226 



There is a g-reat mortality amoug the young before they take their 

 first meal. A female that lives 4 mouths would deposit from 

 10 to 12 pupae ; for one living 6 months the number would be 15 

 or more. A sheep free from ticks may be kept for months beside 

 a heavily infested one, with a partition only three feet high 

 between them, without becoming infested. Slieep ticks have 

 very little instinct for migration, this being especially true of 

 the females. 



BuTTEicK {P. L.). The Effect of Tides and Rainfall on the Breeding' 

 of Salt Marsh Mosquitos. — Jouin. Econ. Eiifuin., Coiiconl, 

 vi, no. 4, Aug. 1913, pp. 352-359. 



The author was placed in charge of a camiuiign against mos- 

 quitos in New Haven, Connecticut. The chief species to be 

 controlled was the banded salt-marsh mosquito, Cule.v sollicitans, 

 Walk. The eggs are laid on the salt marsh mud and lie dormant 

 until covered by water, either tide or rain. They then hatch in a 

 few hours, and in G-15 days the adults emerge. The marshes where 

 the mosquitos breed are usually flooded at certain periods when 

 the tides rise above the general level. Shortly after this happens, 

 a brood of mosquitos is liable to emerge. In an oiling cam- 

 paign, a knowledge of the time of the unusually high (or perigee) 

 tides is of the greatest importance, as it gives an opportunity for 

 making preparations for controlling the brood following upon it. 

 The paper deals largely with the methods, meteorological and 

 otherwise, used in making a forecast as to when these tides will 

 occur. The height of the maximum high tide at a given station 

 for eacli day of the mosquito season is plotted as a curve. The 

 next point is to determine at what height of tide a given marsh is 

 flooded. This may be done (1) by setting a tide gauge at some 

 convenient point on a stream or in the marsh; (2) by ascertaining 

 the general level of the marsh with reference to mean low water ; 

 and (3) by visiting the marsli at high tide on difl'erent days, and 

 determining by observation at w^hat height of tide they are 

 flooded. By drawing a line across the high tide curve, at a 

 height corresponding with the height of the flood line, it can be 

 seen at a glance at what time flooding Avill talce place. The 

 following shows how the method works in practice. On Saturday, 

 10th August 1913, the maximum high tide was predicted from 

 the curve as 6'8 feet. Tliis is sufficient to flood the West River 

 Marshes. Development in ordinary August weather generally 

 takes about one week; hence oiling, to be successful, had to be 

 done before the following Saturday night, ITth August. 



Although rainfall is a faclor in the abundance of mosquitos, 

 it does not necessarily follow that the more rain the more mos- 

 quitos. So far as salt-marshes are concerned the time and amount 

 of the precipitation are of great importance. A rain-storm 

 occurring when the tides almost roach the flood lino may bo suffi- 

 cient to raise the water-level so that a brood is produced; wliile 

 at another period, when the tide is low, the same amount of rain 

 may be carried off without its first covering the marsh. Rain 



