156 ' ON THE ICHNEUMON FLY. 



grub or caterpillar on which they have existed dies, or perhaps just retains 

 sufficient vital power to turn into a chrysalis, which at last does not give 

 birth to a moth, butterfly, or any other fly proper to it; but to one or more 

 full-grown Ichneumons, whose larvas have become pupae within this case. 

 The author, not many years ago, had a chrysalis which disclosed at the 

 proper time, no less than seventeen Ichneumons, instead of a large moth 

 which he had expected to see emerge from it. Instinct, we are told, upon high 

 authority, is a propensity prior to experience, and independent of instruction : 

 it is verified in these strange operations. The little maggot which springs 

 from the egg of the Ichneumon goes on eating up its prey, devouring every 

 part of it except the vital organs, which it never touches, as if it knew 

 instinctively that the death of its victim would involve its own entire destruction 

 by famine. Some Ichneumons only glue their eggs to the bodies of certain 

 larvae, because their maggots are provided with instruments for piercing the 

 skin. Others, like the Cuckoo among birds, lay their eggs in the nests of 

 insects, which hatch them to. devour their own young. Bees are particularly 

 subject to such insidious enemies. No concealment, unless perhaps under 

 water, seems sufficient to baffle an Ichneumon, and nothing can surpass its 

 perseverance until its eggs are safely placed in the condition suitable to its 

 progeny." 



The following would seem easy of proof to all persons. In regard to 

 Ichneumon tipulae, now called Platygaster tipulge, Mr. Sidney says, ^'This 

 little Platygaster may be readily found on the glumes of the wheat plants, 

 in the. months of July and August. It runs rapidly over the ears, and 

 seems to know well which are those occupied by the larvae of the midge. 

 The author found numbers of them in various wheat-fields in August, 1845; 

 and almost invariably, on examining the ears on which they appeared, discovered 

 that they contained the objects of their search. The Ichneumon hunts for 

 them with the utmost eagerness, and by the aid of a sharp tail places a 

 single egg in each of their bodies. The sight has been witnessed by Kirby, 

 by the following experiment: — A number of larvae of the wheat midge were 

 put upon a piece of white paper, pretty near each other, and an Ichneumon 

 was dropped into the midst of the group. The energy of her manner, the 

 rapid vibrations of her antennae, and the whole of her attitudes, were most 

 amusing. On approaching one of the larvae her agitation quickened to the 

 utmost intensity; she soon bent her body in a slanting direction beneath her 

 breast, applied her tail to the larva, and, becoming still as death, sent forth 

 her curious sheath and deposited her egg in the victim, which writhed con- 

 siderably under the operation. If she came to one that had previously an 

 egg in it, she left it in an instant, and sought another, for the Platygaster 

 lays but one in each. This, however, often repeated, destroys a great many 

 of these devastators of the grain." 



Each .species of Ichneumon is restricted in its attacks to one, or at most 

 to a few, particular species oF caterpillars. IMr. Stephens states that he possessed 



