86 THE INSECT WORLD. 
They then leave their abode and go into the ground, there to 
change into pupe. 
The Ortalide 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 
ahalflong. It is of rather a metallic black colour, its head ight 
yellow, the edges of its eyes white, and the tarsi red. The wings 
have four broad black stripes. 
The Olive Dacus (Dacus olee, 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 yel- 
low spots, and its hind part, 
as well as its antenne and 
wings, are of the same colour. The wings are transparent, reflect- 
ing green, gold, pink, and blue, according as the rays of light fall 
upon them, and are remarkable for having a small black spot at 
their extremity. 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 
frances to French agriculture. 

Fig. 65.—Dacus ole. 
M. Guérin-Méneville has made some valuable observations on 
the Olive Dacus, and, at the request of the Imperial Society of 
Agriculture of Paris, has indicated the way to preserve the olive 
from these ruinous larvee, which generally destroy two crops out 
of three. We will borrow the following details from this learned 
entomologist. ‘At the time when the olives are formed, the 
Dacus proceeds to place an egg under the skin of each of the fruits. 
