284 TREUBIA VOL. II, 2--4. 
SWELLENGREBEL (°°) furthermore records for Semarang an enormous 
increase of rossii mosquitos towards the end of 1918. With this he 
connects the fact that for various places on the North coast of Java beside 
the maximum malarial mortality in July, August and September another 
similar though smaller maximum is known at the beginning of the rainy 
season. If this view is correct, Myzomyia rossii GILES, even though its 
importance as a malaria-transmitter is very much less than that of Myzomyia 
ludlowi THEOBALD, would after all not be so innocuous as is sometimes 
assumed. 
I wish to revert for a few moments to the enormous significance, 
frequently referred to in the above, of the ponds of Heemraad and 
Heemraad-Oost as /zdlowi breeding places. In those ponds, as | remarked 
in the foregoing, the /zdlowi production in the months of April up to and 
including September 1919 was greater than the production of rossii; as 
far as the remaining Batavia empangs are concerned this only occurred in 
1919 in the ponds near Pekulitan, in June and July; in the ponds near 
Antjol, in May; and likewise in May in the ponds near Jaagpad, in these 
latter however it was only from the larvae and pupae collected that more 
female /zdlowi than rossii-mosquitos emerged, whilst on the contrary 
more female rossii than /udlowi mosquitos were captured in mosquito-nets 
(cf. Tables VI, VII and X)'). 
Moreover at salinities between 25 and 29.9 °/., an excess of the /zdlowi- 
production over that of rossii occurred only in the ponds near Heemraad 
(cf. Tables VII and IX). 
I do not venture to decide the question as to whether this great importance 
of the empangs of Heemraad and Heemraad Oost as breeding-places of 
ludlowi is connected solely with the fact that in these ponds the salinity 
even in the course of a very dry East monsoon always remains comparatively 
low, owing to which the fauna of the aquatic stages of /udlowi in these 
ponds can maintain itself throughout the year. It is not impossible that 
there may be yet other factors which for the present escape our notice. 
The greatest /zdlowi-production we met with amounted to 647 ludlowi 
females per 10 M? of the pond surface in one night. This was recorded 
on July 25th 1919, in the ponds of Heemraad, at a salinity of 9.3 Joo (cf. 
Table V). The number of mosquito nets set on that occasion was 8, yielding 
together a harvest of 518 female /udlowi (cf. Table IV). 
As regards the greatest production that we could record in each of 
the other parts of the Batavia empang region, this will be found, together 
with that of Heemraad, in the subjoined list, derived from Tables V 
and IV. 
1) As appears from Table VI in May 1919 larvae and pupae were only once 
collected in the ponds near Jaagpad. Mosquito-nets however were set there 9 times in 
that same month. 
