This section is from the book "General Outline Of The Organization Of The Animal Kingdom, And Manual Of Comparative Anatomy", by Thomas Rymer Jones. Also available from Amazon: A General Outline of the Animal Kingdom and Manual of Comparative Anatomy.
(809). We have already seen that the Flea or the Grasshopper will spring two hundred times the length of its own body; that the Dragonfly possesses such indomitable strength of wing, that for a day together it will sustain itself in the air, and fly with equal facility and swiftness backwards or forwards, to the right or to the left, without turning; that the Beetles are encased in a dense and hard integument, impervious to ordinary violence; and we might add that the Wasp and the Termite Ant will penetrate with their jaws the hardest wood. Neither is the velocity of the movements of insects inferior to their prodigious muscular power. "An anonymous writer in Nicholson's Journal," say Kirby and Spence, "calculates that in its ordinary flight the common House-fly (Musca domestica) makes with its wings about six hundred strokes, which carry it 5 feet, every second; but if alarmed, he states their velocity can be increased six- or seven-fold, or to 30 or 35 feet in the same period. In this space of time a race-horse could clear only 90 feet, which is at the rate of more than a mile a minute. Our little Fly, in her swiftest flight, will in the same space of time go more than the third of a mile.
Now, compare the infinite difference of the size of the two animals (ten millions of the Fly would hardly counterpoise one racer), and how wonderful will the velocity of this minute creature appear! Did the Fly equal the race-horse in size, and retain its present powers in the ratio of its magnitude, it would traverse the globe with the rapidity of lightning*".
* Kirby and Spence, op. cit. vol. ii. p. 358.
(810). Let the reader, therefore, imagine for an instant that great law of nature, which restricts the dimensions of an insect within certain bounds, dispensed with even in a single species. Suppose the Wasp or the Stag-beetle dilated to the bulk of a tiger or of an elephant - cased in impenetrable armour - furnished with jaws that would crush the solid trunk of an oak - winged, and capable of flight so rapid as to render escape hopeless; what would resist such destroyers? or how could the world support their ravages?
(811). Such is the comparative strength of insects. Let us now proceed to examine the muscles to which it is owing, their structure and general arrangement.
(812). The muscles consist of bundles of delicate fibres, that arise either from the inner surface of the segments composing the skeleton, or else from the internal horny septa which project into the thorax. The fibres themselves are of a white or yellow colour; and so loosely are they connected by cellular tissue, that they may be separated by the slightest touch.
(813). All the muscles of an insect may be arranged in two great divisions: the first including those that unite the different segments of the body; the second, those appropriated to the movements of the limbs, jaws, and other appendages. The former are entirely composed of fleshy fibres; the latter are provided with tendinous insertions, by which their force is concentrated and made to act with precision upon a given point of the skeleton.
(814). The connecting muscles are generally arranged in broad parallel bands, arising from the inner surface of a given segment, and passing on to be inserted in a similar manner into another segment, so that by their contraction the cavity in which they are lodged is diminished by the approximation of the different rings: these have no tendons.
(815). The locomotive muscles, of course, take their character from the joints of the limb upon which they act; and as we have already seen that these movements are generally confined to those of a hinge, the muscular fasciculi may be conveniently grouped into two great classes - the flexor muscles, that bend the joint, and the extensors, by which it is again straightened, and brought back to its former position. This simple arrangement will be best understood by an inspection of fig. 154, representing the muscles of the leg of a Cockchafer (Melo-loniha vulgaris), as they are depicted by Straus-Durckheim*. In the thigh, for example, there are two muscles, one of which bends, the other straightens, the tibia. The flexor (fig. 154, a) arises from the lining membrane of the femur, and is inserted by a tendon into a process of the tibia in such a manner as to flex the leg upon the thigh; while its antagonist (6), attached to a process derived from the other side of the joint, has an opposite effect, and by its contraction extends the leg.
* Considerations generates sur l'Anatomie comparee des Animaux articules, aux-quelles on a joint l'Anatomie descriptive du Hanneton. 1 vol. 4to. Paris, 1828.
In the tibia there are likewise two muscles, so disposed as to move the entire tarsus and foot.
The extensor (f) of the tarsus is the smallest; it arises from the lower half of the interior of the tibia, and is inserted into the margin of the first joint of the tarsus: but the flexor of the foot (c), arising from the upper half of the cavity of the tibia, ends in a delicate tendon, which passes through all the tarsal segments, to be fixed to the flexor tendon of the claw-joint, upon which it acts; and as it traverses the penultimate joint it receives the fibres of an accessory muscle (d.) The extensor of the claw (e) is likewise placed in the penultimate tarsal segment, and strikingly exhibits, by its small comparative size, the feebleness of its action when compared with that of the flexors of the same joint.
(816). It would be superfluous to describe more in detail the disposition of individual muscles, as the above example will abundantly suffice to give the reader an idea of the general arrangement of the muscular system, not in insects only, but in all the Artictjlata provided with jointed extremities.
(817). The substances employed as food by insects are various, in proportion to the extensive distribution of the class. Some devour the leaves of vegetables, or feed upon grasses and succulent plants; others destroy timber, and the bark or roots of trees; while some, more delicately organized, are content to extract the juices of the expanding buds, or sip the honeyed fluids from the flowers. Many tribes are carnivorous in their habits, armed with various weapons of destruction, and carry on a perpetual warfare with their own or other species; and again, there are countless swarms appointed in their various spheres to attack all dead and putrefying materials, and thus to assist in the removal of substances which, by their accumulation, might prove a constant source of annoyance and mischief. Such differences in the nature of their food demand, of course, corresponding diversity in the construction of the instruments employed for procuring nourishment; and accordingly we find, in the structure of the mouths of these little beings, innumerable modifications adapting them to different offices.