166 ANIMAL PARASITES AND MESSMATES. 



the caterpillars. These insects contribute more effectually 

 to the destruction of caterpillars than all the means 

 employed by man. To arrest the Pyralis of the vine, its 

 cultivators encourage the little Chalcis (Chalcis minuta) ; 

 and it has lately been recommended to introduce the 

 acarus which attacks the Phylloxera, in order to lessen 

 the number of this new pest. Do not aphides also 

 prevent the too rapid development of certain plants ? and 

 the black species which lives on Windsor beans has 

 doubtless suggested to the gardener that he ought to cut 

 off the head of the plant when the flowers appear. 



Some other hymenoptera may be mentioned: for 

 example, the Evaniadse, the Chalcididse, as well as the 

 Tachinarise, which are remarkable for this kind of life. 

 At the moment when the mining hymenoptera introduce 

 into their hiding-places the insects which they have 

 seized, and which they destine for their young ones, 

 the Tachinarise introduce themselves by stealth, and lay 

 their eggs on these provisions. Each kind of tachinarias 

 attaches itself to a particular insect. There is one essen- 

 tial difference between them and ichneumons, that the 

 females of the latter perforate the skin of their victims 

 with a pointed instrument, and cause their eggs to pene- 

 trate to the interior of the entrails; while the mother 

 tachinse, less cruel, are contented to lay their eggs on the 

 surface of the skin, and leave to the larva the care of 

 penetrating into the interior. 



In the department of the Aube, not far from Lezig- 

 nan, the Tithymalis (Euphorbia helioscopa) grows abun- 

 dantly,, and the natural guest of this plant is a Sphynx. 

 While this sphynx is still a caterpillar, a dipterous 

 tachinaria takes possession of it to feed her young 



