BUREAU OF ENTOMOLOGY. 261 



insect control clone in the State. This method of control has practi- 

 cally eliminated this mealybug from upward of 500 acres near Up- 

 land, Calif., and, in fact, over most of the district infested by this 

 insect, and for the first time in years the owners of these orchards 

 are able to sell their fruit in prime condition at the highest market 

 price. This method of control will be rapidly extended os'er the en- 

 tire infested district. 



In connection with the investigation of the two principal mealy- 

 ])Ug enemies of citrus plants in southern California, the parasitic and 

 predatory enemies of these insects have been further investigated as 

 also the symbiotic relations of those insects with the Argentine ant. 



Tlie department lias cooperated with the California authorities in 

 the determination of the best methods of exterminating the European 

 snail (Helix pisana) which has become established in a small canyon 

 or district near San Diego. As a result of this investigation and of 

 various conferences the method of control now^ being carried out by 

 the State is the burning over of the district with torches fed with 

 oil under pressure totally to destroy the vegetation. This snail was 

 possibly introduced by some foreigner familiar with its food value 

 in Europe, without thought as to its tremendous possibility for harm 

 to cultivated crops. 



Citrus fruit insects in Florida. The work under this project 

 during the year has been largely limited to demonstrational work in 

 the aid of increased production. Spraying demonstrations have been 

 conducted widely throughout the State. A revised schedule for 

 fumigation and treatment of trees to prevent insect injury has been 

 worked out for the grapefruit, and a Farmers' Bulletin (No. 1011) 

 has been issued entitled " The Woolly White Fly in Florida Citrus 

 (iroves." Some special lines of investigation have had to do Avith 

 the stabilizing of insecticides especially wJiere the only water avail- 

 able is obtained from deep wells containing a large percentage of 

 mineral elements which more or less affect the stability of certain 

 emulsions and other insecticides. The work in Florida has had par- 

 ticular relation to the citrus white fly, the rust mite, and the com- 

 mon Florida scale insects. The work in the control of citrus pests 

 in Florida has shown the greater availability of liquid sprays over 

 the fumigation methods commonly followed on the Pacific coast. 

 During the last two years, however, considerable demonstration work 

 has been done vvith fumigation in Florida by a private concern, the 

 results of which have been carefully examined by the expert of this 

 department as a protection to citrus growers and to determine that 

 any claims made are fully justified. 



Investigations of insects affecting ]mango, guava, avocado, and 

 OTHER subtropical FRuiTs.-^Thc maugo and avocado and other fruits 

 mentioned under this heading are being commercially developed on 

 a considerable scale in southern Florida. A station jfias been estab- 

 lished at Miami in cooperation with the Office of Foreign Seed and 

 Plant Introduction of the Bureau of Plant Industry of this depart- 

 ment to investigate the peculiar insect enemies of these fruits. Due to 

 the proximity and commercial connections of southern Florida with 

 Bermuda, the West Indian Islands, and Central America, this region 

 is especially open to invasion by important fruit pests, and several of 

 these have already gained entrance. One feature of the project, 



