Insect Notes fok 1920 11 



green. It seemed very peculiar that the galls should break just at this 

 point w4ien others were still on the tree and needed considerable pull to 

 make them break. An unusually large number of these leaves falling 

 one day made a study of the problem imperative. To make a long 

 story short, a red squirrel Sciiinis hitdsoiiius Erx.. was the depredator. 

 The squirrel would reach for the galls and eating into them, as he 

 would a nut, evidently enjoyed the taste of the enclosed plant lice. The 

 leaf portion became free and dropped. From thirty to forty seconds 

 would suffice for one gall. He went from leaf to leaf with great rapid- 

 ity. The feasting was kept up for an hour or sometimes longer, until 

 the himger was satisfied. One squirrel could therefore do considerable 

 damage. Since that time the operation has been seen many times. 



In one wood where there were not supposed to be any red squirrels 

 this phenomena of leaf dropping occurred. As our observations did 

 not extend over a long time it could not be proved that squirrels were 

 the depredators. The large gray squirrel, S. caroliiiciisus Gon., has 

 never been seen to do the injury. 



In connection with the forest insect work it has been shown by 

 experiment that insects working in logs are much more subject to the 

 action of external physical factors than was formerly supposed. Logs 

 in deep shade are apparently less subject to injury by the more serious 

 wood destroyers than those in more open situations. This is partly 

 due to a retarding of the rate of development in the cool, shady loca- 

 tion and partly to the fact that fewer eggs are deposited in logs under 

 very shady conditions. This suggests the possibility of shading logs 

 to protect them from the attack of the more injurious species of insects. 



On the upper side of logs exposed to the direct rays of the sun, 

 subcortical temperatures of 60 degrees, C, or more have been observed. 

 In fact, in some logs the temperatures on almost any bright day during 

 the summer will pass above the fatal point for insects. This is not, 

 however, true of all logs. The temperature beneath the bark is gov- 

 erned by light intensity, angle of incidence of the sun's rays, color, sur- 

 face, structure, thickness of the bark, air temperature, air movements, 

 evaporation from bark surface, and proximity to the other radiating 

 or absorbing surfaces. White pine logs often reach very high tempera- 

 tures, while norway pine logs are comparatively cool. 



One of the problems studied during the past year has been the 

 spreading and adherence of arsenical sprays. Considerable progress 

 has been made on both phases of the problem and the details will soon 

 appear in print. Much, however, remains to be studied. From the re- 

 sults of this investigation certain new fields of insecticidal experimen- 



