135 



more especially Hottonia greatly contribute to the aeration of the water. In this con- 

 nection attention must of course mainly be paid to the tracheal gills; with regard 

 to this point I refer the reader to pag. 15. 



At the same time as the hibernation of the mosquitoes in the larva stage 

 was pointed out it was also shown that mosquitoes could hibernate in the imago 

 stage. In addition to the above-named statements by Howard, Dyar and Knab and 

 by Eysell I more especially refer to the following authors: Westwood (1872 

 p. XVI and 1876 p. VII); Wade (1888 p. 52); Gray (1900 p. 250); Annett and 

 Dutton (1901 p. 1013); Cazeneuve (1910 p. 155); Eckstein (1919m p. 530); most 

 probably most of the indications belong to C. pipiens and T. annulata; the modern 

 explorations in Germany commenced with a view to mosquito destruction (Eckstein, 

 Bresslau; Teichmann, Prell), all seem to show that all mosquitoes which hiber- 

 nate in our houses in Europe really belong exclusively to C. pipiens and T. annulata. 



With regard to the Aedini, as far as I know, we have never in Europe found 

 any of them hibernating in houses; that they should hibernate as imagines in Na- 

 ture itself has often been supposed, but never thoroughly corroborated. On the other 

 side communications from the arctic regions, from the Siberian Tundras (Finsch 

 1876) as well as from the arctics of North America (Sterling 1891, Steward 

 1891; with regard to this littr. see Nuttali. and Shipley 1902 p. 63) seem to 

 show that the Aedini of the arctic region are able to hibernate in the frozen 

 masses of the tundras and in clefts and hollows of the snow, appearing in milli- 

 ons as soon as the first sunbeams in spring heat the surface of the snow. Further 

 explorations may show how these communications are to be brought into accord- 

 ance with those of Knab with regard to the hibernation of the Aedini as eggs, if 

 not under arctic conditions, still under very hard climatic ones, with high degrees 

 of frost. Even in our country the possibility is not quite excluded that some of 

 our Aedini should be able to hibernate as imagines. I more especially refer to the 

 late broods of O. caspius and communis. 



With regard to the egglaying and related processes of our Central 

 European Aedini we have only very few observations. With regard to all those species 

 which lay their eggs in batches (C. pipiens and T. annulata) and about which we know- 

 that the single batches are laid at smaller and greater intervals, we are able to speak 

 of a series of brqods in the single generation. With regard to the Aedini this is 

 not possible; most probably the eggs are thrown off uninterruptedly during the whole 

 summer. As far as I know, more thorough explorations have only been carried on 

 with one single species, the yellow fever mosquito: Aedes calopus- (Stegomgia fasciata), 

 only found a few times in southern parts of Europe and last in England (Lang 1920 

 p. 112). Macfie (1915 p. 205) indicates that the maximum life of the female is sixty 

 two days; Fielding (1919 p. 25) has kept the species living for 93 days. The first 

 blood-meal is taken on the second or third day, and three or four days elapsed 

 between each act of oviposition. Egglaying continued throughout life. Even with 

 regard to Stegomgia fasciata Bacot (1916 p. 1) has mentioned the fact, highly 



