182 MOSQUITOES OF NORTH AMEEICA 



original liquor and the cotton stopper inserted. As any given culture is apt to 

 contain a mixture of species, it is well to use care to select those larvae that appear 

 to be of different kinds. A culture may contain hundreds or thousands of in- 

 dividuals, and it is seldom feasible to isolate them all. The rest may be bred in 

 common to secure a supply of adults; but the jar should be kept under daily 

 observation to see if any different species at first unnoticed appear. 



The isolation made, each individual should be given a double number, one for 

 the original entire culture as reference to the notes of locality and date, the 

 other a serial number for the identification of the individual isolation. These 

 numbers should be attached to the tube so that they are not liable to get mixed. 

 All the isolations should be viewed at least once a day, and as soon as the larva 

 has pupated the cast skin should be removed with a pipette and put in a small 

 vial with alcohol containing a little glycerine and stoppered with cork, A small 

 label bearing the locality and isolation numbers should be inserted in the bottle, 

 and the bottle kept vrith. the isolation until the adult has emerged. On the is- 

 suance of the adult, the pupa skin may be added to the same bottle. Finally, 

 the small bottles of slcins should be stored in a larger jar containing alcohol, to 

 keep them from drying. 



The adult should rest at least twenty-four hours after emergence for its chitin 

 to harden and become perfectly dried. If killed too soon the specimens will 

 shrink and collapse and be rendered unfit for study. When sufficiently hardened, 

 the mosquito can be removed, killed by chloroform, mounted and given the 

 locality and isolation numbers in addition to the usual data of locality, date and 

 collector. The locality note-book should be kept as fully as possible, giving not 

 only locality and date, but the character of the water in which the larvae occurred 

 and in what it was retained. There is no danger of recording too many data ; 

 the recording of too few is a common failing. 



The food of mosquito larvas consists of the organic matter in suspension in 

 the water, or floating upon the surface, or settled or growing upon the bottom. 

 It varies with the different species, so that the safest rule for general use is to 

 keep a supply of the original water together with the detritus at the bottom and 

 change the water in the isolation tubes occasionally. Experience will often 

 show the nature of the food of a given species, and in such cases artificial food 

 can be supplied, on which the larvse will thrive even better than in their natural 

 environment; but such an experiment may have a fatal termination. Doctor 

 John B. Smith, who was familiar with the habits of Culex pipiens and Gulex 

 rcstuans, which live in foul water containing decaying organic matter, fed 

 pieces of meat to larv^ of Wyeomyia smithii, that live in water in pitcher- 

 plant leaves, and the resulting fermentation killed them all. Some mosquito 

 larvae are cannibalistic and must be supplied with the larvas of other species for 

 food, preferably of the same species with which they were found associated. No 

 general rules can be given, as each species is a law unto itself ; but the collector 

 who desires the quickest results will isolate the largest, or most nearly fully 

 grovm larvae, which will generally successfully complete their transformations 

 upon the food material collected with them. It must not, however, be forgotten 



