SPIDERS AND MOSQUITOES 175 



larval hydrachnids can change their host, but that the mites are not especially 

 harmful to the mosquitoes. In their rearings, larvae, pup^e 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 orbwea\'ing 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 Eio 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, 



