1915} Behavior of Anopheles 243 
K. ANOPHELES AND MALARIA, GATUN DISTRICT. 
Feb. 1 | Feb. 8 | Feb. 15 
PR AWEGA EC Mea Gr GUTS Wales nuiiee isc Goaieboe arcline serene: 1,039 604 387 
Trap and hand catch, both Gatun and New Gatun 12,067 11,897 12,838 
BIG treat renmree rae ea tae a at cy aha RP toy aRt del atone eben 13,106 12,501 13,225 
MalanianCases: Amenicam WialbeSss-sessci seis ee 5 + 8 
MiailantalGasessiGatunwaliltothiersas.a secs sae aes el 16 20 19 
Matlanciay Cases New: Garttnes ss encecrs a sis citoets chara 3l 33 39 
By trap catch is meant those mosquitos which were caught 
in the ‘‘C. H. Bath’’ mosquito traps attached to barracks, and 
hand catch refers to mosquitos caught by expert negroes 
within buildings, by means of a small killing vial. All counts 
were made daily. 
Though the white American is presumed to be more sus- 
ceptible to infection, his well-screened home, his rather regular 
habits, and the free use he makes of the dispensaries, protect 
him amply against ready infection. The cases reported are 
mostly of men working on night shifts. Negroes and Spaniards 
show more malaria, due largely to habitual loungings outdoors 
after dusk, thus exposing themselves to Anopheles bites. The 
New Gatun high percentage is due to lack of screening (Oren- 
stein, 1912-b). The New Gatun cases, as well as those of 
negroes in Gatun proper, are only such as presented themselves 
at the dispensary, and often malaria was a secondary diagnosis, 
for the patient complained of totally different symptoms. It 
is the general rule that the first attack of malaria gives the 
negro considerable fever, whereas subsequent attacks are much 
milder. Very often a negro may havea good quantity of 
parasites roaming about in his blood, yet be unconscious of 
the fact. Such cases do not find their way into the dispen- 
saries, and of course are among our worst enemies, for they 
allow the spread of the fever. Therefore it may be reasonably 
supposed that the malarial rate in New Gatun was at least 
fifty per cent. higher than reported. 
The narrowness of the strip of the Canal Zone, its congested 
labor centers, frequent trains and heavy traffic, added a big 
factor, that of the spreading of Anopheles from this place to 
