A. D. Peacock 
245 
The conclusions, therefore, are that waters with a vegetation consisting 
of grass or algae or with vegetation in which grass or any alga is predominant 
are almost entirely Anopheline and that all waters should be regarded as 
suspected Anopheline habitats. 
The Degree of Infestation of Anopheline Waters. In regard to the number 
of larvae found in the waters it has been found necessary to establish a 
standard by which to estimate the degree of infestation of such waters. 
While the number of dips taken at a water varied with the conditions 
discovered, the result of usually 20 dips per water, taken at various parts, 
was judged to indicate the degree of infestation, and, in practice, it was found 
that the catches yielded extremes, there being captured either few or many. 
The term “few” refers to total catches up to 10 or thereabouts and the term 
“numerous,” interpreted rather broadly, to those in which the average yield 
per dip was 3 and over. 
The number of records is 106, from which it is found that the number of 
waters with few larvae was 67 (63-2 %), those with numerous larvae 22 (20-7 %), 
while 17 (16*1 %) records are doubtful. 
It was impracticable to ascertain the Anopheline population of any water 
but it may be recalled that in two instances, at Moulle and Arques, it would 
run into many thousands. 
The Degree of Anopheline Infestation of the Second Army Area. In esti¬ 
mating the significance of these results regard must he taken of the comparatively 
few pools examined in certain regions , the inexperience of some of the collectors 
and the lateness of the season. These factors would tend to produce results which 
would indicate that the number of Anopheline ivaters and the degree of infestation 
of the districts were lower than those actually obtaining. 
The weather conditions during the survey, on the whole, were good for 
the season of the year, there being a number of hot days. For about seven 
days the weather was wet, bleak and cold but it is unlikely that it influenced 
the results to any great extent. 
In estimating, from the data discovered, the Anopheline conditions existing 
in the Second Army area three questions must be answered, viz.: 
(1) What is the geographical distribution of Anopheline waters? 
(2) What proportion of waters is infested with Anophelines? 
(3) What is the degree of infestation of these waters? 
In regard to (1) it can be stated that Anophelines are generally distributed 
throughout the Second Army area. Out of 20 neighbourhoods examined, 
only in 4, Herzeele, Ouderzeele, Steenvoorde (south and west) and Gode- 
waersvelde, Berthen and Boeschepe (high land), were no Anophelines found, 
but it is quite probable that more careful search would yield positive results. 
It may also be added that the greater number of Anopheline waters were in 
close proximity to billets. 
In answering the questions (2) and (3) it would be incorrect to total the 
