182 MOSQUITOES OF NORTH AMERICA 
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 larvee 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 te 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 with 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 skins 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 larve 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 larve 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 larve 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 Culex 
restuans, which live in foul water containing decaying organic matter, fed 
pieces of meat to larve of Wyecomyia smithit, that live in water in pitcher- 
plant leaves, and the resulting fermentation killed them all. Some mosquito 
larvee are cannibalistic and must be supplied with the larve 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 
grown larve, which will generally successfully complete their transformations 
upon the food material collected with them. It must not, however, be forgotten 
