. A pupa 

 is characterized by being active in water, by having a 

 curled posture, and by having a pair of respiratory tubes 

 on the dorsum of the thorax (Fig. 2). The pupae are 



Fig. 2. — Pupa of mosquito. The rwo respiratory tubes are 

 visible in the upper left part of drawing. ( After King, Bradley, 

 & McNeel 1939.) 



not diagnosed in this report. A larva of the Culicidae 

 can be differentiated from other aquatic, free-swimming 

 insect larvae by the following combination of charac- 

 ters: (1) legs absent; (2) head large and possessing a 

 hard covering; (3) thorax large and wider than the 

 abdomen; (4) the respiratory system opening dorsally 

 on the next-to-last segment of the abdomen; (5) four 

 blade-like "gills" extending posteriorly from end of last 

 abdominal segment (Fig. 125, 126). In many species, 

 the larva has a long or stout, usually hard and dark, air 

 tube (Fig. 125). Eggs of mosquitoes are black or gray 

 in color, sausage-like or spindle-like in shape, and each 

 not more than 1 mm long. 



Meinbers of the family Culicidae are frequently con- 

 fused with midges of the closely related family Chao- 

 boridae. In the Chaoboridae, no adult has a proboscis 

 and neither male nor female bites. In the Culicidae, 

 the adult has a proboscis; the male does not bite but 

 sucks up nectar and free water; the female sucks either 

 juices of plants or blood of vertebrates through a group 

 of fine, slender stylets housed within the proboscis. The 

 adults and larvae of these two families can be recognized 

 by use of the following keys. 



KEY TO CULICIDAE AND CHAOBORIDAE 



Adults (Both Sexes) 



Head having an elongate proboscis (Fig. 1, 6) many 



times as long as diameter of head Culicidae 



Head with no proboscis, mouthparts forming only short 



fleshy lobes that are no longer than depth ot head . . . 



Chaobaridae 



