Feb. 2, 1920 



European Frit Fly in North America 



463 



Table III. — Variation in the time of emergence of adults of Oscinis frit in each brood, 

 with reference to the number of days from emergence of their parents 



Number of daj's since emergence 

 of parents. 



24. 



25- 

 26. 

 27. 

 28. 

 29. 



z°- 

 31- 

 32- 



Z2,- 

 34- 

 35- 

 36. 

 40. 

 42. 

 44- 



45- 

 46. 



47- 



49- 

 52- 



58- 



Total by broods . 

 Average 



Brood number. 



35 

 49-7 



II. 



10 



3 

 4 



S 



I 



4 

 3 



41 



28.5 



IV. 



2 



45- 5 



Total 

 by days. 



4 



3 

 2 



6 



16 



99 



The period from adult to adult may be considered as consisting of: 

 (a) The preoviposition period; (b) the egg instar; (c) larval instars; 

 and (d) the pupal instar. Since the sum of these (adult to adult) varied 

 from 21 to 58 days, naturally the components would vary accordingly — 

 not, however, in strict proportion, because all periods become suc- 

 cessively accelerated while approaching the heat climax of summer and 

 are retarded after passing it. Making the best approximation possible, 

 the records obtained seem to bear out the following division of the entire 

 period : 



PERCENTAGE OF TIME IN LIFE CYCLE 



Preoviposition 14 



Egg II 



Larva 50 



Pupa ; 25 



Total 100 



It would be more logical to count this period from &gg to Q.gg, but 

 oviposition is very difficult to observe and the data upon that subject 

 are very meager. The emergence of the adult is the easiest point to note, 

 and is the one on which the record is most complete. 



