Preface. 



x he history of the work which I hereby take the liberty to offer to the 

 scientific world has been rather peculiar. More than twenty years ago I saw that 

 our temporary forest ponds which got water in November — December very often, a 

 few days later, contained living mosquito larvae; I saw that these larva; hibernated 

 under the ice and that they could be found again when the ice melted in the 

 spring. To me it was rather an astonishing fact to find in 1900 air-breathing 

 insect larva? below the ice, locked out by the ice from the atmospherical air. In the 

 following years I often visited the temporary ponds in spring and ascertained that 

 they teemed with mosquito larvae. Even the slightest study with a magnifying glass 

 showed that these larvae differed very much from the hibernating larvae. 



In the admirable chapter in "Histoire des insects" Reaumur has shown that 

 Culex pipiens hibernates as imago and lays its eggs in batches, eggboats. In his 

 work "History of Aquatic Insects" Miall has had nothing to add; as far as I know, 

 Reaumur's exposition of the biology of C. pipiens has for more than a century been 

 used as a model of the development of all mosquitoes. In accordance with this 

 fact year after year I searched for the eggboats in the temporary ponds of our 

 forests; I never saw a single one. 



In the following years I slowly came to understand that there was also upon 

 another point a striking discrepancy between what we have learned and what I 

 found out on studying Nature herself. Scientists as well as ordinary people have all 

 been inclined to suppose that a great number of generations are hatched during 

 the year. Without any more thorough exploration I felt sure that most of the mos- 

 quitoes really had only one single generation. In the spring of 1905 I tried to hatch 

 the above-named two mosquitoes, the one with the hibernating larvae, and the 

 one with the larva 5 which only appeared after the ice had melted; the former larva 

 had very large antenna? and a long sipho; the latter very small antenna 1 and a very 

 short sipho; of course I got two species of mosquitoes; but the one with the 

 hibernating larva was unquestionably new to our fauna. Having however taken 

 material from different forest ponds, to my astonishment I saw that those mosqui- 

 toes which derived from the hibernating larva' always gave the same species, 

 whereas those deriving from the larva? in spring, gave specimens which unquestion- 

 ably belonged to two or three different species. 



