BUREAU OP ENTOMOLOGY. 229 



Experiments relating to the spread of the gipsy-moth larvae by the 

 wind have been continued, and many special tests have been made 

 to determine the amount of spread in certain selected areas, as this 

 information is very useful in planning the held work. 



Experiments with dilferent materials for banding trees are under 

 way and the new tree-banding material that is being used is the re- 

 sult of some of the experimental work already conducted. 



The development and improvement of high-power spraying ma- 

 chines has been given considerable attention, and the three new motor- 

 truck spraj^ers recently acquired are a vast improvement oyer any 

 of the spraying outfits used heretofore. 



Careful studies are being made of the means by which the female 

 gipsy moth attracts the males, in order that this information may be 

 used to advantage in the field work. The sense organs of the cater- 

 pillars are being studied in connection with the tree-bancling and 

 other insecticide work in order that more knowledge may be obtained 

 as to the exact effect of repellents in control work. 



A study of the increase or decrease of the gipsy moth in the field 

 in selected localities has been continued, and special information as 

 to the principal factors that bring about decrease in the field under 

 normal conditions is being obtained. An investigation of the effects 

 of temperature and humidity, both on the insects themselves and on 

 the increase of their parasites and natural enemies, including dis- 

 eases, is being continued. 



Parasite and disease work. — Careful studies are being made of 

 the increase of the introduced parasites under field conditions in dif- 

 ferent localities. All the species previously reported as having be- 

 come established have been found to occur in greater numbers than 

 ever before. Several species that previously were known to have 

 established themselves but had not increased to any great extent have 

 been found in considerable numbers. Among these should be men- 

 tioned Blepharipa scutellata^ one of the tachina-fly parasites of the 

 gipsy moth, and two others, Parexorista chelonlae and Zygohothria 

 nidicola, which attack the caterpillars of the brown-tail moth. 



The effect of parasites has been more noticeable than usual. Col- 

 onization has been limited to a few species that have not become dis- 

 tributed over the entire infested area. During the fall of 1916 more 

 than 2,500,000 individuals of Schedius kuvanae were liberated, and in 

 the spring of 1917 about 8.500,000 individuals of Anastatus hifasci- 

 atus were colonized in the New England States. Of Apanteles mela- 

 nosceUs, 5,500 individuals have been colonized in the field. 



Work on the wilt disease of the gipsy moth has been continued 

 both in the laboratory and in the field, and progress has been 

 made in clearing up some of the obscure points concerning this 

 organism. It has been shown conclusively that this disease may be 

 distributed by insects whose habits bring them in contact with 

 affected caterpillars. 



A new caterpillar disease of the gipsy moth is being studied sys- 

 tematically and has proved to be very destructive to caterpillars 

 under laboratory conditions. An attempt is being made to study its 

 behavior under field conditions, and numerous experiments are being 

 carried on to determine its value in this country. The disease is 

 prevalent in Japan. 



