437 



Galls frequently found on the leaves of poplars are caused by the 

 Aphids, Pemphigus popuUcaulis, Fitch, and P. popiilitransversus, Riley. 

 Defoliation of these plants was complained of in several instances, 

 and it is thought to be ])ossibly due to squirrels {Sciunis hndsoniiis) 

 feeding on the galls and their contents. Experiments with insects 

 working in logs suggest the possibility of shading logs as a protection 

 against their depredations. 



Chapman (R. N.). Observations on Mites infesting Flour and Mill 



Feed.— 7M Rept. Minnesota State Ent., Agric. Expt. Sta., Univ. 

 Farm, St. Paul, 18th June 1921, pp. 20-25. 



A brief summary is given of the general life-history and possible 

 means of combating Tyroglvphids infesting flour and mill feeds [R.A.E., 

 A, vii, 91]. 



GRAHA:\r (S. A.). Factors influencing the Subcortical Temperatures 



of Logs.—lSth Rept. Minnesota State Ent., Agric. E.xpt. Sta., 

 Univ. Farm, St. Paul, 18th June 1921, pp. 26-42, 5 plates. 



In this paper, which is part of a more extensive work dealing with 

 the oecology of wood-boring insects, the factors influencing the sub- 

 cortical temperature of logs are considered. These include solar 

 radiation, character of bark, air temperature and movement, evapora- 

 tion from bark surfaces and proximity to other radiating or absorbing 

 surfaces. 



Observations indicate that the weekly turning of logs as recommended 

 by Craighead [R.A.E., A, viii, 365] may prove an effective means of 

 destroying many wood-boring insects ; but it cannot be applied in 

 all cases, as some logs, particularly those with thick, light-coloured 

 bark, will remain below the temperature fatal to insects even on very 

 bright warm days. In using this method the position of the log with 

 reference to the sun must be considered ; those lying east and west 

 will often reach a higher temperature in a small area than those lying 

 north and south, but the latter will be heated over a much greater 

 surface 



Cook (W. C). Studies on the Flight of Nocturnal Lepidoptera.— 



18th Rept. Minnesota State Ent., Agric. Expt. Sta., Univ. Farm, 

 St. Paul, 18th June 1921, pp. 43-56, 2 plates. 



The seasonal and meteorological relations of adult Noctuids belong- 

 ing to the genera Agrotis, Agroperina {Septis), Sidemia, Euxoa, Feltia, 

 Cirphis, Polia, etc. are discussed. As a result of observations made in 

 1920 it was found that temperature and humidity are more closely 

 correlated to the numbers caught than pressure. Humidity is the 

 most important factor studied. Any increase up to about 54 per cent, 

 in the humidity at 7 p.m., which represents a higher degree during 

 the night, tends to increase the catch, but beyond that value it 

 is decreased in almost the same proportion. Although temperature 

 has always a positive influence, it is larger below than above optimum 

 humidity The correlation coefticients, although not an accurate 

 measure of relationship between factors, are at least a relative or 

 qualitative measure. 



