1906.] Natural Enemies of Insect Pests. 



689 



The Mediterranean Fruit Fly {Ceratitis capitata) has for many 



years been a serious pest in various places, notably in Australia, 



South Africa, and Bermuda. Recently 



Natural Enemies j t has been suggested that the original 

 of Insect Pests. t . ■ . , . - s 



home 01 this destructive pest is Brazil, 



where it is kept in check by the existence of natural enemies, 

 especially a species of Ichneumon fly and a species of Staphy- 

 linid beetle. The fact that the fruit fly is known as a pest in 

 Bermuda, where natural enemies do not occur, while in Jamaica 

 it is not a serious pest, has suggested that enemies allied to the 

 Brazilian species exist there, and the Government of Bermuda 

 is making efforts to introduce and establish the natural enemies 

 of the fruit fly found in Jamaica. A proposal was also made to 

 introduce the small green fly-catching lizard of Jamaica as well 

 as certain birds with a view to combat the ravages of the fly. In 

 connection with this latter suggestion, Dr. Sharp, of Cambridge, 

 communicated in 1904 to the Board some observations which 

 are of general interest, apart from the special case to which they 

 more particularly refer. 



The chief enemies of insect? are other insects and minute 

 fungi. Insects in the natural conditions of their existence are 

 kept in check by a host of parasitic insects, of which various 

 kinds are specialised for attacking their food-insect in particular 

 stages. It appears probable that under natural conditions 

 80 or 90 per cent, of the annual increase of insects is destroyed 

 by other insects. 



On the other hand, vertebrates take but a small proportion, 

 and are not specialised to attack any particular species of insect, 

 The greatest destruction they effect is probably exercised on the 

 larvae. The fly that is destructive to fruit in Bermuda is not 

 specially suited for attack by vertebrates — the larva is concealed, 

 and the flies themselves affect situations on trees and flowers 

 where they would only occasionally be caught by lizards or 

 birds. It may therefore be taken as certain that the introduc- 

 tion of these animals into Bermuda would not diminish the 

 number of flies to any extent. At present it appears that the 

 number of flies is only limited by the supply of their food. As 

 they have enormous powers of multiplication, the destruction of 



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