364 MOSQUITOES OF NORTH AMERICA 
cage was divided across by a double partition consisting of 2 pieces of 16 mesh 
gauze separated by a space 2 centimeters wide. Each compartment was pro- 
vided with an opening for the hand. 
“ The experiments were made exclusively with the stegomyia mosquito. They 
were commenced on the Ist of June of this year. 
“ On the 1st of June, 100 stegomyias, male and female, were let loose in the 
large cage where they found dry food (sugar), but no water. In the cage was 
placed the tub, three-quarters filled with rain water, and closed with 16 mesh 
gauze. After six days all the mosquitoes in the cage had perished, evidently for 
want of water. No mosquitoes had passed the 16 mesh gauze. No eggs were 
found in the water, and no larve developed there. 
“On July 4th, 200 stegomyia mosquitoes, male and female, were let loose in 
the same cage. On the 9th there were only two insects left alive. On the 10th 
these two were dead. No mosquitoes, eggs or larve were found within the tub 
or in the water. This experiment was, in every respect, a repetition of the first. 
“Tn the small cage the experiment was four times tried of placing three 
unfecundated females on one side, and three males on the other. Both groups 
were provided with food and water, and the females were occasionally allowed 
to bite. These females had been obtained from pup that had been kept iso- 
lated, each one in separate bottles, so that all possible contact with the male 
could be excluded. The double partition in the cage prevented the possibility 
of contact through the partition. The males and females never passed through 
the partition and the females were not fecundated. 
“The experiment was also repeatedly tried of keeping males and females 
together on one side of the partition, and food and water on the other side. 
Banana, sugar, molasses were tried separately. At times also the hand was kept 
in the empty compartment for periods of from 30 to 40 minutes. If no water 
was allowed on the side occupied by the mosquitoes they promptly died. Other- 
wise they endured long, but were never able to pass across, nor could we ever 
see any evidences that they made any attempt to push themselves across. 
“ Another series of experiments were made by darkening one side of the cage 
with a dark cloth. The mosquitoes were placed sometimes on the dark side, and 
sometimes on the uncovered or light side. These insects were allowed food and 
water during the experiment. They never passed through the partition. 
“It is my opinion that we may conclude from these experiments that the 
stegomyia calopus can not pass through the wire gauze sent for trial. The gauze 
is a 16 wire mesh; that is, it presents 16 wires or threads to the linear inch.” 
Dr. Samuel T. Darling, Chief of Laboratory of the Board of Health, Depart- 
ment of Sanitation, Isthmian Canal Commission, in a paper entitled “ Studies 
in Relation to Malaria,” Washington, Government Printing Office, 1910, gives 
the results of certain observations upon the size of mesh of wire screen. He finds 
that at the Isthmus a 16-mesh screening answers the purpose against malarial 
mosquitoes, but that against the yellow-fever mosquito, while practically safe, 
it is not absolutely so. Out of several hundred mosquitoes, 8 species were able 
to make their escape through a 16-mesh screen, as follows: 
; Hamer of 
Stegomyia calopus: “beaaped.- 
IMEC: cites ab facchitisdes Scie aparelatecd seve Vasari aon vow wiaaeraheadeioiewe- eases 10 
POM AIESY sz. sissies voce: av gua vnews <geaite up atten’ cea cavanate Ea Gist eae 6 
Culem cubensis, Male. ..... ccc cece eevee eccseceneence sae 
Culex rejector, Male. iod5c4 sone cas UawW se NOR 4s sXe ea NaS 8 BES 1 
Oulex extricator, female. ....... ccc cece cece cere e eect ences 1 
Aedes angustivittatus, female... .. ccc ccc cece cece eee eeeeees 1 
Uranotenia lowti, female... ..... ccc ccc ee eee eee cece eens 1” 
