THE CODLING MOTH IN THE YAKIMA VALLEY. 



61 



and several inches of soil was placed in them, about the pieces of 

 wood, which latter were too smooth to afford a cocooning place for 

 the worms above the soil surface (PL II, fig. 2) . Each cage was stocked 

 with 160 worms in September, 1919, but the extreme cold in Decem- 

 ber froze those in the band cages and some in the soil cages. Con- 

 sequently, in February, 1920, 100 additional worms were placed in 

 each band cage and 30 in each soil cage. These cages were set in 

 the open, side by side, the soil cages being sunk in the ground so 

 that the soil surface in the cages was level with that outside. Records 

 of the emergence of the moths were made daily, and 60 moths were 

 secured from the two band cages and 134 from the two soil cages. 



In 1921 the experiment was repeated, 100 worms having been 

 placed in each cage in the fall of 1920. Emergence records were 

 kept as before, 98 moths being secured from each pair of cages. 

 In 1922 records were again obtained, 130 moths being secured from 

 the band cages, and 57 from the soil cages. 



In Table 47 the records of the emergence of moths from the bands 

 and from the soil are compared for the three years, the dates being 



fiven on which specified percentages of the total moths had emerged. 

 n 1920, moths emerging from the soil appeared from 6 to 13 days 

 later than those from the bands, while in 1921 this interval was 

 only from 1 to 4 days. In 1922 the moths emerged from the soil 

 cages earlier than from the others, for the most part. The reduc- 

 tion of the interval in 1921 was due partly, if not wholly, to a period 

 of unseasonably warm weather occurring from May 13 to June 9, 

 and covering practically the entire emergence period of these moths. 

 In 1922, the weather also was unseasonably warm throughout 

 June. Thermograph records were kept both of soil and of air tem- 

 peratures, and the daily mean soil temperature every year averaged 

 from 2 to 4° higher than the air temperature. 



It is evident from these experiments that, although the soil tem- 

 perature averages somewhat warmer than that of the air, the emer- 

 gence of moths from the soil may be somewhat delayed and may be 

 more prolonged than that of moths from the trunks of trees. This 

 might be even more pronounced in orchards where cover crops shade 

 the soil. 



Table 47. — Emergence of moths of the spring brood of the codling moth from bands 

 and from the soil, Yakima, Wash., 1920, 1921, 1922. 



Per cent 

 emerged. 



1920 



1921 



1922 



Date emerged. 



Inter- 

 val. 



Date emerged. 



Inter- 

 val. 



Date emerged. 



Inter- 

 val. 



From 

 bands. 



From 

 soil. 



From 

 bands. 



From 

 soil. 



From 

 bands. 



From 

 soil. 



1 



10 

 25 

 50 

 75 

 100 



May 10 

 May 15 

 May 18 

 May 25 

 May 30 

 June 13 



May 16 

 May 26 

 May 31 

 June 3 

 June 8 

 June 29 



Days. 

 6 

 11 

 13 

 9 

 9 

 16 



May 11 

 May 15 

 May 20 

 May 24 

 May 29 

 June 6 



May 12 

 May 19 

 May 23 

 May 26 

 May 30 

 June 6 



Days. 

 1 

 4 

 3 

 2 

 1 

 



May 17 

 May 22 

 May 27 

 May 30 

 June 2 

 June 18 



May 16 

 May 18 

 May 26 

 May 31 

 June 3 

 June 15 



Days. 

 -1 



-4 



-1 



1 



1 



-3 



