29 



Mttsca domestica hibernates as a mobile adult, and probably in a 

 prc-imaginal stage as well. The same applies to Fannia canicularis 

 and Siomoxys calcitrans. 



Lyperosia irritans probably hibernates in a pre-imaginal stage. 

 Nothing is known about the adult stage in this connection. 



Though the information obtained is scanty, it appears that each 

 species is able to hibernate in different stages. Mobile and motionless 

 imaginal hibernation does not, however, appear to occur in one and 

 the same species. 



Eckstein (F.). Aus einer Feldstation fiir Stechmiicken. [^"tes from 

 a Mosquito Field-station.] — Zeitschr. angeiv. Enloni., Berlin, vi, 

 no. 2, February 1920, pp. 338-371, 11 figs. [Received 2nd 

 December 1920. J 



These observations were made near Mannheim, at a bend of tlie 

 Rhine, which at times floods portions of it. 



The following mosquitos are found : — Culicincs : Culex pipicns, 

 C. hortensis [territans), Theohaldia {Cidicella) morsitans, T. {Culiseta 

 anivulata, Taeniorhynchus -{Mansonia) richiardii, Ochlerotaius macidatus 

 {Cidicada cantans), 0. (C) vexans, 0. genictdatus (C. lateralis), 0. 

 (C) ammlipes, 0. (C.) diversiis, 0. (C.) ornatus, and Aedes cinereus. 

 Anophelines : Anopheles macnlipcnnis, A. hifurcatiis, and A. {Coelo- 

 diazesis) pliimbeiis. 



0. macidatus is the commonest species, and with 0. vexans is 

 responsible for the plague of mosquitos at Mannheim. This is important, 

 for spraying the breeding-places in spring will result in a notable 

 decrease of the mosquitos in summer, because there is only one 

 generation, derived from the eggs that have hibernated. It is of course 

 necessary to spray repeatedly during the summer against the species 

 that have several generations. 



The principal object of the author's visit was to test the various 

 repellents that have been recommended against mosquitos. It was 

 found that a given repellent does not always act in the same way against 

 different species. Under otherwise similar conditions the author was 

 bitten more often when wearing dark colours than when wearing 

 light ones. In no case did any of the 28 substances tried, or mixtures 

 of them, prove of more than fugitive value. A powerful odour does 

 not appear either to repel or attract mosquitos. For practical use 

 the repellent should be harmless, colourless, odourless, capable of 

 keeping mosquitos about 3 feet away, light in weight, cheap, and active 

 for 6-7 hours. Experiments in fumigation showed that the mosquitos 

 tend to become stupefied, but not killed. The palhatives advised 

 by Ewing are good [R.A.E., B, vii, 25], but ordinary 70 per cent, 

 alcohol proved quite satisfactory. 



In a 1 per cent, solution of sodium silicate mosquito larvae die after 

 20 hours, and pupae in 5. Nitre cake, consisting of anhydrous sodium 

 sulphate and acid sodium sulphate [R.A.E., B, vi, 137], is useless 

 against Ctdex pipiens in Germany, for the larvae and pupae are not 

 killed, nor is the hatching of the eggs prevented. 



Anopheles macidipennis and A. bifurcatus are abundant. Some of 

 the former (both larvae and adults) are infested with small red mites, 

 without any apparent effect. In the aquarium the mites remained on 

 the cast skins, thereby losing their hosts. 



If larvae of different species are kept in an aquarium it will be seen 

 that Cidex pipiens and A. macidipennis usually remain at the surface ; 



