166 1.S.C. Proceedings of the Ninth [N.S., XVIII, 
I s on these pours thought expedient, in connexion with the 
study of epidemic malaria in the Punjab, to investigate the precise ahiat 
of meteorological co sodinons on the Vife- -history of mosquitoes and o 
their 2 tei to transmit infection. 
need not detail the experiments undertaken with this object in view 
since ee ey are described in the April number of the Indian Journal of 
Medical Research, but I must refer briefly to some of the conclusions to 

which they gave ris 
Tt was found that susceptible to the influ- 
2 of humidity and that their length of amp was largely determined by 
the relative humidity of the atmosphere. : the f Cu 
fatigans, when adults are incubated at a relative humidity of 45 per cent 
or less (at a constant temperature of 27°C) they die within 5 days, whilst 
‘* controls’’ incubated under ee oe ns but at a relative humi: 
dity of 48 per cent or over alm invaria ur at 
days. Insects have in fast ag teas: alive in the laboratory under 
months. conditions of temperature and  Haidiey for near we two 
ont 
the atite of — — as ei selection of resting plane duing the 
heat of are , by oi controlled experiments, 
that at low we ingtses of relative “humidity egg-developmen f eC 
females was retarde nally igh degree a relative humidity was 
found to be an wapeetant Since in determining the desire of mos 
tte hes feed on blood. 
her wei’ of ex osama pene with Culex fatigans infect- 
ed wah pith a (Proteosoma grassi) showed that batches of nee 
ie roe ‘nti al — ons ‘ead | incubated at the ae poor ee 
e nt de 
t of odcysts d ornare in the mid-gut. It was also 
that the shortest period bisiiieied for the eT of the devolancetie 
al ne e of ce parasite e in the mosquito was six day. 
sh kar therefore bt to the plow that, whilst re- 
— bisa ty may e e an important influence in deter minted 
pepcciser ae n of malar a bps reason of its effect on the longevity o 
quitoes, it does not vere any direct offect on the malaria parasite soc 
its exogenous cycle. 
On the other more b ations on — influence of temperatur> 5 show 
that low temperat e (in the pre f high relative humidity) has 
little effect on the aoiiagtl of life of ese although low tem sire a 
as in hibernation, —— — penne vital functions. But tem- 
perature exerts influe 4 larial pee since 
opme 

hilst 
directly with the height of the temperature above this figur 
hese obser neath therefore suggest that the siesta factors of 
temperature and humidity are both capable, ape - a different ™' 
a ission of malari se 
= elements are ne wine perio in Nature Scoot marked rise 19 
mperature is usually associated with a onc coalee in atmos 
nee humidity and ote ver 
A fall in sien tem ceesie may thus give rise to atmosphere oe 
tions favourable to the prolonged life of mosquitoes but ico mpatible 
with the transmission of — —_ to an unfavourable tempera 
On the other hand when the mean temperature undergoes @ ™ 
rise the relative humidity i is = apt to “fall 0 the ‘‘ critical ’’ figure. 
such circumstances mosqui s may be prevalent a d active - ~ 
transmission of eualavia sire remain in prenen e since infected 1! 
will not live long enough to transmit infec i Pace 
These facts, I think, pine to the pana that — 1 
