THE VALUE OF THE IBIS 



411 



know that the Kestrel especially and also many other 

 of the slower flying hawks feed largely on insect life. 

 The grasshoppers have other enemies in Australia, for- 

 tunately, as when they lay their elongated eggs in the 



ground in small bunches, cockatoos often find them out, 

 and digging up the ground with their strong beaks, 

 devour many thousands of them, yet, I am afraid these 

 birds often do not get the credit they deserve. 



THE BATTLE AGAINST FOREST INSECTS 



IMPORTANT results have been obtained in investi- 

 gations of insects affecting forest resources, accord- 

 ing to the recent annual report of the chief of the 

 Bureau of Entomology, U. S. Department of Agriculture. 

 An extract from the report follows : 



"An especial investigation of the insect damage to 

 crude spruce products for airplane stock in the States of 

 Washington and Oregon showed that the greater part 

 if not all of the damage could be prevented by proper 

 methods of logging and production with little or no 

 additional cost. 



"Exhaustive studies of insect investigation and con- 

 trol were continued in the Sequoia and Yosemite Na- 

 tional Parks. Much new information has been gained, 

 and the methods of gathering and compiling field data 

 have been standardized. 



"A special study was completed on the interrelation 

 of forest fires and insects on an area of about 8,000 acres 

 in southern Oregon. This area had been under obser- 

 vation since 1914, and the fire had burned over about 

 800 acres in 191 8. The records show that previous to 

 the fire the insects had killed 485,000 board feet of 

 timber. The fire killed 170,000 feet, and subsequently 

 the slightly fire-injured as well as the uninjured trees in 

 the burned area were killed by beetles, which were at- 

 tracted from the surrounding areas. It was noticed that 

 the infestation in the burned area increased more than 

 1. 000 per cent, but it was found that the infestation in 

 the surrounding areas decreased. It was also found that 

 the broods of the beetles in the fire-scorched trees failed 

 to develop tu much beyond the original number that 

 attacked the trees. So the fire did not contribute to an 

 increase of the beetles in the general area or to the 

 starting or extension of an epidemic of beetles. This 

 result is of extreme interest and hardly to be expected. 



"The most careful study ever made of the history of 

 an epidemic infestation by tree-killing beetles was com- 

 pleted and a report submitted during the year. In the 

 Rogue River area in about 48,000 acres, near Ashland, 

 Oregon, the western pine beetle in 1914 caused the death 

 of 346,000 board feet of pine-timber. In 1915, 1,615,000 

 board feet were killed; 1,383,000 feet in 1916, and 608,- 

 000 in 1917. A count of the young and matured stages of 

 the beetles that developed in an average foot of bark, 

 and also of the number of exit holes through which the 

 beetles emerged to attack other trees, showed that there 

 was a notable decrease in numbers during the develop- 

 ment of the broods each year in the infested trees on 

 account of the increase of natural enemies and other 

 disturbing factors. This helps explain why these beetle 

 epidemics rise and fall within a limited period of years, 

 and it explains how the western forests of yellow pine 

 are naturally protected from total destruction. These facts 



are especially significant in connection with the applica- 

 tion of the percentage principle of control, as by aiding the 

 natural forces which work against the abnormal increase 

 and spread of the beetles complete control may be gained. 

 The history of this epidemic shows the importance of 

 prompt recognition and prompt treatment of a threatened 

 outbreak in order to prevent the great loss of timber 

 which would occur before natural control became 

 operative. 



"Another special study was made of the number of 

 all stages of the western pine beetle in 330 square feet 

 of infested bark selected from 67 trees, which repre- 

 sented an average infestation within an area of approxi- 

 mately 36 square miles. It was shown that there is a 

 large percentage of mortality between the young and 

 matured stages in the developing broods, but that 

 normally an average of about 150 beetles to the square 

 foot of bark developed to that adult, or reproductive, 

 stage; which would be 50,000 beetles to the average in- 

 fested tree, or, say 39,000 beetles to 1,000 board feet of 

 timber. Since it requires an average of about 10 beetles 

 to the square foot to attack and kill a vigorous, healthy 

 tree, it will be seen that all the pine timber of the western 

 forests would soon be destroyed were it not for natural 

 and artificial control. 



"Experiments to determine the time of year to cut and 

 the methods of handling mesquite for fuel, posts, etc., to 

 avoid destruction by wood-boring insects, have been 

 nearly completed, and the results show that serious loss 

 in the Southwest can be prevented by cutting the trees 

 in the late fall and early winter and piling the wood in 

 loose piles until it is thoroughly dry. Damage to posts 

 can be prevented by cutting them at any time and laying 

 them on the ground where they will receive the full force 

 of the sun, turning them occasionally so that the young 

 stages of the borers will be killed by the heat. 



"Studies of damage to lead telephone cables in Cali- 

 fornia by a wood-boring beetle have been continued, and 

 the results so far show that the beetle is able to penetrate 

 alloyed substances that are considerably harder than lead. 

 The problem is still unsolved, and it will be difficult to 

 find a practical means of controlling this pest, which is 

 able to put hundreds of telephones out of commission by 

 boring holes in the cables, through which the water 

 enters, rendering the wire connections useless until the 

 place is found and repaired. 



"Continued experiments with chemical substances ap- 

 plied to finished and crude forest products show that 

 very few of the many substances that have been tried 

 are effective, and, with crude products, none of them is 

 so economical as simple and inexpensive management 

 in logging and manufacture which will render the con- 

 ditions of the bark and the wood unfavorable to attack.- 



