148 MOSQUITOES OF NORTH AMERICA 



An important fact to be considered is the habitat peculiar to each species or 

 group of species and this, of course, is intimately connected with the feeding 

 habits. Thus certain species are found only in rain puddles charged with mud. 

 Other species thrive in pools and ditches full of dead leaves and other vegetable 

 debris, or in sphagnum swamps. The Anopheles larvae are surface feeders and 

 often occur where there is a slight flow of clear water which favors the growth of 

 the algae upon which they feed. Some species of Anopheles thrive, however, in 

 other situations. We have found the larvae of certain species plentiful in tem- 

 porary rain puddles which showed no trace of algae. Other species of Anopheles 

 breed in the water in holes of trees and between the leaves of bromeliaceous 

 plants. Tree-holes form the habitat of the larvae of a number of species of mos- 

 quitoes which breed nowhere else. Plate x, fig. 3, shows such a mosquito breed- 

 ing tree-hole. Others, while strongly attached to tree-holes, show a certain 

 degree of adaptability, breeding in rock-pools, tubs and barrels under suitable 

 conditions. It is to be supposed that the food conditions along Avith the general 

 environment are here the determining factors. 



In the tropics the larvae of many species live in the water or liquid held by 

 various plants which are modified for this purpose. While this water or liquid 

 furnishes a breeding-place for mosquitoes and other insects it fulfills a more or 

 less important function in the economy of the plant. Thus in many Brome- 

 liaceae water collects at the bases of the leaves and this water serves as a barrier 

 to prevent the access of ants and other injurious insects to the flowers. With 

 certain tropical American species of Heliconia and Calathea the flower bracts 

 form a receptacle whose office is probably primarily to protect the flower itself. 

 In the case of Calathea at least the liquid held by the bracts is dark and thick 

 and is probably secreted by the plant itself. In America certain species of 

 Sarracenia and in the East Indies certain Nepenthes have leaves peculiarly 

 modified to hold liquid. These leaves act as traps to most insects, which, having 

 entered, can not escape and are finally drowned. Their decomposition is sup- 

 posed to furnish food for the plant. In our common pitcher plant {Sarracenia 

 purpurea) the leaf cups are open and have a broad lip to catch the rain-water 

 and dew. In the case of Nepenthes the leaf cup has a lid which projects over its 

 mouth and which, while it does not close it, prevents water from entering; the 

 cups are filled with a viscous liquid secreted by the plant itself. All these plants 

 support mosquitoes peculiar to themselves. In tropical America the many 

 species of the tribe Sabethini inhabit almost exclusively such plants. Certain 

 species of Culex are peculiar to the bromeliads, as are also a few species of 

 Anopheles and MegarMnus. Most of these larvae are scavengers and feed upon 

 the remains of insects that have been trapped by the plants. A few are pre- 

 daceous and prey upon the larvae of the other species. Such are Lesticocanipa 

 and certain species of Megarhinus. A remarkable fact is that even these canni- 

 balistic forms are confined to a single plant, each species of plant thus having 

 a fauna peculiar to itself. The only case in our temperate zone, of such close 

 adaptation to a single plant, is the pitcher-plant mosquito, Wyeomyia smithii. 

 Our plates iv, v and vi show water-bearing plants known to harbor mosquito 

 larvae and other aquatic insects in the American tropics. 



