TEMPERATURES FATAI. TO LARV^ 251 



Bureau of Entomology. These vvoocl-boring grubs develop from eggs 

 laid by beetles in crevices of the bark. The banded ash borer flies in 

 the early spring, in the extreme South, from the first part of March 

 to the first part of April, while in the Northern States it flies from 

 the middle of April through May. In the South the first flight of the 

 red-headed ash borer coincides with that of the banded ash borer ; 

 however, the red-headed borer continues to appear all summer until 

 the middle of October, while in the North it appears only during 

 June. In those States between the northern and southern limits of 

 distribution the dates of flight are intermediate. These beetles will lay 

 eggs only on logs which are not seasoned, i.e., the inner bark must be 

 still sappy; also the bark must be present. After the eggs hatch the 

 larvae bore beneath the bark from 4 to 6 weeks before entering the wood. 



To avoid the injury by these borers it is therefore essential that the 

 logs be removed promptly from the woods during the flight period of 

 these beetles or not later than 4 to 6 weeks after the earliest dates of 

 flight. They should be promptly sawed or the bark removed before 

 storage, or else they should be placed in water. Four months' sub- 

 mergence in water makes the wood unattractive to the borers and will 

 prevent future attack. 



Material. — The material used in these experiments consisted of 

 approximately 20 pieces of ash, 3 feet long, cut from young trees from 

 3 to 8 inches in diameter. It was cut in April, 1,920, and held at the 

 Bureau's Eastern Field Station, East Falls Church, Virginia, where 

 it was attacked in June by the borers. It was shipped in September 

 to the Forest Products Laboratory. 



Methods of Sawing. — Inasmuch as this borer confines its activities 

 to the sapwood, it was essential that the sapwood be unmolested as 

 far as possible. Therefore, th'e 3-foot sections of the trees were merely 

 quartered or halved instead of being sawed into boards of a given 

 thickness. 



Condition of Larvcc. — The majority of the larvae were full grown 

 in their pupal cells in the wood, while a smaller percentage were still 

 feeding in the wood. The treatments were observed on both stages 

 of larvae, but no noticeable dififerences in results were observed. 



Methods of Procedure. — This study was conducted with a view of 

 determining not only the effect of temperature but also that of relative 

 humidity on the borer. In order that these factors might be isolated, 

 three types of experiments were made. 



