Russel Wallace : Alfred Russell Wallace (sic)
Among the more remarkable forms in the first-named order are the Psychidæ, small moths the females of which are not only without wings, but have neither legs nor antennæ. The female Psyche is, in fact, a mere helpless egg-bag, which never quits the case or covering in which it was bred. The males are small delicate moths with bodies covered with long silken hairs, and with dusky semi-transparent wings. The larvæ live in cases made of silk or vegetable tissue, bits of straw, stick, or leaves, and they carry these cases just as snails do their shells.
The ravages of the Tineidæ and the curious cases of Coleophora and Gelechia are illustrated by figures after Stainton; while the cut on p. 331 represents the beautiful pink or violet net-work cocoons in which some Brazilian species suspend themselves by slender threads.
The parasitic Hymenoptera forming the families Ichneumonidæ, Chalcididæ, and Proctotrupidæ are well described, and a quotation from this chapter will exhibit the style in which the book is written:--
"These parasites are very pretty and elegantly-formed insects when in the adult form, and are gifted with great agility and restlessness; but in their early condition they cannot move, having no locomotive organs, and their structures are so soft that they are destroyed with the greatest ease. The larvæ look like worms or maggots, and do not attain a great perfection of development during their growth. All the parasites seek out a caterpillar, a larva, or an insect which suits their purpose, in order to lay an egg within its body. The larva which is born from this egg is nourished by the blood and fat of the victim, whose vital organs it does not touch or injure in any way; for were it to die, the parasite would come to 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 unfortunate insect, and undergoes its transformation. The skin of the victim protects some of the pupæ of its destroyers after all the inside has been eaten. Nearly all, if not quite all, insects are subject to the attacks of parasitic Hymenoptera. 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 [[p. 330]] it never reaches the stage of growth when it can lay eggs or reproduce its kind, for before this time the growing larvæ within destroy it, as it were, by slow consumption. Some affected caterpillars die soon, others nearly reach their full growth, and a few undergo their transformation 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 Hymenoptera that had been living within the chrysalis he has been keeping."
One of the most curious recent discoveries among beetles is that which was published by Schiödte, in 1864, of viviparous Staphylinidæ. These are about the tenth of an inch long, and are found in the nests of the Termites of Brazil. They are distinguished by the swollen development of the abdomen, which is carried in a most peculiar manner, being turned up and allowed to rest on the back of the insect. The enormous distension of this part of the body is due to the fact that the beetles do not lay eggs, but produce living larvæ, and they are the only beetles that do so. It is supposed that the hairs which cover some parts of the abdomen are furnished with a peculiar secretion that is liked by the white ants among which they live.
The extraordinary economy of many of the Diptera or flies is exhibited in a variety of beautiful cuts, one of the best of which represents the metamorphoses of Stratiomys chameleo. This fly frequents flowers in order to prey upon other insects, but its larva lives in stagnant water, and is a long, hard-skinned creature, whose small head is furnished with two minute hook-like mandibles. The terminal segments of the body are gradually narrowed, and can be elongated like a sliding telescope, and the slender extremity terminates in two small orifices crowned with hairs. This larva swims about in shallow water, and when it wants to breathe it sticks up the end of its body and respires through the two small holes at the apex. When the larva is mature it floats on the surface, the pupa being formed within the skin, which serves at once as a cocoon and as a boat, from which in due time the brightly coloured and active fly escapes to its aërial existence.
[[p. 331]] In the last chapter a short but clear account is given of the recent discoveries as to the metamorphoses of Crustacea, from the works of Spence Bate, Fritz Müller, Darwin, and others.
In the original work reference is chiefly made to common French or Continental insects, some of which are natives of our own country, while many are not found here. In adapting the work for English readers, it would have been well to have stated in every case whether the insect mentioned was an English one. The great carpenter bee (Xylocopa violacea), for example, is described as "not uncommon;" but the reader is not told that, although common in France, it is unknown in England. More simple and familiar language might also have been occasionally used; but these are small defects in so useful and attractive a work, which is just the thing for a present to an intelligent and inquiring country schoolboy.
Alfred R. Wallace
1. "The Transformations or Metamorphoses of Insects (Insecta, Myriapoda, Arachnida, and Crustacea)." Being an adaptation for English readers of M. Emile Blanchard's "Metamorphoses, Mœurs, et Instincts des Insectes." By P. Martin Duncan, F.R.S., Professor of Geology in King's College, London. (Cassell, Petter, and Galpin ) [[on p. 329]]