NATURAL ENEMIES OF MOSQUITOES 157 



lieve that the parasite was a not unimportant factor in 

 destroying- mosquitoes near Leipsic. Later, Dr. Htiles 

 found the same worm in mosquito larvie and pu})* taken 

 from other breeding'-phices, and it was quite noticeable 

 that the iJarasitized insects were weaker in their move- 

 ments than those tliat were not infected with the Avorm. 

 In the next summer (181)U) he again looked for the worm, 

 but found none, and it appeared to him that mosquitoes 

 were more abundant that year than in 1889. 



Dr. Stiles also informs me that a Sporozoan of the 

 genus Glug-ea is referred to as parasitic in mosquitoes, but 

 that Labbe, in his recent monograph of the Sporozoa, 

 does not give Culex in his list of hosts. Dr. Stiles does 

 not recall who found this parasite, nor does he know 

 whether it is of any particular economic importance. 



By far the most effective natural enemies of mosquito 

 larvae and pupae are fish. Almost all of the small carni- 

 vorous fish which inhabit swamp pools and still water 

 will feed upon mosquito larvae. Nearly all of the minnows, 

 especially those forms knowni as top-minnows, of the gen- 

 era Fundulus and Gambusia, feed abundantly upon in- 

 sects found near the surface of canals, slow streams, mill- 

 ponds, and other similar places, and, although not at all 

 specific in their choice of the early stages of the mosqui- 

 toes, eat them perhaps with even more avidity than other 

 aquatic insects, especially such as are hard-shelled. 

 Then, too, the voracious little creatures known as stickle- 

 backs, and especially the forms known as Gasterosieus acv- 

 leai)i.siiW(\ G. hisphiosii.^ hav(^ this beneficial habit. Stickle- 

 backs, however, are by no means confined to insects for 



