VII 



Natural Enemies of Mosquitoes 



WHEKE mosquitoes exist in rain-water buckets 

 and barrels they are apt to have none or very few 

 natural enemies. Their jDrincipal enemies when 

 in the aquatic larval and pupal stages are fishes and carniv- 

 orous insects. Most carnivorous insects are rather slow 

 breeders, and as a consequence they seldom deposit their 

 egg-s except in rather permanent pools, and naturally 

 fish are found only in such places. There are, however, 

 other enemies aside from these. Dr. C. W. Stiles informs 

 me that during the summer of 1889, when working with 

 C. H. Hurst, they collected at Leipsic a large number of 

 mosquito larv&e and i^upae, and that many of them died in 

 the laboratory. Upon opening one of the bodies, which 

 was quite distended, he found a species of Mermis, one of 

 the hair worms or hair snakes, coiled up in the body cav- 

 ity. Examination of other dead larvae or pupfe disclosed 

 the fact that nearly every one was parasitized by the same 

 species of Mermis. He showed the worms to Professor 

 Rudolph Leuckart, who informed him that he had re- 

 peatedly found the same Nematode in former years, and 

 that he had observed that in years when mosquitoes were 

 numerous the worm is very scarce. This led him to be- 



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