PROC. EXT. SOC. WASH., VOL. 22, NO. 5, MAY, 1 920 IO7 



by insects, submerging in mill ponds during the flight periods, 

 and rapid utilization of the felled timber before the insects have 

 had time to injure it. 



It was accidentally discovered by the writer that direct ex- 

 posure to the sun can be utilized in connection with forest man- 

 agement and lumbering practices as a highly efficient method of 

 prevention or control of certain of the more destructive tree- 

 killing and wood-boring insects. 



In the summer of H)17 several hickory logs containing Cyllene 

 -pictus (Drury) in the pupal and immature adult stages were ac- 

 cidentally left in direct sunlight for several hours. Later in the 

 same day these insects were removed from their cells and isolated 

 in vials. As they were taken out it was found that many from 

 the top side of the logs were dead. This discovery, together 

 with the well known fact that logs exposed to direct sunlight are 

 in many localities attacked only on the under surface, immediately 

 suggested possibilities of utilizing the heat of the sun in control 

 or prevention of damage by certain insects. The same summer 

 a few tests were made by turning both infested and uninfested 

 logs in the sun which gave promise of future possibilities where 

 other methods were not practical. 



Since then further experiments have been made at Falls Church, 

 Va. ; Yicksburg, Miss., and Tucson, Ariz., giving conclusive evi- 

 dence as to the effectiveness of this method under certain con- 

 ditions. The experiments were primarily based on the turning 

 of infested logs in the sun and a series of observations on about 

 three million feet of ash logs cut at different seasons and handled 

 in various ways. 



In the following paragraph several examples of these prelim- 

 inary experiments are given to illustrate the effectiveness of this 

 method. 



At Sabino Canyon, Ariz., during June, 191S, an assortment of 

 infested mesquite sticks containing several species of Bostrichids, 

 both larvae, pupae and adults, several species of Chrysobothris 

 larvae and larvae of Cyllene antennatns were removed from par- 

 tial shade where they had been infested and placed in the direct 

 sunlight. Two days' exposure killed 4() c ( of all larvae, pupae 

 and adults to the depth of one-half inch, one week's exposure 

 7.")' ( to depth to three-quarters of an inch, and two weeks' expo- 

 sure over '.>()' ', to the same depth. 



From June to September uninfested green mesquiu- sticks were 

 laid out in the sun and turned w r eekly for 4 to 10 weeks, then placed 

 in the shade. A few ( 'hrysobothris and Bostrichids attacked the 

 under side of the logs at first but all were killed during turning 

 and no subsequent attack resulted. 



