THE MOSQUITOES OF THE SOUTHEASTERN STATES 



27 



Another difficult problem is encountered in certain areas where the 

 marshes border more or less landlocked bodies of water in which there 

 is ordinarily little tidal range. Strong wind tides may cause a flood- 

 ing of these marshes, and continuous winds may hold the water there 

 long enough for a brood of mosquitoes to develop even though the 

 marsh is thoroughly ditched. To meet this problem it has been pro- 

 posed to dike such areas and remove the floodwaters when necessary 

 by means of pumps. A program along this line, combining mosquito 

 and sand fly control, was begun in Saint Lucie County, Fla., in 1936. 



The control work against salt-marsh mosquitoes in the North 

 Atlantic States has been criticized as unnecessarily destroying the 

 feeding and breeding grounds of wildlife. It is believed that many 

 of the deeper ponds, as well as the plant species that serve as food, 



Figure 8.- 



-Red mangrove (Rhizophora mangle) in a Florida salt marsh, show- 

 ing the dense growth and characteristically divided base. 



can be saved without detriment to the antimosquito work. In the 

 case of ponds that are of value as feeding and resting grounds for 

 wild fowl, the ditches may be diverted or, if they are run into the 

 ponds, a sod dam or wooden spill gate may be inserted, somewhat 

 lower than the marsh level, to prevent complete drainage of the pond 

 and to permit the inflow of high tides. Deepening of the shallower 

 ponds may be necessary to obtain surface drainage on the neighbor- 

 ing marsh and should greatly increase their value and permanence. 

 Experiments are also under way in the digging of artificial ponds in 

 ditched marshes. 



Another problem arises in connection with the lowering of the 

 water table, which results sometimes in an undesirable change in 

 plant species and sometimes in a subsidence of the marsh level. As 

 such changes vary greatly with different soil and tidal conditions, a 

 thorough study of such factors should be included in the original 

 surveys. Where the soil texture indicates little water-holding capac- 



