NATURAL ENEMIES. 
The subject of the practical use of natural enemies of mosquitoes is considered 
in the section of “ Remedies.” As virtually the only natural enemies of mos- 
quitoes which can be used practically are fish, a rather full consideration of fish 
will be found in that portion of this work, and is omitted in this present treat- 
ment. 
PLANTS. 
At least two groups of herbaceous plants contain mosquito destroyers. The 
bladderworts (Lentibulariacee) of the genus Utricularia, living in water, have 
little bladders which trap small aquatic animals. The bladders have each a 
valve-like door through which the animals enter when looking for food or when 
trying to escape from their natural enemies. Darwin, in his work on insectiv- 
orous plants, cites observations made by Mrs. Treat in New Jersey with Utric- 
ularia clandestina. It was found that larve, probably those of mosquitoes, 
when “ feeding near the entrance, are pretty certain to run their heads into the 
net, whence there is no retreat. . . .” Fully nine out of every ten bladders con- 
tained these larve or their remains. The species which grow in stagnant waters 
have the most effective bladders. Mosquito larve inhabiting stagnant pools in 
which the Utricularia grows are quite often entrapped in this way. 
Recently J. H. Hart has kept under observation a species of Utricularia which 
occurs in pools at the Pitch Lake in the island of Trinidad. He found dead 
mosquito larve in the bladders and also newly caught ones struggling for free- 
dom which afterwards succumbed. Eysell gives photographic reproductions of 
Utricularia with mosquito larve in the bladders. 
Ernst Krause * has called attention to the presence of Utricularia, in Brazil, 
in the water accumulations between the bases of the leaves of bromeliaceous 
plants, and as these water accumulations have since been shown to be fertile 
breeding-places for certain species of mosquitoes, it is very probable that the 
Utricularia here exercises a certain degree of mosquito control. 
Another Brazilian bladderwort, Genlisea ornata, is said by Dr. Adolf Eysell 
to capture mosquito larvae. He compares the tubular leaves of this plant to an 
eel-trap. 
According to the same author a member of the sundew family (Droseracee), 
which grows submerged, captures mosquito larve. This is the Aldrovanda 
vesiculosa of southern Europe and the adjacent warm countries, the leaves of 
which have a structure and function similar to that of the well-known Venus’s 
fly-trap (Dionea muscipula), its leaves closing quickly upon any insect that 
touches them. 
* Die Schutzmittel der Bltithen gegen unberufene Giste (Kosmos, 1887, vol. 1, p. 80). 
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