MOSQUITO DIAGNOSIS. 247 



MOSQUITO DIAGNOSIS: A SUGGESTION TO DESCRIBE 

 WING-SPOTS, FORK-CELLS AND PALP-MARKINGS BY 

 MEANS OF WRITTEN FORMULA. 



By Gilbert E. Brooke, M.A.Cantab., L.R.C.P.Edin., D.P.H., 



Chief Health Officer, S.S. Medical Dept. 



In describing a mosquito for a book or paper nearly every 

 detail can be adequately set forth in words without the aid of 

 diagrams or photographs. The various shapes of scales are now 

 well recognised and need only be referred to in zoological parlance. 

 The mosquito can be measured and its actual size given. The 

 position, colour and size of abdominal or leg-banding can be expressed 

 in words without ambiguity. 



There are three details, however, which it has been almost 

 impossible up to the present to express in words, and recourse to 

 diagrammatic sketches or photographic reproduction has usually 

 been found necessary. I refer to (a) anopheline wing-spots ; 

 (/)) the relative length of the first submarginal and second posterior 

 fork-cells in culicine wings ; and (c) to the size and position of ano- 

 pheline palpar banding. In working out diagnostic tables for the 

 use of my department, I felt that if these details could be reduced 

 to writing it would mean not only the saving of much expense in 

 the reproduction of illustrations, but also greater scientific accuracy. 

 Hence the formula? presently to be described, which are now pub- 

 lished in the hope that they will prove useful to entomologists. 



Wixg-Spots. 



For all practical diagnostic purposes, with regard to wing-spots, 

 we are only concerned with those which occur on the costal, the 

 subcostal and the first longitudinal veins. These may be black 

 spots in a dominantly light wing, or white spots in ;i dominantly 

 dark wing. 



The wing formula is arrived at in the following way : Tin 

 costa, from a basal point opposite to the axillary notch, as far 

 as its junction with the first longitudinal vein, is arbitrarily divided 

 into 25 equal parts. To each of these parts a letter of the alphabel 

 (omitting " i ") is assigned, beginning from the basal point. 1 1 

 black spots are being described we begin the formula with ' B 

 = so and so" ; if white spots are being described, we begin with 

 "W = so and so." The costal spots are described first, each 

 spot being designated by the alphabetical letter or letters of tin- 

 one or more sections which it occupies. A caesura is used to punc- 

 tuate the spots, and the conclusion of the costal pari of the formula 

 is marked by a double caesura. The formula then proceeds with 

 the literal designation of the spots ,>n the subcostal vein, similarly 



