6 BULLETIN 1235, U. S. DEPARTMENT OP AGRICULTURE. 



THE INSECTARY. 



Practically all of the life-history studies of the codling moth were 

 made in the insectary, which was located in the rear of the laboratory 

 (PI. II, fig. 1) . This was arframe structure 30 feet long by 12 feet wide, 

 with a slanting roof dropping 40 inches to a minimum height of 8 

 feet. The sides were covered with wire screen, permitting a good 

 circulation of air and preventing the escape of moths and the entrance 

 of intruders. It was shaded and protected from the wind by several 

 buildings, a large tree, and canvas awnings. 



A thermograph and maximum and minimum thermometers in the 

 insectary were used to compute the temperature records referred to 

 in this bulletin in connection with the charts and diagrams. A ther- 

 mograph operated in the orchard where the spraying experiments 

 were conducted showed the temperatures there to have a lower 

 maximum and a higher minimum, but showed that the monthly 

 mean temperatures for the growing season were only 0.79° F. higher 

 than those at the insectary. The climatological data given in Table 1 

 are taken from the records of the United States Weather Bureau 

 station, which is about 3 miles from the insectary, and show the 

 monthly mean temperatures of the same period to be higher by 

 4.1° F. The daily mean temperatures reported by the Weather 

 Bureau are determined by averaging the maximum and minimum 

 temperatures for the day. Those obtained in the insectary and 

 orchard were computed by weighting the hourly readings recorded 

 by the thermographs for the seasons of 1919 and 1920, while for 

 1921 the daily average temperatures were computed from the ther- 

 mograph records for each two hours. 



SEASONAL-HISTORY STUDIES OF 1919. 



The seasonal-history studies of the codling moth were commenced 

 in the spring of 1919 with observations on the pupation period of 

 wintering larvae. The season of 1919 began with approximately 

 normal temperatures, but an abnormal drop occurred on May 29 

 and 30, the minimum temperature on the latter date being 32° F. 

 The mean temperature for June was below normal, after which the 

 weather was about normal for the rest of the fruit season. The 

 rainfall was deficient, the year's total being 5.5 inches, or 1.79 inches 

 below normal. Apple trees bloomed at Yakima April 25 to 30, and 

 the calyx spray was applied about May 10. 



The tables showing the seasonal history of the various stages 

 should be considered separately, as, owing to accidents, natural 

 mortality, or the removal of individuals for other reasons, it is not 

 possible to carry all the individuals through all stages. The life- 

 cycle tables, however, summarize the life history of those individuals 

 which were reared from the egg to the adult stage 



WINTERING LARVAE. 



Wintering larvae construct heavy, closely woven cocoons, usually 

 well hidden under pieces of loosened bark on the tree trunk, in the 

 crotches of the tree, and in the soil at its base. When the weather 

 begins to warm up in the spring the larva opens one end of the 

 cocoon and forms a silken exit tube to the nearest place free from 

 obstruction, through which the pupa wriggles when ready to disclose 

 the moth. 



