615 THE INSECT WORLD. 



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

 change into pupae. 



The Ortalidte 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 a rather 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 olece, Fig. 65) is a little fly, aboul 



half the size of the house fly 



^ of ashy grey colour on the back 



its head orange-yellow, it; 

 eyes green, and its foreheac 

 yellow, marked with two larg< 

 black spots. The thorax is 

 adorned with four lightish yel- 

 low spots, and its hind part 



Fig.65.-Dacu 80 le*. ^ ^ ^ ^ antenne anc 



wings, are of the same colour. The wings are transparent, reflect 

 ing green, gold, pink, and blue, according as the rays of light fal 

 upon them, and are remarkable for having a small black spot a 

 their extremity. The abdomen is of a fawn colour or orange 

 yellow, spotted with black on each side. This fly performs suddei 

 and jerking movements ; it keeps its wings extended, and rathe: 

 jumps than flies. It is a destructive insect, a perfect scourge, whicl 

 causes every two or three years a loss of five or six millions o 

 francs to French agriculture. 



M. Guerin-Meneville has made some valuable observations o] 

 the olive dacus, and at the request of the Imperial Society o 

 Agriculture of Paris, has indicated the way to preserve the oliv 

 from these ruinous J.arva>, which generally destroy two crops ou 

 of three. We will borrow the following details from this learnec 

 entomologist. " At the time when the olives are formed, th 

 dacus proceeds to place an egg under the skin of each of the fruits 



