Scale insect

“ And there's the fire-fly, which is a soft-bodied beetle.
"And there's the very useful little beetle we call the ladybug, which is not a bug, but a beetle. The ladybug is a great help to men who own fruit orchards in the West. All over the country are to be found little bugs called scale insects. These scales are very bad for trees, because with their long, slender beaks the scales pump out the sap. ”

“ Human-in-the-loop approaches have been proposed for insect modeling [15] as have methods (limited to simple insect geometries) for inferring 3D insect shape from a single 2D image [16] . Experiments [17] , [18] with laser scanning systems like [19] have suggested that this approach has difficulties with the fine structures and the small scale of many insects, as well as reflective, transparent or iridescent surfaces.
One way to avoid these difficulties is to steer clear of 3D reconstruction altogether and simply present 2D images obtained from different viewing angles [20] . ”

“ Though gradation in size may be a sign of successive ages in certain insects, the presence of functioning wings denotes that growth has ceased; in the case of wingless insects, the characters of maturity may be less conspicuous. Although there may be at times a fairly wide range in size among fully-grown individuals of the one species, such variation is not due to age, but to certain factors influencing the insect during growth, such as the abundance or scarcity of food supply, and favourable or unfavourable climatic conditions. ”

“ With the oval pieces, it becomes another matter. What model has the Megachile when cutting her neat ellipses out of the delicate material for her wallets, the robinia-leaves? What ideal pattern guides her scissors? What system of measurement tells her the dimension? One would like to picture the insect as a living pair of compasses, capable of tracing an elliptic curve by a certain natural inflexion of its body, even as our arm traces a circle by swinging from the shoulder. A blind mechanism, the mere outcome of its organization, would alone be responsible for its geometry. ”

“ Subdivision I.—LECANODIASPIDÆ, Targioni-Tozzetti.
Female insects exhibiting in all stages the abdominal cleft and lobes. Larvæ free, naked, active. Females after the first metamorphosis constructing over themselves a carapace, shield, « 64 » or (as called herein) test, of glassy, waxy, or horny secretion. Test apparently homogeneous, really in most cases formed of aggregated segments over the insect, and prolonged beyond the body in a flat single fringe of separate, more or less triangular or quadrate, segments. Fringe not always present or conspicuous in all stages. ”

“ Insects are further characterized by having usually three distinct divisions of the body, viz.: head, thorax, and abdomen, and by undergoing certain metamorphoses or transformations. Now, while a number of other animals outside of the insect world go through similar transformations, those in the Crustacea being equally remarkable, yet, from the ease with which they are observed and the completeness of the transformations in most insects, the metamorphoses of this class have, from time immemorial, excited the greatest curiosity. ”

“ All the parts which had been forced into a constrained position, now relieved, assume that which is natural to them in the perfect insect; and the wings no longer have a questionable appearance, but become expanded into those light and exquisite structures which form the peculiar beauty and characteristic of many insects, displaying themselves almost magically in the form, it may be, of the thin, transparent membrane of the fly, or as the painted tissue of the moth or butterfly, extending frequently to five or six times their previous dimensions. ”

“ It must not be supposed that the limbs of insects are of no value in their identification. We only removed them in order to emphasize the great importance of the character derived from the regional constrictions of the body, which is considered to be certainly one of the most, if not the most, important of any. Besides this character every perfect insect should have six legs, four wings, and various appendages on the head, such as antennæ, mandibles, maxillæ, labium, etc. ”

“ When pinned the beetles are set on a corked board, the legs, &c., being placed in a natural position, and retained until dry by means of pins and pieces of paper and card. The smaller species should be mounted with transparent gum on a neat piece of card, which can be pinned in the store-box or cabinet with the others. The greatest care should be taken to set symmetrically, so that the limbs on the right-hand side of an insect are in the same position as those on the left. ”

“ After a few hours the insects should be tilted out of the bottle on to a tablecloth, and pinned exactly through the centre of the thorax. The rough surface of the tablecloth prevents them from slipping during the operation. About one-third of an inch of pin should project below the body of the insect. If a moth or butterfly dies with its wings folded upwards over the back, it must be carefully picked up between the thumb and index finger of the left hand, and the pin inserted with the corresponding fingers of the right hand. ”

“ Everyone is familiar with the main facts of such a life-story as that of a moth or butterfly. The form of the adult insect (fig. 1 a) is dominated by the wings—two pairs of scaly wings, carried respectively on the middle and hindmost of the three segments that make up the thorax or central region of the insect's body. Each of these three segments carries a pair of legs. In front of the thorax is the head on which the pair of long jointed feelers and the pair of large, sub-globular, compound eyes are the most prominent features. ”

“ In this process the entire old skin is shed, an operation well worth seeing. Under the old coat a new one has formed, which being larger, accommodates itself to the insect's increased size. The larval stage is in the case of many insects the active time when, if they are vegetable feeders, they injure crops.
When the larva has completed its growth it changes into a pupa. Some insects pass this third stage inside of silken cases they spin about themselves, others, after shedding the larval skin, find themselves each clad in a sort of horny coat of mail. We call these chrysalides. ”

“ We shall close these specimens of the industry of insects with an account of that which is displayed by the larvæ of the tineæ. The greatest part of the body of these little creatures, except the head and six fore feet, is covered over with a thin tender skin; the body of the insect is cylindrical, and lodged in a tube which is open at both ends. Soon after they are born, they begin to cover themselves, and are, therefore, seldom to be found but in these tubes or cases. They are in general so small, that it is not easy to distinguish the cases without a magnifier ”

“ Re-pinning the insect so its long axis is vertical helps with image acquisition but risks damaging the specimen, including parts, such as genitalia, that are important for the identification of some species. ”

“ Insects belong to a class of Arthropoda, and are distinguished by having the head, chest, and abdomen distinctly marked out and separable; by having not more than three pairs of legs in the adult state; by having the legs borne by the thoracic segments only; by having usually two pairs of wings; by the possession of tracheæ, or air-tubes, as respiratory organs; and by being provided with a single pair of antennæ, or feelers. The insect class is one exhibiting uniformity of type and structure. ”

“ The explanation of insect transformation is, in brief, to be found in an increasing amount of divergence between larva and imago. The most profound metamorphosis is but a special type of growth, accompanied by successive castings and renewings of the chitinous cuticle, which envelopes all arthropods. In the simplest type of insect life-story, there is no marked difference in form between the newly-hatched young and the adult, and in such cases we find that the young insect lives in the same way as the adult, has the same surroundings, eats the same food. ”

“ But the very first time that you notice the male insect flying about on a warm summer’s evening you will see why the title was given to it; for it keeps on suddenly appearing and disappearing, over and over again, just as if it had the power of making itself visible or invisible whenever it chose. The fact is that the upper surface of the wings is glossy white, while the lower is dark brown, and that as the insect flies you can see the one and not the other. So every time that the wings are lowered the moth appears; and every time that they are raised it disappears. ”

“ These take their rise from the mud at the bottom, and, extending upwards to a distance of three or four inches, afford the larva a convenient retreat from all enemies. These insects are occasionally seen swimming laboriously through the water with a peculiar zigzag motion. When out of their burrows they have considerable difficulty in keeping beneath the surface, and may be often observed floating helplessly with their exposed portions quite dry; in fact the whole integment of the insect appears to have a peculiar power of resisting the water. ”

“ When disturbed it is very sluggish, the head being immediately withdrawn into the large thoracic segment and completely concealed. The legs are very minute, and are of but little use in walking, the insect being chiefly dependent for locomotion on its large anal proleg, which is furnished with numerous horny spines. When full-grown this larva closes up one end of its burrow, and thus forms a closed cell, in which it is transformed into the pupa shown at Fig. 1a, remaining in this condition until the warmer weather calls the insect from its retreat. ”

“ Neuroptera proper (Hellgrammites, Lace-wings, Ant-lions, Caddis-flies, etc.) —Among the largest insects of this order are the Sialidæ, which includes the enormous Hellgrammite Fly, Corydalus cornutus. The larvæ of this insect are carnivorous and occur in streams, under stones, etc. The adults may be collected in neighboring situations and are also attracted to light. The Lace-wing flies (Chrysopa) , Ant-lions, etc., are carnivorous as larvæ, and occur, the former among the Aphides which infest various plants and the latter at the bottom of pits in loose, [60] sandy soil. ”

“ The difficulty, however, may be easily got over, by reversing the position of the insect, and raising the head with a needle. The antennae will attract attention by their great length. In the male insect they exceed, while in the female they fall a little short of, the total length of the body. They are well worth examination. Even a low power will show that they consist of a number of joints—usually from seventy-five to ninety. The three basal joints are much larger than the rest, and in the female the third basal is nearly as long as the first. ”

“ The male insects are, however, still more remarkable, their outward appearance readily distinguishing them from this and all other generations. When first produced, they are not of a green colour like the rest, but of a reddish brown, and have afterwards a dark line along the back; they come to their full growth in about three weeks, and then cast off their last covering, the whole insect being after this of a bright yellow colour, the wings only excepted ”

“ Cavor confirms me upon all these points. He calls them "animals," though of course they fall under no division of the classification of earthly creatures, and he points out "the insect type of anatomy had, fortunately for men, never exceeded a relatively very small size on earth." The largest terrestrial insects, living or extinct, do not as a matter of fact measure six inches in length; "but here, against the lesser gravitation of the moon, a creature certainly as much insect as vertebrate seems to have been able to attain to human and ultra-human dimensions." ”

“ Sometimes the legs seem to be reduced in number by the partial or total atrophy of one or the other pair, but in all these exceptional cases there is no difficulty in realizing that we have to deal with a true insect, because of the other characters pertaining to the class, some of which it will be well to allude to. ”

“ The price, then, of a good collection is eternal vigilance. Most insects, when exposed for any length of time to strong light, fade or lose color, and the only way to prevent such achromatism is to exclude the light.
Insect pests affecting collections include Psocidæ, Mites, Tineidæ, Coleoptera of the families Ptinidæ and Dermestidæ, these last being the most injurious. ”

“ The peculiarly leaf-like shape of the insect and its bright green colour render its discovery amongst the herbage a most difficult matter, even when its whereabouts is indicated by its cry—in fact, were it not for their music, there is little doubt that very few of these insects would ever be captured, as they are practically invisible, and are an instance of protective resemblance carried to great perfection. ”

“ For this insect has no teeth, and could not bite a blade of grass if it wanted to. And herein we see one of the peculiarities which constitute him a "bug," and which also includes in the same company our woolly swarm upon the alder twigs. In place of teeth these insects are supplied with a beak for sucking the juices of plants. If we carefully examine the dense snowy mass we find it composed of small tufts closely crowded together, each tuft being borne upon the plump body of a small insect whose beak is deeply sunk into the tender bark. ”