388 BIOLOGICAL CONTROL 



and the control attained appears to be of a permanent nature. 

 The whole history and the biology of the host and parasite are 

 described in an elaborately produced book by Tothill, Taylor and 

 Paine (1930). 



The success achieved by the introduction of Ptychomyia led to 

 the further application of biological methods of control in the 

 Islands. The scale insect Aspidiotus destructor is another severe 

 enemy of coconut besides attacking bananas, avocardo and other 

 plants. It is not known how, or exactly when, this insect 

 became introduced into Fiji, but several attempts have been made 

 to control it by parasite introductions without success. It was 

 not until 1928 that certain predators of the family Coccinellidae 

 were introduced from Trinidad, where they had been observed to 

 exercise notable control over the same host scale in that island. 

 The Coccinellid Cryptognatha nodiceps soon proved itself superior 

 to the other species that were introduced along with it. Only nine 

 months after liberations were made in Fiji the scale insect was 

 brought under control in all the more important islands of the 

 group. In his full account of this campaign Taylor (1935) states 

 that the scale has become reduced to negligible proportions and 

 an apparently permanent check has been maintained upon it. 



The complete success of the introduction of C. nodiceps is 

 attributable to a combination of factors. First, it breeds 

 continuously with a high rate of multiplication throughout the 

 year in Fiji. It is a voracious predator, both as larva and adult, 

 and in the latter phase it is long-lived. Secondly, it has remarkable 

 powers of dispersal. Thirdly, it has no serious enemies in Fiji. 

 Finally, the Cryptognatha is able to survive even when the 

 Aspidiotus has become reduced to a condition of great scarcity. 

 In this connection, the fact that it has an alternative host in 

 another scale insect, namely, Diaspis pentagona, which is not a 

 serious pest in Fiji, is important. 



An even more recent success is that achieved in the repression 

 of the leaf-mining Hispid beetle of the coconut, Promecotheca 

 reichei, an account of which has been published in detail in a 

 special volume by Taylor (1937). The introduction of the Chalcid 

 Pleurotropis parvulus from Java in 1933 led to the rapid and 



