140 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



buildings for the presence of mosquitoes and are very useful, especially 

 upon overcast days and in poorly lighted native houses. The fumiga- 

 tion of buildings for the destruction of Anopheles mosquitoes is not 

 now often practiced and is resorted to only in rare cases of excessive 

 infestation and malarial infection. 



The natural checks to mosquito propagation, which are often 

 effective in northern countries, fail as an important aid to control 

 work where plant life is so exuberant and the multiplication of mos- 

 quitoes so prolific and persistent as is the case in Panama. Small 

 fishes of many species, including several of Gambusia, are very abundant 

 and occur in the smallest brooks and open ditches. Though they 

 destroy many larvae, they cannot effect the eradication which is essen- 

 tial to the work and must be disregarded, together with predaceous 

 aquatic insects. 



Special and exceptional problems are being constantly presented, 

 due in many instances to the engineering work connected with canal 

 construction. Swamps of large area are sometimes unavoidably 

 created and before drainage can be effected, breeding of Anopheles 

 has assumed formidable proportions. The gravity of the situation 

 is also, often increased by the difficulty of applying control measures. 

 In some instances boats of shallow draft have been employed to carry 

 powerful force pumps capable of throwing oil many feet, the crew 

 being armed with axes and machetes to cut away tangled undergrowth. 

 Hydraulic fills, formed of the material from suction dredges spreads 

 over low-lying areas, are among the most serious and difficult situations 

 to control. Breeding is active, especially as the water drains away 

 and evaporates, while the soft mud, often with a deceptive crust upon 

 it, offers an almost insuperable and often dangerous obstacle to 

 penetration of the area. Slides of earth and mud, developed in the 

 course of excavation, often cover areas many acres in extent and are 

 always prolific breeding places. Like the hydraulic fills, they are 

 difficult, and even more dangerous, to venture upon. 



The great Gatun lake, with its approximately two hundred square 

 miles of area and hundreds of miles of rugged shoreline, bids fair to 

 offer many problems as its level continues to rise. In the sheltered 

 bays and indentations of its shore line, aquatic vegetation riots, and, as 

 the waters inundate the tropical forest, a condition is created, ideal for 

 the most prolific breeding of Anopheles and other mosquitoes; a 

 tangle of living and dead vegetation, with floating debris from the 

 dying trees, among which water plants flourish. A large part of the 

 breeding areas formed will probably affect only scattered habitations 

 and ranches but, wherever settlements and towns are contiguous 

 to the permanent shore line, correction of these conditions will be 



