LATER WORK IN CALIFORNIA Zll 



Icerya scale, mealybugs (P seudococcus spp.) next demanded 

 attention. The introduction of the Coccinellid Cryptolcemus 

 montrouzieri by Koebele from Australia about 1892 is familiar 

 to entomologists, and the most interesting feature respecting 

 this predator is the fact that in areas where it has been unable 

 to maintain itself, it can be induced to dominate its prey by 

 continuous laboratory breeding and distribution. It seems certain 

 that the citrophilous mealybug {P, gahani Green), a citrus pest 

 of first importance, has been largely kept under control by this 

 method. There are a number of special insectaries (Fig. 93), 

 located in infested counties or districts, which are given over to 

 the rearing and distribution of the Cryptolcemus, an enterprise 

 which has been developed on a commercial basis {vide Smith and 

 Armitage, 1931). In these structures the mealybugs are reared on 

 shoots of potato previously sprouted in the dark, and when a 

 sufficient supply of the host is available the Cryptolcemus is 

 introduced and allowed to multiply freely under favourable 

 conditions of constant temperature. During 1924, 4,038,238 

 Cryptolcemus were reared and distributed at an inclusive cost of 

 $48,750, and the total citrus area infected with mealybugs was 

 approximately 20,000 acres. In comparison with this method it 

 has been pointed out that the cost of a single spraying for that 

 acreage would amount to about 8200,000, and several spray 

 applications per year are necessary, in order to ensure control of 

 the pest. Notwithstanding the destruction exercised by the 

 Cryptolcemus, the citrophilous mealybug has steadily increased its 

 range in Southern California ; in 1928 the infested area increased 

 to about 50,000 acres, and some 40,000,000 of the predators were 

 being bred for distribution. Believing that the efficacy of biological 

 control would be strengthened if additional enemies, especially 

 internal Hymenopterous parasites, _^ were available, efforts have 

 been made to locate the country of origin of the pest. In 1916 and 

 1917 Clausen explored Japan, China, Formosa and the Philippines 

 without success. Further search was made by F. Silvestri, who 

 was already in the Orient, in the countries visited by Clausen, 

 and also in Indo-China and the Malay Archipelago without 

 revealing its presence. In 1927 Compere located the insect in 



