1913] Determining the Flight of Mosquitos 15 



first is a 1 : 20 aqueous solution of phenolphthalein. It was 

 found satisfactory on typhoid flies and is detected readily when 

 a drop or two of one percent solution of ammonium or sodium 

 hydroxide is added to the suspected specimen. A deep red 

 color indicates presence of the drug. The second agent is 

 corn starch and it is detected by applying tincture of iodin, a 

 purple color ensuing in its presence. We had no opportunity 

 to give this latter method a fair trial. 



B. Staining the Adults: The mosquitos in the rectangular 

 screen cages should be stained preferably toward evening, 

 about two hours before they are to be released, and always at 

 the station where they will be liberated. A shelter must be 

 provided for these cages. The stains must be applied lightly 

 and must be dry on the insects before they may be allowed 

 freedom. Small globules of water on the wings weight these 

 down to such an extent that the mosquito cannot fly, and it is 

 then easily captured by ants, roaches or more alert forms. 



The aqueous solution of the anilin dyes is converted unto 

 a very fine spray through a vaseline-nebulizer, or a fine atom- 

 izer, and this spray is allowed to fall upon the mosquitos. 

 Direct and forceful projection of the stain against the sides of 

 the mosquito is productive only of death to the insects. Too 

 concentrated solutions must be avoided. The idea is not to 

 encrust the mosquito with the stain, but to place a minute speck 

 only upon the body. Hundreds of tests, using mere specks of 

 the stain gave perfect results when tested for color. The 

 danger of too-protracted a staining is that spiracles become 

 sealed with the stain, mouth parts glued together, sensory 

 areas covered, wings folded, etc. ; in other words the mosquitos 

 are no good. 



After the mosquitos have been liberated, the cage should be 

 washed in clear water to dissolve all superfiuous stain adhering 

 to the screening or sides of the cage. Such crusts, if allowed to 

 remain, create a foulness about the cage which is detrimental to 

 the mosquitos confined therein. It is best, though the statement 

 seems hardly necessary, to keep separate cages for each color 

 used. 



To remove stains from fingers and hands, received during 

 the coloring operations, wash hands in acid alcohol. The best 

 way is to use rubber post-mortum gloves when staining 

 mosquitos. 



