Antenna (entomology)

“ Third segment of the antenna with five divisions (fig. 161b) .
g. Third segment of the antenna not furnished with a tooth or distinct angular projection.
h. Body covered with metallic scales; front of female of normal width; front and middle tibiæ greatly dilated. L. lepidota. Lepidoselaga Macq.
hh. Body without metallic scales; antennæ not very long, the third segment not cylindrical, not situated on a projecting tubercle; front of the female narrow. South. D. ferrugatus. (= Diabasis) Diachlorus O. S.
gg. ”

“ In the female of the Stylopidæ the thorax loses all traces of segments, and is fused with the head, and the abdominal segments are faintly marked, losing their chitin.
While the maxillæ have several joints, the mandibles are 1–jointed, but there are traces of two joints in Campodea, certain beetles, etc. In the antenna there is a great elasticity in respect to the number of joints, which vary from one or two to a hundred or more. It is likewise so in the thoracic legs, where the number of tarsal joints varies from one to five ”

“ This specimen is taken from a male insect, and the reader will find his trouble repaid on mounting one of these antennæ as a permanent object.
Fig. 12 is an antenna from one of the common ground beetles (Cárabus) looking like a string of elongated pears, from the form of the joints. The reader will see that in beetles he is sure to find eleven joints in the antennæ.
Fig. 10 is the entire antenna of a fly (Syrphus) , one of those pretty flies which may be seen hovering over one spot for a minute, and then darting off like lightning to hang over another. ”

“ The majority of flies have antennae of another form, peculiar to the Order, viz. three segments, the outer one of which is of diverse form, according to the genus or species, and bears on its front a fine projecting bristle, frequently feathered, as in Fig. 213, F; and often distinctly divided into two or more joints. This form of antenna is found in the series Aschiza and Schizophora; it is well exemplified in the common house-fly, where the organs in question hang from the forehead, and are placed in a hollow formed for their reception on the front of the head. ”

“ The antennae are long, delicate and threadlike, and must be broken very easily in the flight of the moth. It is nothing unusual to see them with one antenna shorter than the other, half, or entirely gone; and a perfect specimen with both antennae, and all the haif on its shoulders, is rare. They have a long tongue that uncoils like Lineata, and Celeus, so they are feeders, but not of day, for they never take flight until evening, except when disturbed. The male is smaller than the female, his fore-wings deeply flushed with darker colour and the back brighter red with more black in the bands. ”

“ Theory is fascinating, but with the slight data at command, it is hardly profitable. Observation shows that the wasp instinctively flies toward the light; its course is also materially affected by currents of air, such as draughts in a room where it is held captive. Mechanical response to these two influences will, in this case, usually serve to liberate it without the use of any other sense or faculty. Again, the antennae seem to play an important rôle in orienting the insect. Accidental loss of one antenna in one case retarded the finding of the nest. ”

“ In the female there are fifteen segments, each bearing a ring of hairs, but of small and disproportionate size, whereas in [Pg 50] the male the bushy character of the hairs is conspicuous even to the naked eye. In fact, it is the easiest criterion for judging the sex of the insect. At the base of the first joint of the male antenna is a deep cup-shaped structure packed with sense organs, and containing a large nerve ganglion. There are sixteen segments in the whole antenna, one more than in the female. ”

“ I tethered, for instance, a large specimen of Formica ligniperda with a fine thread to a board, and when she was quite quiet I approached a scented camel's-hair pencil slowly to the tip of the antenna, which was at once withdrawn, though the antenna took no notice of a similar pencil, if not scented. ”

“ A very simple method of finding them in a spirit specimen is to take the insect between the thumb and index finger of the left hand, holding it up to the light in such fashion as to keep the first pair of legs well clear of the head. Then, with a needle held in the right hand, raise the thorax till it lies in the same plane as the body. Each antenna lies in a groove beneath the eye. Gentle manipulation with the needle will lift them out, so that they may be clearly seen, not only with the hand magnifier, but with the unassisted eye. ”

“ The ants spend much time in grooming the forelimbs, antennae and other parts of the body. Regardless of how dusty an ant may become momentarily, it keeps its antenna immaculate by drawing it through its mouth and licking and cleansing it. ”

“ Some writers say the antennae are the seat of scent, touch, and hearing. I had not thought nature so impoverished in evolving her forms as to overwork one delicate little organ for three distinct purposes. The antennae are situated close where the nose is, in almost every form of life, and I would prefer to believe that they are the organs of scent and feeling. I know a moth suffers most over any injury to them; but one takes flight no quicker or more precipitately at a touch on the antennae than on the head, wing, leg, or abdomen. ”

“ Appendages.—Many specimens have two slender, short-jointed antennæ projecting out from in front of the carapace (fig. 2, pl. 27) . Others show a second shorter, smaller pair that is nearer the median line and probably represents the antennules. Several specimens have two or three very slender jointed appendages projecting from beneath the carapace posterior to the antenna. A flattened specimen of the under side of the head shows the basal joints of the first five pairs of appendages (fig. 3, pl. 27) . An antenna may be traced to the second joint. The third shows only an obscure inner joint ”

“ The antennæ, which in most Crabs are extremely short, are in this species as long as the body, and each bears a double fringe of stiff hairs disposed along the upper and under sides of the antenna, but curved inwards, so that when the two antennæ are brought together parallel with each other, the hairs interlock and form a long tube. ”

“ Fam. 1. Sididae: second antennae biramous in both sexes. Sida, Straus (Fig. 11) : second antenna with three joints in the dorsal ramus, two in the ventral; the rostrum large, the teeth on the telson many. Latona, Straus: second antenna with two joints in the dorsal ramus, three in the ventral, the proximal joint of the dorsal ramus provided with a setose appendage. Daphnella, Baird: second antenna with the joints as in Latona, but with no setose appendage.
Fam. 2. Holopediidae: second antennae not biramous in the female; a rudimentary second ramus in the male. Holopedium, Zaddach. ”

“ The antennae are always conspicuous, and are very various in form; they are composed of numerous segments, and in the males of many species attain a very complex structure, especially in Bombyces and Psychidae; they doubtless function in such cases as sense-organs for the discovery of the female. ”

“ Sense Organs.—The most widely diffused sense organs are the antennae or feelers, which may serve for touch or smell, or possibly both. Each antenna is a conical or tubular outgrowth of the skin; from its apex projects a fine pencil of sense hairs borne on a protoplasmic cushion, which receives a nerve. Often the antenna is elongated, and may then contain a muscle by which it is retractile (lateral antennae of Melicerta) ; sometimes it is reduced to a slight prominence bearing the setae (dorsal antenna of this genus) . ”

“ When the eye-stalk is removed from a living lobster or prawn, it is found that under certain conditions a many-jointed appendage like the flagellum of an antennule or antenna may grow in its place. It is open to question, however, how far the evidence from such “heteromorphic regeneration” can be regarded as conclusive on the points of homology. ”

“ In my experience the antennae, are the most sensitive, and therefore the most important organs of the head—to me. In the Attacine group these stand out like delicately cut tiny fern fronds or feathers, always being broader and more prominent on the male. Other families are very similar and again they differ widely. You will find moths having pointed hair-like antennae; others heaviest at the tip in club shape, or they may be of even proportion but flat, or round, or a feathered shaft so fine as to be unnoticed as it lies pressed against the face. ”

“ That is, they propagate more energy in certain directions than in others. The ratio between the amount of energy propagated in these directions and the energy that would be propagated if the antenna were not directional is known as antenna GAIN. The gain of an antenna is constant, whether the antenna is used for transmitting or receiving. ”

“ I didn't even inspect the gleaming maze of apparatus. I merely watched him dully as he plugged in an antenna similar to the one we had left with Imee, and adjusted the things on his head.
is eyes brightened instantly. "She's still wearing her antenna," he said swiftly over his shoulder. "I'll tell her that something's happened; we must leave, but that we will return."
He sat there, frowning intently for a moment, and then dragged the antenna wearily from his head. He touched a switch somewhere, and several softly glowing bulbs turned slowly red and then dark. ”

“ For if the antennule and the basal joint of the antenna are removed, it will be seen that the base of the eye-stalk is attached, as in the crayfish, close to the middle line, on the inner side, and in front of the antennule. But it is very long and extends outwards, behind the antennule and the antenna; its corneal surface alone being visible, as it projects into the orbit
Again, the ischiopodites of the external maxillipedes are expanded into broad quadrate plates, which meet in the middle line, and close over the other manducatory organs, like two folding-doors set in a square doorway. ”

“ The fact that in certain rare cases among insects a leg may apparently be replaced by a wing tends to show that under exceptional conditions similar forms may be assumed by non-homologous parts.
The antennules (or first antennae) are almost universally regarded as true appendages, though they differ from all the other appendages in the fact that they are always innervated from the “brain” (or preoral ganglia) , and that they are uniramous in the nauplius larva and in all the Entomostracan orders. ”

“ Because the radio signal travels in the air, any obstruction (such as a mountain) between the antennas can block or reduce the signal. For an antenna 10 feet above the ground, 8 kilometers (5 miles) is the maximum line-of-sight distance. (2) The reflected wave reflects off the earth in going from the transmitting antenna to the receiving antenna. Together, the reflected wave and the direct wave are called the space wave. (3) The surface wave travels along the surface of the earth. It is the usual means of ground-wave communication. ”

“ We opened the lid, however, and I hooked the knife and the light into their proper places outside my armor. Then, with the antenna for the girl, so that we could establish connections with her, and through her, with the villagers, I moved off.
This antenna was entirely different from the one used in previous experiments. The four cross-members that clasped the head were finer, and at their junction was a flat black circular box, from which rose a black rod some six inches in height, and topped by a black sphere half the size of my fist. ”

“ In the males the first antennae are elongated and mobile (cf. Figs. 11, 19) .
Fig. 9.—Simocephalus vetulus, female. Ventral view, without the carapace; A1, A2, first and second antennae; For, head; Md, mandible; Te, telson; I-IV, first to fourth thoracic appendages.
The second antennae, the chief organs of locomotion, are biramous in all genera except Holopedium; the number of joints in each ramus, and the number of the long plumose hairs with which they are provided, are remarkably constant in whole series of genera, and are therefore useful for purposes of classification. ”

“ The effective part of the antenna is a copper wire from which the radio waves are radiated, supported on towers or poles at a height above the ground depending on the wave length used. The wire may be parallel with the earth, or vertical, or arranged at an angle, depending upon the function to be performed. ”

“ This concentration of energy provides a maximum amount of energy to be reflected off of a target, making detection of the target much more probable.
How does the parabolic reflector focus the radio waves? Radio waves behave much as light waves do. Microwaves travel in straight lines as do light rays. They may be focused or reflected, just as light rays may be. In figure 2-40, a point-radiation source is placed at the focal point F. The field leaves this antenna with a spherical wavefront. ”

“ Many expedient antennas require supports to hold the antenna above the ground. The most common supports are strong trees that can survive heavy windstorms. However, even the largest trees sway enough in the wind to break wire antennas. To keep the antenna taut and to prevent it from breaking or stretching as the trees sway, the operator attaches a spring or piece of old inner tube to one end of the antenna. If a small pulley is available, he attaches the pulley to the tree and passes a rope through the pulley. ”