2 16 
would be of considerable value for this purpose, and would continue 
to be efficient until washed or drained out and that copper sulphate 
is a valuable algacidal agent for the destruction of filamentous 
algae, as Spiro gym. 
In experiments with the coal tar larvacide in laboratory tanks and 
under actual conditions the coal tar larvacide was found destructive 
to grass in dilutions of io per cent., the grass turning brown in two 
or three days and drying in five to six days. When Spiro gym was 
treated with the larvacide, dilutions of r to 2,500 were sufficient to 
kill, while dilutions of 1 to 5,000 and 1 to 10,000 greatly reduced 
its vigour. 
COMPOSITION AND SIZE OF MESH OF WIRE SCREENING 
Two extremely important factors in the use of wire screening for 
protection against mosquitos, are, first, the size of the mesh, and 
secondly, the chemical composition of the wire used. In regions 
where it is only necessary' or desirable to protect against 
Anophelines, a No. 16 mesh screening (sixteen holes to the inclii 
would answer the purpose, and where, as in this region, it is 
necessary to protect against some of the smaller species, such as 
Stegomyia cal opus, a No. 16 mesh would be practically safe, but 
not absolutely so. The following experiments were conducted to 
determine the varieties of mosquitos which would, under stress of 
circumstances, pass through a No. 16 mesh wire screening. Out of 
several hundred mosquitos eight common species were able to 
make their escape through a No. 16 mesh wire. 
Sex 
No. of specimens escaped 
Stegomyia calopus . 
Males 
10 
» ... 
Culex cubensis . 
Females 
Male 
6 
I 
„ rejector . 
„ ex trie a tor ... 
Male 
1 
Aedes angustidittatus 
Female 
! 
Uranotaenia lotcii ... 
Female 
Female 
I 
I 
No specimens of Ce. albirnana or A. pseudopunctipennis escape 
through No. 16 wire mesh screen, although several hundred were 
Tied. The methods adopted were as follows: — 
