BUREAU OF ENTOMOLOGY. 321 



material has been found to be very effective for use in the (hist form 

 against lice of cattle ami other domestic animals, as well as af^ainst 

 fleas. The findint^ of an ett'ective ilry treatmenjt for lice is a matter 

 of much importance to the dairymen and stockmen of the Xorth, 

 where the use of sprays or dips is hazardous during the winter, when 

 the lice usually become most troublesome. Thousands of doUai-s are 

 spent each year for lice powders, and many of these are entirely 

 ineffective. 



Insects affecting the health of man. — The investigation of ma- 

 laria mosquitoes at Mound, La., has been continued during the year 

 and combines a general biological study of the local species with 

 observations on the effect of certain control measures instituted by 

 the International Health Board. 



The field covered by the biological investigation includes: (i) Lar- 

 val studies — principal breeding areas, conditions favoring maxinnmi 

 production, normal emergence from unit areas, distance from source 

 to food supply: (2) adult studies — normal abundance around dwell-' 

 ing houses, monthlv and seasonal variations in abundance, distance 

 of flight, and dispersion of adults; (3) natural control — studies of 

 insect, plant, and fish enemies; and (4) dissection of adult Anopheles 

 to determine percentage of infected mosquitoes in nature and their 

 distribution. 



The study of experimental control measures carried out in coopera- 

 tion with the International Health Board includes: (1) An experi- 

 ment to determine the effect of collections of adult mosquitoes inside 

 houses; (2) effect of screening the ordinary tenant house upon ma- 

 laria incidence and Anopheles abundance; (3) effect of clearing 'ind 

 impounding a 3-mile section of a natural bayou; and (4) effect of 

 moving tenant houses to" more favorable locations, an investigation 

 which includes a general stmly of the influence of location on malaria 

 incidence and Anopheles prevalence. 



During the year a series of enlarged photomicrographs of different 

 stages of malaria infection in the mosquito host was exhibited at the 

 Hot Springs (Ark.) meeting of the Southern Medical Society. A 

 preliminary paper on normal abundance of Anopheles around tenant 

 houses was read before the New Jersey Mosquito Association and 

 published in the proceedings of their society. 



INSECTS AFFECTING FOREST RESOURCES AND SHADE TREES. 



This work has been continued under the direction of Dr. A. D. 

 Hopkins. 



Insects affecting forest trees. — The work at the field stations in 

 California and Oregon, and in the northern and southern Rocky 

 ^Slountain States has been almost entirely in response to requests by 

 the Forest Service, Xational Park Service, and private owners for 

 examination and report on infested timber and cooperation in con- 

 ducting control projects. 



The southern Oregon-northern California control project. — 

 One of the most extensive control operations against a tree-killing in- 

 sect ever undertaken is that of the southern Oregon-northern Cali- 

 fornia cooperative control project. Continued and increasing depre- 

 dations by the western pine beetle on the yellow-pine timber on more 

 than 1,300,000 acres of National Forest, Indian reservation, and pri- 



