86 THE INSECT WORLD, 



opening the truffle, the larvae of the insect of which we are speaking 

 will be found inside. These larvae are white and very transparent. 

 Their mouth is armed with two black hooks, by means of which they 

 dig into the truffle in the same way as other larvae dig into meat. 

 The excretions of these little parasites cause the truffle to become 

 decomposed and rotten. In a few days the larvae become full-grown. 

 They then leave their abode and go into the ground, there to change; 

 into pupae. j 



The Ortalidd! form a tribe which is remarkable for the upright 

 carriage of the wings, which are generally speckled, by the vibratory 

 movement of these organs, and especially for the cradle chosen by 

 them for their progeny in fruits and grains. Nature seems to have 

 assigned to each species its own particular vegetable. 



We will only mention here the Cherry-tree Ortalis, whose larva 

 lives on the pulp of that fruit. This fly is about a line and a half 

 long. It is of rather a metallic black colour, its head light yellow, 

 the edges of its eyes white, and the tarsi red. The wings have four 

 broad black stripes. 



The Olive Dacus {Dacus oiece, Fig. 65) is a little fly, about half 



the size of the house fly, of ashy 

 grey colour on the back, its 

 head orange-yellow, its eyes 

 green, and its forehead yellow, 

 marked with two large black 

 spots. The thorax is adorned 

 with four lightish yellow spots, 

 and its hind part, as well as its 

 antennae and wings, are of the 

 same colour. The wings are 

 transparent, reflecting green, 

 Fig. 65.-Dacus oies. gold, pink, and blue, according 



as the rays of light fall upon 

 them, and are remarkable for having a small black spot at their ex- 

 tremity. The abdomen is of a fawn colour or orange-yellow, spotted 

 with black on each side. This fly performs sudden and jerking 

 movements ; it keeps its wings extended, and rather jumps than flies. 

 It is a destructive insect, a perfect scourge, which causes every two 

 or three years a loss of five or six millions of francs to French 

 agriculture. 



M. Guerin-Meneville has made some valuable observations on 

 the Olive Dacus, and at the request of the Imperial Society ot" 

 Agriculture of Paris, has indicated the way to preserve the olive from 



