STRUCTURE, CLASSIFICATION, AND KEYS 9 



mens that have been on the wing seven or eight weeks, the really charac- 

 teristic marks disappear, and determination becomes difficult, if not 

 impossible. Regardless of the period in adult life when the mosquito is 

 caught for classification purposes, it should always be placed, without 

 touching with the hand, in a cyanide jar or other gas killing apparatus. 

 As soon as dead it should be emptied on a layer of very loose cotton. Un- 

 less it can be pinned within twenty-four hours it should be placed in a 

 relaxing box (moist chamber humidor). When ready it should be laid 

 on a smooth surface and pinned through the side of the thorax, a 

 method which the writer prefers, because absolutely no handling of the 

 specimen is required. The common method is to thrust the pin through 

 the thorax from top to bottom. By use of a spacer the insect should be 

 slipped up the pin until thumb and finger can grasp the head without 

 touching any part of the insect. The date and locality label should then 

 be slipped up the pin to a point in clear view. The completed specimen 

 is then thrust into the cork bottom of a tight box furnished with naph- 

 thalene to protect the mosquito against museum pests. In this way mos- 

 quito specimens may be preserved indefinitely. If storage is not desired 

 the preparation may be stopped with the pinning. 



Larval mosquitoes can be classified with certainty only as they are 

 prepared for use under the microscope, or each individual separated 

 out and allowed to breed through to an adult. In the field, larvae may 

 be scooped up with a dipper, and placed in vials filled with eighty per 

 cent alcohol. In this way they will remain in condition for study for a 

 long period. At any time specimens may be removed and mounted on a 

 glass slide for study. Of course, still better conditions may be obtained 

 by bringing the larvae in alive and dropping them into hot absolute al- 

 cohol. After giving time for the alcohol to remove the water in their 

 bodies (ten minutes when the number of specimens is small, and the vol- 

 ume of alcohol large) they should be placed in xylol for clearing. When 

 sufficiently clear they may be mounted directly on slides in Canada bal- 

 sam. When properly carried out, this process gives specimens that will 

 last indefinitely. 



The mosquito's body, like that of most insects, is made up of three 

 distinct regions — head, thorax, and abdomen. The head is a globular 

 object having: a pair of eyes, one on each side; a pair of more (male) 

 or less (female) feathery feelers, antennae; a pair of mouth feelers, or 

 palpi; and a long prominent beak. The thorax is wedge-shaped, broader 

 above than below, and bears three pairs of legs on its lower surface and 

 one pair of transparent wings on its upper surface. The upper surface 

 (dorsal aspect) of the thorax is elongate, elliptical, and is formed 



