128 



varying length; most probably blood-nutriment is necessary or desirable between 

 every deposition ; we therefore find larvae in the cisterns in all stages of development. 

 With regard to the enormous amount of eggs which may be deposited, in some 

 localities, I refer the reader to a valuable paper by Glaser (1917 p. 531). 



It is very difficult to make clear how many generations are produced in the 

 course of a summer. The common opinion is that the number of generations is 

 very large; I for my part regard this supposition as quite wrong. I do not think 

 that it exceeds three or rarely four; Speiser (1908 p. 395) has arrived at a similar 

 result, he indicates two or three generations, but every one of these generations has 

 most probably from two to four broods. The cisterns teem with larvae and pupa? 

 till about the middle of September; then all the larva? are almost of the same size 

 i. e. no more eggs are deposited. On ls /x the cisterns still contain pupa?, but from 

 the first days of November all the broods disappear. These indications are in ac- 

 cordance with those from Strassbourg (Eckstein 1919j p. 95). He maintains that 

 five generations may be the rule in a year. Here however the females appear in 

 Nature already by '-'O/in Tp. 11° C. Eggs were found on 7/rv; in the first part of 

 May the first generation appears. In our country the lirst generation does not ap- 

 pear before the middle of June. At Strassbourg the development from egg to 

 imago takes three weeks in April, in summer only two. With regard to the influ- 

 ence of temperature on the life cycle of C. pipiens see also Kramer (1915 p. 874). 

 That the power of propagation may be regarded as extremely high is pointed out 

 by many authors: Glaser (1917 p. 531); Davis (1906 p. 368). When in German 

 literature from recent years we read about the enormous amounts of C. pipiens 

 females wintering iu houses, we may also conclude that our climatic conditions are 

 by no means able to produce such enormous C. pipiens swarms; though I have 

 examined numerous cellars I have never seen them in such incredible numbers as 

 indicated in literature. 



It has often been pointed out that C. pipiens breeds in water of extremely 

 nasty condition, and my own experience is in accordance with this; often they are 

 found in localities where we should not expect to find mosquito larva? f. i. 66 feet 

 below ground (Mac Gregor 1916 p. 142). See also Manoloff (1910 p. 52). I sup- 

 pose that a more thorough exploration will clear up the questions relating to broods 

 and generations. When it has not been done here, it is partly as indicated on p. 127 

 because it could not be cleared up simultaneously with the other explorations, partly 

 also from another cause. It is rather difficult in our country to find farms where 

 the explorations can be carried out in the course of some years; mosquito larva? 

 in the drinking water of the cattle and in the cooling-water of the dairies are with 

 some reason regarded as inexcusable and must be combated when found. More 

 than once I have found the water barrels cleaned, when some weeks later I came 

 back, all further observations on this spot being then almost useless. 



Also in our country the water barrels and cisterns in the cow-stables are by 

 no means the only known breeding places for C. pipiens. In the so-called settlement 



