SPIDERS AND MOSQUITOES 175 
larval hydrachnids can change their host, but that the mites are not especially 
harmful to the mosquitoes. In their rearings, larve, pups and adults most 
abundantly parasitized did not die any more frequently than unparasitized in- 
dividuals which they kept as checks. Doctor Trouessart informed them that he 
also believed that the well-known parasitization of aquatic insects in general by 
hydrachnids does not appear to be burdensome. 
SPIDERS. 
There is no doubt that many mosquitoes are destroyed by spiders. It is a 
matter of frequent observation to find mosquitoes in spider webs. Dr. H. C. 
McCook, a well-known writer on spiders, has written the following paragraph 
on this subject: 
“But do the spiders have a special taste for mosquitoes? it may be asked. 
They take what comes to them, and when mosquitoes are abundant mosquitoes 
are taken. I have counted in an orb weaver’s snare, spun upon the railing of the 
long bridge over Deal Lake, New Jersey, thirty-eight mosquitoes at one time 
hanging entangled upon the viscid spirals. Times without number have I seen 
like destruction wrought to mosquitoes by spiders’ webs; for it is a fact that, even 
after the aranead has satisfied its appetite, its snare continues to capture insects. 
On one occasion I took the pains to count the number of insects of various species 
upon one large web, which was spread in a favorable position, and found that 
there were two hundred and thirty-six. It is a most common thing to observe 
three, four, or half a dozen flies or other insects trussed up upon the viscid orb 
of some of our orbweaving species. It is needless to add the conclusion from 
the above facts : if people would decrease the number of mosquitoes, let them en- 
courage the multiplication of spiders.” 
The jumping spiders are probably more often an effective check upon the 
mosquitoes infesting houses than is generally realized. The commission of the 
Institute Pasteur, while engaged in their studies on yellow fever and the trans- 
mitting mosquito at Rio de Janeiro, found that their studies were seriously in- 
terfered with by spiders of the genus Salticus. They found that these jumping 
spiders were very common in houses in the tropics and that they are a valuable 
aid in the destruction of mosquitoes. In further praise of these spiders they 
state: “ Not only do they reduce the large number of mosquitoes, which enter 
the houses, in a noticeable manner, but the flies as well contribute largely to 
satisfy the appetite of these voracious jumping spiders.” It is probable that 
with us the mosquitoes which hibernate in cellars and similar situations are 
considerably reduced by the spiders which prowl about in these places. 
Doctor John B. Smith seems to be impressed by the number of mosquitoes that 
are destroyed by spiders. He states that he has frequently looked over a series of 
webs in the morning and found only mosquitoes captured. Sometimes there 
would be only one or two, and sometimes there would be a great bunch of them— 
reduced to little balls or dry husks. He considers it probable that many spiders 
subsist largely upon mosquitoes, and that they are among the most effective mos- 
quito checks. 
In a recent article Doctor N. Leon, of the University of Jassy, shows that in 
the marshes of the delta of the Danube, and in other localities in Roumania, 
