While there are according to this definition numerous insect species on Amaterasu, all are small, and the larger species are more properly called insectoid (by "large", we mean mouse-size or greater). Insects on Amaterasu come in a wide variety of shapes: some with one body part, some with three or four, most with at least six legs, ranging up to one curiosity with 18 legs. Among the larger species, one encounters only creatures with 2 body parts or with three, while number of legs varies between six and eight.
All the insectoid species, including the machi, have compound eyes, lay eggs and have only a limited ability to self-regulate their internal temperature. Only the smaller representatives of the species have true exoskeletons, but all the insectoid species have true lungs (by which we mean a collection of sacs connected at a single point to a windpipe or other common opening to the outside). Their circulatory systems are a hybrid: within the major body cavities, fluids flow freely, bathing the major internal organs, but the lungs, musculature and brain are laced with arteries and veins, through which the internal fluids are pumped by several simple hearts distributed along the circulatory routes.
The larger insectoids, including the machi, have also evolved a mixed skeletal system. The entire body is covered with a thin, flexible collagenous sheath, much like skin in function. Beneath this layer, the major body segments are housed in keratinous exoskeletal frames, but the frames are laced through with struts, arches and reinforcing ribs, creating light but strong structures able to support the weight of these larger animals. Internal organs hang from these reinforcers. The shafts of the limbs are also exoskeletal, but where they meet the joints, the exoskeleton "dives inward" as it were, and becomes an endoskeletal joint, covered by the collagenous skin, which seamlessly envelopes the body. In the case of the machi, this structure extends into the entire hand.
The insectoid lungs have generally six lobes, arranged symmetrically in pairs around a central tracheal tube. In many species, the windpipe travels for some distance from the lungs before exiting the body. There are two main phyla of insectoids, the "mantoid" (with three body parts) and the "beetloid" (with two body parts). Among the beetloids, respiration is driven by muscles attached to the top of the shell. Among the mantoids, the lungs are located in the thoracic segment, but they are inflated by the abdomen. The abdomen of these creatures can expand and contract because the underside is not a solid shell, but is divided into interlocking plates; muscles force these plates closer or further apart. The negative pressure in the internal fluids created by the expansion of the abdomen inflates the lungs, which float in a fluid cavity in communication with the abdominal cavity, although they are supplied with their own blood vessels.
Insectoid eyes are compound, with from 42 to 206 segments. The machi have 134 segments per eye, and research has revealed some interesting facts. Although we have always pictured insect sight as being fractured, since their eyes are, sort of like a kaleidoscope view of the visual field, interviews with the machi indicate that they, at least, see a visual field little different from our own. Apparently the brain integrates the separate images from the lenses into a whole. Moreover, all the lenses of the compound eye do not have the same focal length, and a machi can "focus" its vision on objects near or far simply by selecting (unconsciously, of course) the lenses with appropriate focus. There also seems to be a sort of "synthetic aperture" effect at work: if no set of lenses has the right focal length, the brain can select several that come close, and then synthesize their images into a clear, focussed picture. This has serious implications for our understanding of terrestrial insect sight, as well.
Having given a general picture of the insectoids of Amaterasu, we now turn our attention to the machi in particular. The machi are of the mantoid type, about a meter to a meter and a half long, yellowish in color with brown and red highlights. When they stand normally, on four limbs, they are about a third of a meter off the ground. They can stand on only their lower limbs, although they cannot walk that way, and then their heads are about a meter high.
The machi have triangular heads, a narrow thorax, large abdomen, and six limbs. Unlike a terrestrial mantis, their limbs are thick and strong. The mouth resembles that of a parrot, or a turtle. The head is about the size of an average pumpkin and has delicate patterns that are a mark of beauty to the machi. The compound eyes sit at the top of the head, to each side (as in the terrestrial mantis), and are black and about the size of a softball. They are more tear-drop shaped than round.
The machi hand is the most refined grasping instrument on the planet. The hand itself is exoskeletal, shaped like a narrow, three-sided pyramid. The apex of the pyramid attaches to the arm at the wrist. The underside of the base of the pyramid is sculpted and padded and serves as the palm of the hand. The four fingers are all endoskeletal, with soft, sensitive tips. They attach to the hand along one of the edges of the base of the pyramid, at the palm. This edge is oriented as the top of the hand. The three thumbs are similar in structure to the fingers. One thumb is located at the lower corner of the base of the hand, where the two edges of the pyramid without fingers come together. The other two thumbs are located on these edges, clustered near the middle thumb. When the hand grasps something, the tips of the thumbs smoothly meet the fingers, resting in the gaps between each finger. The object grasped can rest within the "cage" thus formed, with its lower end resting on the palm, if needed.
Only the upper pair of arms have this type of hand. The middle and lower pairs of limbs have simplified versions, with broader and fatter pyramids, shorter digits, and only 2 thumbs and 3 fingers. Nevertheless, the middle limbs are often called into service to supplement the main hands. The lower limbs are used exclusively for support.
The sound-producing apparatus of the machi is remarkable. The machi have six-lobed lungs, arranged in pairs around a central tracheal tube. They are located in the thorax, and are inflated and deflated by the expansion and contraction of the abdomen, as in all mantoids. The lungs and trachea are oriented forward, towards the head. At the top of the trachea, near the neck, the trachea makes a sharp U-turn, to meet the windpipe. The bend of this U contains the epiglottis, with the glottal flap. The muscles of the epiglottis allow the machi to shorten or lengthen this bend slightly. The windpipe itself is part of the thoracic exoskeleton, a hollow tube about a centimeter in diameter which runs longitudinally down the middle of the underside and issues out an opening tucked under the bottom edge of the thorax. Along the windpipe are seven small openings, or stomae, which are normally closed by annular valves. Scientists speculate that the glottal flap was used by the early machi to close off the lungs as they foraged in the shallow seas and marshes, as is the case with several species to this day. The stomae are clearly used to provide more oxygen during times of exertion.
Machi produce speech sounds (actually musical tones) by partially closing the glottis. During respiration, the glottis vibrates the air column within the windpipe, and this produces a tone. The sound thus produced is not crisp and light, like a flute, but warm and rich, like a clarinet. Various combinations of open and closed stomae are used to modify this base tone into different pitches. By tensing or relaxing the muscles of the epiglottis, each pitch can be varied slightly, which the machi do to bring their individual sound instruments into closer harmony.
The machi are not alone in possessing at least some of these structures. For example, the Red Racer, a carnivorous predator of the mantoid type, has similar stomae, which are even more numerous and larger than the machis', for extra energy when running down their prey, but they have no epiglottal flap, and so are mute. The Fungus Rooter, a beetloid the approximate size of a cow and shaped like a tortoise, has an epiglottal flap and a very long windpipe, but no stomae, so it can produce only one bass note, a deafening blast it uses to signal danger or call to the herd. Many other species have some or another of these features and produce sounds. The jungles and marshes of Amaterasu are alive with whistles, honks and twitters.
We have touched only on machi physiology in this paper. Machi culture and society are fascinating topics, but beyond the scope of this article.
© 1997, Terrence Donnelly