87 



for a period of five days, and that any lower degree of relative livimidity 

 will cause the transmission of bird malaria to cease owing to the 

 premature death of the insect host. Relative humidity does not 

 appear to exert any direct influence on the degree of infection, or the 

 rate of development of the sexual parasite of l)ir(l malaria in the 

 mosquito. 



It was noticed that the mosquitos did not feed when the daily mean 

 humidity was less than 40 per cent., and fed readily when it was o\'er 

 50 per cent. Again, it was the custom to clear the house of mosquitos 

 in the evening by lighting the verandah and darkening the rooms, 

 when the insects would stream out, but on one particular night which 

 was hot, dry and windless, the usual procedure was reversed — no mos- 

 quitos attempted to go out, while numbers began to enter the house. 



Temperature exerts a direct effect on the malaria parasite in the 

 mosquito, low temperature inhil)iting the growth of the oocyst, while 

 its rate of development is dependent upon the mean temperature. 

 C.fatigans can live at a wide range of tempcrntun\ but at low tempera- 

 tures its vital functions are restricted. 



With regard to malaria in general, it is probable that the factors 

 of relative humidity and temperature require to be somewhat delicately 

 adjusted in order that a period of potential infection may occur. Thus 

 a rise in mean temperature, which otherwise might be favourable to 

 the transmission of malaria, may occasion a fall in relative humidity 

 which will cause the cessation of infection. Similarly a fall in mean 

 temperature, in spite of a concomitant rise in relative humidity, may 

 have a like effect. 



These considerations may explain the occurrence in a locality of 

 numerous Anophelines and many human carriers together with a 

 complete absence of new infections ; or the occurrence of new infections 

 in localities where Anophelines and human carriers are relatively 

 few. 



A point of immediate practical importance is that, with a knowledge 

 of the lower limit of temperature and humidity necessary to create a 

 period of potential infection, it is possible in the case of any area for 

 which the necessary meteorological data are available, to determine 

 the season of the year and the precise duration of the period during 

 which malaria may be acquired. 



Mackenzie (F.). Sheep-Management Notes. — N. Z. J I. Ai^nc, 

 Wellington, xxii, no. 1, 20th January 1921, pp. 41-42. 



The importance of dipping sheep is emphasised, and llic jMecautions 

 necessary for successfully carrying out the operation are dealt wilh. 



DvAK (H. G.). A new Mosquito from East Africa (Diptera, Culicidae). — 



Insecutor Insciliac Mcnslnitts, Washijit^lun, D.C., ix, nos. 4-6, 

 April-June [issued 28th Feb.] 1921, pp. 51-52, 1 fig. 



Aedes {Ecculex) rhecter, sp. n., is described from Portuguese East 

 Africa. 



DvAK (H. G). The American Aedes of the fynnv/or Group (Diptera, 



Culicidae). — Insccnlor Insciiiae Menstnius, Washington, D.C. ix, 

 no. 4-6, April-June [issued 28th Feb.] 1921, pp. 69-80, 1 plate. 



The author proposes to substitute the subgeneric name Ochlerotatus 

 for the group of Aedes treated by him as Heteronycha [R.A.E,, B, ix, 9] 



