ESSAYS 465 



normal salinity. The larvae will also hatch out quite successfully after being 

 transferred into fresh water at an early age. 



It was not possible to organise any extensive searches for hibernating 

 females during the winter 1920-21, but a certain number of Culex and Theo- 

 baldia were discovered and destroyed by fumigation. 



Early in 192 1 the Island was divided up into eighteen administrative 

 sections, each one being in charge of a " section secretary," and a circular 

 explaining the objects of the campaign was drawn up and sent to every house- 

 holder. The circular drew attention to the habits and life-history of mosquitoes, 

 to the methods of destro3a.ng their larvae, and to the success achieved by 

 anti-mosquito organisations abroad ; concluding \nth a summary of the 

 various ways in which assistance was required. Each circular was accom- 

 panied by a stamped envelope bearing the address of the appropriate section 

 secretary and by a " reply card " worded as follows : 



" / approve of the objects of the Hay ling Mosquito Control, and I hope to 

 assist in one or more of the ways mentioned below : 



" (i) By carrying out as far as possible such instructions as may be supplied 

 to me from time to time for preventing mosquitoes breeding in my house, garden, 

 etc. 



" (2) By reporting to the secretary of my section the location of any pond, pool, 

 ditch, water-tank, etc., in which I observe any larvcB (' wrigglers '). 



" (3) By organising or taking part in field expeditions for seeking out ' breed- 

 ing places ' and dealing with them when found. 



" (4) By collecting mosquitoes and mosquito larvcs in accordance with direc- 

 tions to be supplied to me. 



" (5) By giving a donation of £ s. d. 



" You may therefore enter my name on the List of Members." 



Instructions were printed on the above cards requesting the recipients 

 to indicate by crosses the ways in which they expected to help. In spite of 

 the novel character of the scheme, the response elicited by the circular was 

 extremely encouraging. 



A systematic " charting " of all the ponds, ditches, marshes, and other 

 " water places " ^ on the Island was at once commenced, the particulars of 

 each case being given a " register number," and entered on a separate page 

 of the " Control Record " book of the Section (Fig. i), the lower part of the 

 page being reserved for the entry of details referring to future observations, 

 larvicidal treatments, etc. Any larvae found during the preliminary 

 inspection were, of course, destroyed. 



As each water-place was thus registered, its representation on a large- 

 scale wall-map was coloured blue and connected by a red indicating line with 

 the outer of two concentric circles (f and fV inches diam.) drawn on the map, 

 the particular register number being inscribed within the smaller circle. The 

 space between the circles was coloured red, to direct attention to the possible 

 danger of larvae being present whenever there was no definite information 

 to the contrary. 



Since the completion of the registration, the progress of the work through- 

 out the Island has been continuously indicated on the Control Map by 



1 Writers on this subject are frequently at a loss for some general term 

 to describe " anything in which water has collected or is liable to collect." 

 Such expressions as " water receptacle " or " water container " nearly meet 

 the case, but do not sound correct if applied with reference to a ditch or marsh. 

 " Water-lodge " has been proposed, and seems worthy of consideration. 

 In this article the term " water- place " has been tentatively used, chiefly 

 in the hope of eliciting some better suggestion. 



