328 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



centage of injury b}' Leaf -rollers in favor of the spray. ^ It will be fiir- 

 ther noticed that, in the check, the Leaf-roller injury^ reached it's cli- 

 max late in the season. 



The chart illustrating the Number of Generations was seciired from 

 larvae reared in confinement and checked with orchard conditions. 

 The first two generations were reared through completely but the last 

 generation was calculated from eggs laid towards the end of July. At 

 this time and during the first of August newly hatched larvae were 

 found abundant in the orchards. 



STUDIES OF SANNINOIDEA OPALESCENS EDW. IN OREGON 



By Frank H. Lathrop, and A. B. Black, Oregon Agricultural College Experiment 



Station, CorvaUis 



In 1916 the Oregon vStation undertook an investigation of the Wes- 

 tern Peach and Prime Root Borer, Sanninoidea opalescens Edw. with 

 Mr. G. F. Moznette in direct charge of the work. Upon the resigna- 

 tion of Mr. Moznette in 1917, the project was taken over by the senior 

 author, who was later joined by the junior author in the prosecution 

 of the work. 



The formulation of an effective and economical means of control 

 has been the primary object of the investigation. Life history studies 

 have been conducted as a minor part of the work. 



Life History Studies 



Winter Co"nditions. Overwintering larvae seem to be active during 

 warm periods and it is probable that some growth takes place during 

 this season. Our observations show that during periods of cold rainy 

 weather the larvae tend to leave their tunnels and work in the gum 

 and frass as well as the soil immediately surrounding the tree. Many 

 of these larvae lie dormant in silken cells which they spin against the 

 tree trunk beneath the soil surface. 



The winter cell is constructed with one side against the bark of the 

 tree. In shape it is oval. The outer wall consists of a very thin silken 

 membrane, concavo convex in form, forming a cell in which the lar 



^Six applications were made both to the sprayed and Dusted plats. A 90-10 

 Dust was used with the addititon of 1 % Nicotine, as Nicotine sulphate. On the 

 sprayed plats Lime Sulphur and Arsenate of Lead was used with the addition of 

 Black Leaf 40 in the first four sprays. 



