M. Plateau has studied the power of traction in some insects, the power of pushing in the digging insects, and the lifting power of others during flight. He has thus been able to make some most interesting comparisons, of some of which we will relate the results.

The average weight of man being 142 lbs., and his power of traction, according to Regnier, being 124 lbs., the proportion of the weight he can draw to the weight of his body is only as 87 to 100. With the horse the proportion is not more than 67 to 100, ahorse 1,350 lbs. in weight only drawing about 900 lbs. The horse, therefore, can draw little more than half his own weight, and a man cannot draw the weight of his own body.

This is a very poor result, if compared with the strength of the cockchafer. This insect, in fact, possesses a power of traction equal to more than fourteen times its own weight. If you amuse yourself with the children's game of making a cockchafer draw small cargoes of stones, you will be surprised at the great weight which this insignificant-looking animal is able to manage.

To test the power of traction in insects, M. Plateau attached them to a weight by means of a thread fastened to one of their feet. The Coleoptera (Beetles) are the best adapted for these experiments. The following are some of the results obtained by the Belgian physician:— Carabiis auratus can draw seven times the weight of its body; Nebria brevicollis^ twenty-five times; Necrophorus vespillo^ fifteen times; Trichius fasciatiis, forty-one times; and Oryctes nasicornis, four times only. The bee can draw twenty times the weight of its body; Donacia nyinphea * forty-two times its own weight.

A beetle. —Ed,

From this it follows that if the horse possessed the same strength as this last insect, or if the insect were the size of a horse, they would either of them be able to draw 56,700 lbs. M. Plateau has ascertained the pushing power in insects, by introducing them into a pasteboard tube, the interior of which was made rough, and in which was fixed a glass plate, which allowed the light to penetrate into the prison. The animal, if excited, struggled with all its strength against the transparent plate, which, on being pushed forward, turned a lever adapted to a miniature dynamometer, which indicated the amount of effort exercised. The results thus obtained prove that the pushing power, like the power of traction, is greater in inverse proportion to the size and weight of the animal. A few figures will better explain this curious law. In Orydes naskornis the proportion of the pushing power to the weight of the insect is only three to two; in Geotrupcs sferco-rarius it is sixteen to two; and in Onthophagus niickicornis seventy-nine to six.

Experiments have been made on the lifting power of insects by fastening a ball of soft wax to a thread attached to the hind legs. The proportion of the weight lifted has been found equal to that of the body. That is to say, the insect when flying can lift its own weight. This is proved by the following calculations:— In the Neuroptera the proportion is i in the Dragon-fly {Libellu/a vulgata)^ •7 in Lestes sponsa. In the order Hymenoptera it is 78 in the bee, and •63 in Bombus terrestris, the humble-bee. In the Diptera it is •9 in CaUiphora vomitoria* 1-84 in the Syrphus corollce^ and 177 in the house-fly. These results show that insects have only sufficient power to sustain their own weight when flying, as the above calculations exhibit the maximum of which they are capable, and at the utmost this strength would only compensate for the fatigue occasioned by the action of flight. At the same time it is to be observed that the Diptera, and among others the house-fly, can sustain their flight longer than the Hymenoptera and Neuroptera, although one would not think so from their appearance. In conclusion, if an insect's power of flying is not considerable, its power of traction and propulsion are immense, compared with the vertebrate animals; and, in the same group of insects, those that are the smallest and lightest are the strongest. The proportion between the muscular strength of insects and the

The meat-fly. — Ed.

INTRODUCTION. 2$

dimensions of their bodies, would not appear to be on account of their muscles being more numerous than those of vertebrate animals, but on account of greater intrinsic energy and muscular activity. The articulations of insects may be considered as solid cases which envelop the muscles, and the thickness of these cases appears to decrease in a singular manner according to the size of the creature. The relative bulk of the muscles being less in the smaller species than in the larger, it is necessary to explain the superior relative strength of the former by supposing them to possess a greater amount of vital energy. These astonishing phenomena will perhaps be better understood if we consider the obstacles which insects have to overcome to satisfy their wants, to seek their food, to defend themselves against their enemies, &c. To meet these requirements they are marvellously constructed for both labour and warfare, and their strength is superior to that displayed by all other animals. It is also much greater than that of the machines we construct to replace manual labour. They represent

strength itself God's workmen are infinitely more powerful than those invented by the genius of man, which we call machines.

We think it necessary, in closing this chapter, to give a sort of general outline of the great class of animals which we are about to study. If we wished to characterise insects by their exterior aspect, we might consider them as articulate animals, whose bodies, covered with tough and membranous integuments, are divided into three distinct parts: the head, provided with two antennae, and eyes and mouth of very variable form; a trunk or thorax, composed of three segments, which has underneath it always six articulated limbs, and often above it two or four wings; and an abdomen, composed of nine segments, although some may not appear to exist at first sight.

If, in addition to these characteristics, one considers that these animals are not provided with interior skeletons — that their nervous system is formed of a double cord, swelling at intervals, and placed along the underside of the body, with the exception of the first swellings or ganglions which are under the head — that they are not provided with a complete circulating system — that they breathe by particular organs, termed tracheae, extending parallel to each other along each side of the body, and comnmnicating with the exterior air by lateral openings termed spiracles — that their sexes are distinct — that they are reproduced from eggs — and, in conclusion, that the different parts we have mentioned are not complete until the creature has passed through several successive changes, called metamorphoses,

a general idea may be formed of what is meant in zoology by the word "insect." Insects, whose general organisation we have briefly traced, have been classed by naturalists as follows:—

Aptera (Fleas and Lice). 2. DiPTERA. (Gnats, Flies, &c.) 3. Hemiptera (Bugs, &c.) 4. Lepidoptera (Butterflies and Moths). 5. Orthoptera (Grasshoppers, Crickets, Cockroaches, &c.) 6. Hymenoptera (Bees, Wasps, &c.) 7. Thysanoptera ( Thrips cerealuim). 8. Neuroptera {Libellula, or Dragon-lly; Ephemera^ or May-fly; Phryganea, or Alder-fly). 9. Coleoptera (Beetles).

We shall commence the history of the various orders by examin ing the Aptera.

APTERA.

Insects of this order are without wings, and the name is derived from two Greek words, a, privative, and irrephv, wing, indicating the negative character which constitutes this order.* It consists of Fleas and Lice. The Flea (Fu/ex), of which De Geer formed a separate group, and called Suctona, includes several species.

The common flea {Fiilex irrifans, Fig. 17) has a body of oval form, somewhat flattened, covered with a rather hard horny skin of a brilliant chestnut brown colour. It is the breaking of this hard skin which produces the little crack which is heard when, after a successful hunt, one has the happiness to crush one of these parasites between one's nails. Its head, small in proportion to the body. Fig. 17. is compressed, and carries two small antennae, ^'^* {Puiex tmtans).of cylindrical form, composed of four joints, which the animal shakes continually when in motion, but which it lowers and rests in front of its head when in a state of repose. The eyes are simple, large, and round. The beak is composed of an exterior jointed sheath, having inside it a tube, and carrying underneath two long sharp lancets, with cutting and saw-like edges. It is with this instrument that the flea pierces the skin, irritates it, and causes the blood on which it lives to flow.

This bite, as every one knows, is easily recognised by the presence of small darkish red spots, surrounded by a circle of a paler colour.

It is probable that one day the order Aptera will be superseded. The absence of wings is not really a character of great value. De Blainville, Mollarcl, Pouchet, Van Beneden, and Gervais, have made several attempts in that direction. The fleas have been placed among the Diptera, and the lice among Ilemiptera in the " Traits de Zoolojjie Medicale " of the two last authors.

The quantity of blood absorbed by this little creature is enormous, when compared with its size.

The body of the flea is divided into thirteen segments, of which one forms the head; three the thorax, which is short, and the remainder the abdomen. The Hmbs are long, strong, and spiny. The tarsus or foot, has five joints, and terminates in hooks turned in opposite directions. The two anterior limbs are separated from the others, and are inserted nearly under the head; the posterior ones are particularly large and strong. The jumps which fleas are able to make are really gigantic, and the strength of these litde animals quite herculean, when compared with the size of their bodies. The reader may be inclined to smile at the assertion that the flea possesses herculean strength; but let him wait a little, and he will find that it is no exaggeration.

To give some idea of the strength, the docility, and the goodwill of the fleas, some wonderful little things have been made, which have served at the same time to show the astonishing skill of certain workmen.

In his " Histoire abrege'e des Insectes," published in the seventh year of the French Republic, Geoffroy relates that a certain Mark, an Englishman, had succeeded, by dint of patience and art, in making a gold chain the length of a finger, with a padlock and a key to fasten it, not exceeding a single grain in weight. A flea attached to the chain pulled it easily. The same learned writer relates a still more surprising fact. An English workman constructed a carriage and six horses of ivory. The coachman was on the box, with a dog between his legs, there were also a postillion, four persons in the carriage, and two servants behind, and the whole of this was drawn by one flea.

In his " Histoire Naturelle des Insectes Apteres," Baron Walck-enaer relates the following marvellous instance of industry, patience, and dexterity:— " I think it is about fifteen years ago, that the whole population of Paris could see the following wonders exhibited on the Place de la Bourse for sixty centimes. They were the learned fleas. I have seen and examined them with entomological eyes, assisted by a

glass. "Thirty fleas went through military exercise, and stood upon their hind legs, armed with pikes, formed of very small splinters of wood. " Two fleas were harnessed to and drew a golden carriage with

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