Objects for the Microscope. 115 



ICHNEUMON-FLY. 



(Pachymerus calcitrator.) 



Always have several of these in your collection ; they are 

 beautiful and most interesting ; they have been appointed 

 to do a certain work, they have been gifted with wonderful 

 instinct, and provided with fit instruments to perform it, 

 and they are one of our many examples of obedience to the 

 order of God, which we would do well to pause and con- 

 sider. This little unheeded fly, watch for it and learn its 

 habits ; examine it here as it is prepared for you. 



It was black and reddish, with brown edging, and white 

 lines across the segments of the abdomen. This we cannot 

 see here ; but we can see the antennae, its first needful in- 

 strument for work, with twenty-two joints, each with a 

 bristle inside, the wings large, transparent, and iridescent, 

 the stigma yellowish-brown, the one marginal cell elongated. 

 (Compare it with the wing of Cypheus, which has two 

 marginal and four sub-marginal cells) and one sub-marginal 

 large cell, with a little nerve running into it. The thighs 

 are thick, and the tibiae spurred. 



They abound often on Umbellifer&e. 



And this is its use in the world : to find out the larvae 

 of Cypheus pygmceus, wherever it may be, and destroy it by 

 laying one of its own eggs inside its body, which, when 

 hatched, will feed upon the fat of the destroying insect, 

 and finally kill it, by preventing its further development. 

 Now, considering that the Saw-fly maggot is carefully con- 

 cealed in the wheat-stalk, the work is not so easy ; for the 

 stem must be pierced at precisely the spot where it lies, and 

 the Ichneumon must ascertain that no other fly has pre- 

 ceded her, or the life of her own offspring will fail. 



The antennae ascertain this for her ; they vibrate inces- 

 santly as she runs rapidly up and down every stem, and 

 whether they hear the gnawing of the little maggot within, 

 or feel the consequent vibration, or smell the larva through 

 the pores of the stomata I cannot tell ; but it may be 

 that it by all these finds out the precise spot, and then with 

 its long ovipositor, which is barbed and works like an auger, 



