314 Report of the Departmext op Entomology op the 



ing stage was reached and oiie insect succeeded in reaching full 

 development. 



General summary. — These experiments are of practical interest 

 in indicating the temperature required in a cellar for cold storage 

 of trees or fruit to prevent the development of young larvae or 

 to kill the adult females, which if able to survive the cold would 

 probably produce young, as was the case with the adults referred 

 to on page 313 very soon after being brought into warmer tem- 

 peratures. This is of especial interest in connection with cold 

 storage of fruit. It will be noticed that at a temperature of 45° 

 F. development was merely checked and continued when the 

 scales were brought into higher temperature, while at 35 F. none 

 of the young scales survived. 



MEANS OF LOCAL DISTRIBUTION. 



It is during the active stage that the insect is distributed 

 locally. There are three principal agencies which aid in local 

 distribution. First, the activity of the larva which enables it 

 to migrate from one place to another; second, the wind which 

 may carry infested leaves and twigs about; and third, insects, 

 birds and similar agencies. The ability of the larva to migrate 

 over smooth surfaces has been previously referred to. 



Wind. — To ascertain the probability of the larvse being carried 

 on foliage by the wind, 200 pear leaves were picked and carefully 

 examined October 1, and although the larvae were numerous on 

 the trees none could be found on the leaves. Ten leaves were 

 then placed on the ground and a larva on each. In one hour all 

 had gone except two which remained three hours. October 4, 

 when the larvae were numerous and active on the infested pear 

 trees, 1680 green leaves on the trees were carefully examined 

 and but 54 larvae were found. A larva was then placed on a 

 pear leaf which was released from a point abont 10 feet from 

 the ground. It was carried by a light breeze about 16 feet and 

 when examined the larva had disappeared, evidently having been 

 blown off by the wind. This was repeated six times, the leaves 



