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THE HYMENOPTERA. 1 85 



an end also. It is only when the larva is nearly full grown, and is 

 about to undergo its metamorphosis into a pupa, that it appears 

 to know that the life of the victim is not likely to be of much 

 further use. It then devours the internal organs of the unfor- 

 tunate insect, and undergoes its transformation. The skin of 

 the victim protects some of the pupae of its destroyers after 

 all the inside has been eaten. 



Nearly all — if not quite all — insects are subject to the attacks 

 of parasitic Hynienoptcra. Fine, smooth, and brightly-coloured 

 caterpillars often have a black spot upon their skin, and this is 

 the healed wound of the ovipositor of one of the parasites. 



Sooner or later the creature is sure to die, and it never reaches 

 the stage of growth when it can lay eggs or reproduce its kind, for 

 before this time the growing larvae within destroy it, as it were, by 

 a slow consumption. Some affected caterpillars die soon, others 

 nearly reach their full growth, and a few undergo their transforma- 

 tion into the chrysalis state before death. It is, therefore, not an 

 uncommon thing for a butterfly collector, who hopes to see a fine 

 moth disengage itself from its pupal covering, to be disappointed 

 by the appearance of several little parasitic Hymcnoptera that 

 have been living within the chrysalis he has been keeping. 



Although we know a great deal about the economy of the 

 parasitic Hynienoptera, still there are some points of the greatest 

 possible interest in it, and which are really very provocative of 

 wonder. When a parasitic insect of this family discovers a cater- 

 pillar feeding on a leaf in broad daylight, there is nothing very 

 wonderful about it, because we could do as much ourselves ; but 

 when it is evident that the female parasitic Hymenoptera finds out 

 a larva which is situated inside a fruit, and within a branch or 

 trunk of a tree, and perfectly out of sight, we may well wonder 

 how this is done. When one sense fails, another is supposed to 

 supply its place, and the sense of smell of the insect is thought to 

 do what the eyes evidently cannot perform. It is probable that the 

 sense of hearing may assist in the discovery, but it is by no means 

 proved. There is another instinct which is very remarkable, and, 

 indeed, as curious as that just mentioned. A large parasite deposits 

 only one ^^^ under the skin of a caterpillar or other insect, for 

 its larva, as it increases in size, requires all the juices of the 



