RELATION OF ARTHROPODS TO PATHOLOGY—MAROTREL. 121 
what has been done against mosquitoes. In order to develop, these 
dipterous insects have absolute need of still, stagnant water. It is 
on the surface of these waters that the females lay their eggs and 
that the larvee and nymphs live. The presence of quiet waters, such 
as lakes, swamps, ponds, pools, or puddles is necessary for the evolu- 
tion of the Culicids: and this necessity is felt by them all. Thus, it is 
well known that there are certain towns which have an abundance of 
water have also the doubtful advantage of being literally overrun 
by mosquitoes so that they are rendered almost uninhabitable. This 
is the case with Venice, Mantua, and Livourne. It is also well 
known that at Majunga, Madagascar, for example, which lacks fresh 
water, there are few mosquitoes and the place is very healthy. 
Nossy-Bé, on the contrary, possesses an abundance of fresh water and 
beautiful, luxuriant vegetation, but also an abundance of mosquitoes 
and constant malaria. It is also, for the same reason that in our 
great African island the presence of rice plantations causes a recur- 
rence of fever. Soon after the rice is cut these plantations are 
flooded with stagnant water intended to hasten the decomposition 
of the roots. The whole region is then transformed into a veritable 
putrid marsh, very favorable to the development of mosquitoes. The 
_insalubrity of rice culture has always been recognized and it is this 
which caused Vivarelli to say, “the rice plantations produce two 
things—rice and fever. The crop of rice may be deficient, but that 
of fever is always abundant.” 
Consequently, there is no doubt that the presence of standing 
water is indispensable to the development of mosquitoes, and it is 
no longer doubtful that in principle the exclusion of such waters 
results in the suppression of Culicide. This suppression is possible 
in a number of cases in which ponds, pools, wells, and reservoirs are 
unnecessary. When it is not possible because the reservoirs are neces- 
sary, the mosquitoes can still be destroyed by a simple process. It 
suflices to pour a little kerosene on the water, This substance kills 
the larvee and nymphs as they come to the surface for respiration, 
The two measures which we have mentioned, the suppression of the 
stagnant waters and the use of kerosene, cause the extermination of 
the mosquitoes. They should be supplemented by a third, the pro- 
tection of individuals against the bites of those that remain. 
The Culicide are nocturnal insects which conceal themselves during 
the day and fly only after sunset. It is only necessary, then, to pro- 
tect one’s self against them during the night. This protection can be 
obtained mechanically by closing the openings of houses by means 
of metal screens sufficiently fine to exclude the insects, by covering 
the face by an ample veil attached to the hat, and by covering the 
hands with thick gloves. Wherever this triple means of protection 
is used thoroughly, the diseases caused by mosquitoes have disap- 
