44 PREVENTIVE AND REMEDIAL WORK AGAINST MOSQUITOES. 



breeding was possible. Undrained marshes presented a very different condition. 

 Mosquitoes swarming in adjacent woodlands made driving very uncomfortable, and 

 when on the marshes one was attended by considerable swarms of vicious biters, even 

 in midday. Here and there breeding pools were literally black with young wrigglers. 

 This contrast between drained and undrained areas would doubtless have been much 

 greater were it not for the fact that our inspection was made during such a dry time that 

 even undrained marshes presented comparatively few favorable breeding places. 



Experience at Lawrence has shown that deep ditches with perpendicular sides are 

 far more permanent than shallow ones with sloping sides. The attempt to slope the 

 bottom of the ditch so that all the water will drain out invariably results in depressions 

 which may become dangerous breeding places and the drainage value of the ditch is 

 much lessened. Sloping sides afford opportunity for the growth of grass and sedges 

 with the result that the ditch soon becomes choked with vegetation. The deep per- 

 pendicular ditches described above remain entirely free from vegetable growth, and 

 with a little care in removing sods and drifting matter will last ,for years. Some dug 

 four years ago were in perfect condition last July, though the grass growing along the 

 sides overhung and almost hid the ditch from view in places. An area of 25 feet on 

 each side is easily drained by such a ditch. The village now has 40 miles of marsh 

 drains, which require more or less attention from three men during most of the open 

 season. They keep the ditches clear, supplementing their work by judicious oiling 

 here and there wherever mosquito larvae are abundant, and then have considerable 

 time available for perfecting the system and ditching more distant marshes. Experi- 

 ence showed that a considerable number of salt-marsh mosquitoes bred on that portion 

 of Jamaica Bay northwest of the village were brought in by southwest followed by 

 northeast winds. This led to the extension of ditching operations some 2 miles beyond 

 the village limits. The work in the immediate vicinity of Lawrence was done partly 

 at public expense assisted by contributions from owners benefited, though it was 

 impossible to secure the cooperation of persons owning the distant marshes, which 

 latter were drained entirely at village expense. The existence of such breeding areas 

 is an imposition upon adjacent communities, and it is only a question of time before 

 public opinion will demand a law either compelling owners to abate such nuisances 

 or else provide for their suppression at public expense. The money invested by 

 Lawrence in this work, a total of less than $10,000, has amply justified itself in vastly 

 improved conditions. The village and its vicinity have been entirely freed from 

 breeding places, although it is subject to late summer invasions by hordes of mosquitoes 

 when favorable winds bring them from undrained marshes. Even this will be obviated 

 when the value of the work becomes more generally appreciated, and then the cost of 

 the operations will be amply returned in increased land values, to say nothing of the 

 satisfaction accruing from the absence of these dangerous and annoying pests. 



On the north shore of Long Island, in Connecticut, and especially 

 in the vicinity of New Haven, certain simple ditching operations have 

 been carried on which have resulted, at a comparative inexpense, in 

 a very considerable reduction of the mosquito supply. 



THE CALIFORNIA WORK. 



In California, in connection with work carried on by the California 

 State Agricultural Experiment Station, in 1905, some excellent work 

 was done under the auspices of the Burlingame Improvement Club, 

 in San Francisco, under the direction of H. J. Quayle, of the California 

 Experiment Station. The territory involved is included in the upper 

 portion of the San Francisco Peninsula, extending from South San 



