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DIVISION OF ENTOMOLOGY. 



Honolulu, April 15, 1920. 

 Board of Commissioners of Agriculture and Forestry, Honolulu. 



Gentlemen: — I su1)mit herewith, in compliance with the law, 

 a brief report of the activities of the Division of Entomology in 

 the annual period January 1st to December 31st, 1919. 



The propagation and distribution of beneficial insects, particu- 

 larly the fruit fly, horn fly and corn leaf hopper parasites, has been 

 continued throughout the year and a tabulation below gives the 

 number liberated. 



No new field work has been undertaken, on account of the unset- 

 tled conditions abroad and poor transportation facilities, but 

 through the cooperation of the California State Horticultural 

 Commission a pupal parasite of one of the destructive cabbage 

 insects (Picris rapae — cabbage worm, imported cabbage butter- 

 fly) was received by mail from California, and has been propa- 

 gated in our insectary. from which large colonies have been 

 liberated in cabbage fields on Oahu and Hawaii. The establish- 

 ment of the insect has not yet been determined. 



Considerable time has been given to the study of the termites 

 or white ants, which are becoming severely and alarmingly de- 

 structive \vith the increase and spread of two lately immigrant 

 species. 



An investigation w^as begun during the summer on the natural 

 control of the dung-flies in Hawaii with the purpose in mind of 

 securing additional agents, if conditions warranted it, and so im- 

 proving the control. These investigations remain incomplete, 

 more urgent matters necessitating their suspension temporarily. 



In September an infestation of the forest ferns by the Aus- 

 tralian weevil Syagrius fulritarsis was discovered at 29 Miles 

 from Hilo on the Hilo-Kau road. On account of the wealth of 

 fern growth in this region and the importance of the ferns as 

 part of the ground cover in the Hamakua forest reserve, it was 

 decided to attempt to control the outbreak and prevent the spread 

 of the weevil beyond the confines of the small area in which it 

 was determined to be present. This necessitated the destruc- 

 tion of all ferns in the area as far as possible, \vhich were cut 

 and burned ; thereafter, the ground cover was either fired or 

 poisoned as far as possible to destroy crawling weevils, which 

 might have escaped the initial treatment, and every vestige of 

 fern plant on which the beetle could subsist ; and an artificial bar- 

 rier of crude oil was laid to contain the insect. At the same time 

 an investigation was made of the weevil's history, habits, cyclical 

 development, etc, which had not previously been done, although 

 the weevil has been known in the islands fifteen years. This 

 work has occupied the division almost exclusively during the re- 



