74 METAMORPHOSES OF MAN 



To this group the Ichneumonidse belong, — those 

 insects which, by destroying other species in thou- 

 sands, effect so much for our gardens, fields, and 

 plantations, — benefits which we fancy very few are 

 aware of. We shall study one of these insects, 

 whose history can hardly be separated from that of 

 the cabbage butterfly, and which has engaged the 

 attention of Goedaert, Swammerdam, Vallisnieri, and 

 Keaumur. It is called the glomerate microgaster 

 (Microgaster glomeratus). 



This insect is like a small fly, and has four wings 

 supported on nervures whose interspaces are large, a 

 black body, yellow legs, and antennae which are kept 

 in constant motion. The female carries within the 

 posterior portion of the abdomen, a lancet, or hollow 

 sting (ovipositor), composed of three distinct pieces, 

 whose function we shall now explain. 



When she is about to deposit her eggs, she looks 

 out for the caterpillar of the Pieris; as soon as she 

 has found it, she settles down upon it, and grasping it 

 tightly by the back, she pierces its skin with a single 

 stab of this instrument, whose three component parts 

 constitute a sort of hollow tube. She next drives it 

 more deeply into the substance of the body, and at 

 the same moment an egg escapes from the ovary, and, 

 gliding down this canal, is deposited in the tissues of 

 the caterpillar. The Microgaster then draws back its 

 ovipositor, advances a little, and recommences this 

 performance. In vain does the poor caterpillar writhe 

 at every successive puncture ; its enemy continues the 

 operation in the calmest manner possible, and never 

 gives over till it has effected its purpose, and deposited 

 from forty to fifty eggs in places of safety. This 



