28 



These observations prov^e the inadequacy of the present-day method 

 of winter measures against mosquitos, which only aim at destroying 

 the adult females, 



Eckstein (F.). Witter ung und Stechmuckenplage. [Weather and 

 Mosquitos.] — Zeitschr. angewandte Entom., Berlin, vi, no. 1, 

 1919, pp. 93-105, 1 fig., 1 chart. 



A number of observations, made at Strassburg in the spring of 1918, 

 are recorded regarding the influence of weather on the increase of 

 mosquitos. 



Culex pipiens depends on climate in the sense that an early spring 

 and a warm, dry summer are particularly favourable to its increase. 

 Furthermore its oviposition appears to depend somewhat on the 

 occurrence of thunder-showers, for egg-rafts are very abundant 

 afterwards. It is calculated that where conditions allow of 5 genera- 

 tions the descendants of one female may amount to 3,200,000 in a 

 year. If unfavourable weather reduces the generations to 4, the total 

 \vill fall to 160,000, while it may rise to 64,000,000 if 6 generations 

 occur. As Anopheles maculipennis also hibernates in the adult 

 stage its appearance is likewise dependent on the beginning of the 

 warm weather. Its development however only permits of 2-3 annual 

 generations. The hibernating larva of A. bifurcatus scarcely increases 

 in size during the winter, and growth in spring depends on the tem- 

 perature of the water, which is obviously related to weather conditions. 

 Ochlerotatus {Culicada) vexans, 0. (C) nigrinus and Aeies cinereus 

 oviposit at the edges of temporary pools and the eggs only hatch 

 when wetted in spring by a rise of the water-level due to local rain or 

 to a rise of the subsoil water ; in winter, wetting the eggs does not 

 usually cause them to hatch. The eggs laid by the resulting imagines 

 equally require to be wetted, and this explains why these species are 

 rare in short, dry summers. In spring the Rhine is swollen by the 

 snow meting in the Alps and a rise of about 6 ft. will flood many areas 

 near Strassburg and produce swarms of mosquitos. Culicada cantans 

 and 0. (C.) nemorosus hibernate in the egg-stage and have only one 

 generation in the summer. The 6ggs are deposited in the second 

 half of summer. 0. {Cidicada) ornalus breeds in water in hollow 

 trees. The eggs of each generation are laid above the edges of the 

 water and heavy rains are required to raise the level of such collections 

 of water and cause them to hatch. Development is greatly accelerated 

 by a rise in temperature, requiring 36 days at 48° F. (9° C.) and only 

 10 days at 75° F. (24° C). Hot, dry weather alternating with heavy 

 rains therefore provides the optimum conditions for a large increase of 

 0. ornatns. The chart accompanying this paper gives the above 

 information in graphic form. 



Glaser (F.). Die Schnalcenbekampfung nach den neueren Erfah- 



rungen. [Anti-Mosquito Work on Modern Lines.] — Vereinigung 



zur Bekdmpfung der Schnakenplage, Mannheim, 4 page leaflet 



dated December 1919. 



The recent researches prosecuted by Bresslau, Eckstein and the 



author have supplied the necessary basis for anti-mosquito work in 



Germany, where hitherto the methods employed were chiefly suited to 



