The time required for passing throu'^h each stage "was quite 

 varied in the ■various experir.ents d\:iring IQIQ* For easier compar- 

 ison I present in Table VI the results oi' t^iree tests 



TABLE VI 



Duration of the different larval stages and the average te:aperat- 

 ure during three tests in 1919 



Stage I II III StEges I thru III 



Days Teiap» Days Tevap Days Ter.p. Days Temp, 



*Did not reach the 4th stage 



The figijre showing the average tesiperature is only partly correct 

 since it often happens that at one nonent larvae in various stages 

 are sinultaneously present© The averages are therefore taken on 

 days during which the preponderance of Irrvac pressni; vrere in the 

 applicable stagec Also the figures show the highest daily terqper- 

 ature taken b etvre en 2 and 3 p.ru 



The Table shov;s clearly the relation betvrecn the te];perature 

 and the nuriber of days required to pass tlirough one stcgce There 

 raust hoTicver be other influences v/hich doternino these diu^ations* 

 The nature and quantity of food as vrell as cleanliness are undoubt- 

 edly factors of equal inportancec This appeared convincingly fron 

 the last test taken in 1920 during the cold and wet August dayso 

 The average daily tcnperature v*t.s then 16o8°, still sone specinens 

 arrived in the 4th stage within 12 days v/hile in all 27 per cent 

 of the larvae reached that point o At that tijjo it was however 

 possible to keep the vjr.ter in the roaring tanlcs as well as the 

 tanks thens elves very clean* In 1919 it T<r.s just this circuri- 

 stance v/hich offered the greatest difficulties* 



The results of test in 1920 are best shovai in the forn of a 

 Trblc (VII). 



I have arranged the tests in three groups, the first v/ere 

 r.Tadc in June, the second in July and the last in the beginning of 

 August. The percentages are considerably higher than in 1919 and 

 increase steadily in the three succeeding groups. 



TABLE VII 

 Results of the 1920 experinents 



Tank Qiiantity of Duration Per Cent of Tenp© 



number larvae of stages larvae 



at start I II III planted 



III 345 4-5 4-5 4 11*6 20°8 



-etcs- 



136 



