27 
Persistent search for anopheline eggs, larvae, and pupae which 
might have hibernated proved fruitless. 
The conclusion is drawn that, in this region in northwestern Mis¬ 
sissippi, only the adult female mosquito of Anopheles hibernated. 
Collateral studies made in Alabama gave similar results. 
Hibernation data to be of intrinsic value must insure absence of 
fresh emergences and consider only the presence of the brood known 
to have emerged prior to the onset of the cold weather. The char¬ 
acteristics of the hibernating mosquito are indicated by the presence 
of eggs and abundant stored fat cells in the body of the old female, 
and by the entire absence of male anophelines. It is concluded that 
the appearance of male anophelines indicates recent emergences, and 
is interpreted to indicate the arrival of the spring brood. 
A control of field observations concerning laying of eggs during 
winter was provided by laboratory experiments with Anopheles 
quadrirnaculatus. These laboratory tests gave the information that, 
with more than 100 apparently gravid females, egg deposition did 
not take place at temperatures between 4.5° C. and 12.5° C. 
In another laboratory experiment, eggs were laid at temperatures 
ranging between 13.5° C. and 16.7° C., but these did not hatch except 
at temperatures above 16° C.; the optimum established being at tem¬ 
peratures between 19° C. and 21° C. These experimental data, 
applied to conditions found to exist in the region studied, would 
provide for egg deposition and hatching beginning April 21, when 
a mean temperature of over 16° C. was sustained. This fits in per¬ 
fectly with an experimental case in which a hibernating female 
Anopheles , caught April 10, 1915, was induced to bite and laid eggs 
April 16, which hatched April 21. 
Hibernation conditions were observed in January, 1916, in the 
State of Alabama at a point having the same latitude as Bolivar 
County, Miss. Probably the conditions found here are more rep¬ 
resentative for the southern United States. Stables in which cattle 
and horses were housed for the winter yielded more resting anophe¬ 
lines than elsewhere. A total of 371 specimens of Anopheles was 
collected here and, upon dissection, was found negative for malaria 
parasites. 
It was ascertained, during the course of the winter studies in the 
region investigated, that occasional biting of roused hibernating 
Anopheles did not have any pathogenic significance, and all of the 
clinical malarial infections occurring in this region during this period 
were proved to be recurrences of former attacks. 
It was concluded that hibernating anophelines, collected in the 
region investigated, did not harbor parasites of malaria. This was 
determined after an examination of 2,122 dissected anophelines, of 
which 1,211 specimens were examined before May 15, 1915. Among 
