  AN ACCOUNT OF THE INSECTS NOXIOUS TO AGRICULTURE AND PLANTS IN NEW ZEALAND. THE SCALE-INSECTS By W. M. MASKELL, F.R.M.S., WELLINGTON: Mr. Maskell's Account of the Scale-Insects occurring in New Zealand is published by the State Forests and Agricultural Department, under the instructions of the Hon. John Ballance, Commissioner of State Forests. Wellington, 31st March, 1887. CONTENTS.
The number and variety of the insect pests which live on the plants of New Zealand, whether native or introduced, and the damage which they frequently do, form the excuse for the appearance of this work. The descriptions of these insects in the Transactions of the New Zealand Institute, or in works published in Europe and America, are not easily accessible to the general reader, and are also much scattered and fragmentary. It was thought therefore that the time had arrived when the information which might be useful to gardeners and tree-growers, as well as to students, might be summarized and brought together in a compendious form, and the present volume is an attempt towards this. In order to render this work complete a second volume is necessary, which should include the large number of other destructive insects preying upon various plants. For example, the "pine-blight" (Kermaphis), the "American blight" (Eriosoma), the "black leech" (Tenthredo), the cabbage caterpillar, the turnip "fly," the various aphides on roses, geraniums, &c., the grass-grub (Odontria), the codlin-moth, the borers, weevils, wireworms, and a number of others are in different places damaging trees and plants, and it would be useful to collect in one volume information regarding them. The author has had in contemplation the preparation of such a volume, and it is hoped that it may be at some future time published. Meanwhile the present is offered as, at least as far as it goes, a full description of one of the most general as well as the most noxious families of plant-parasites. The plates have been especially prepared with a double object: first, that gardeners and tree-growers might be able easily to recognize the kind of insect which might happen to be damaging their plants; and, secondly, that the student who should desire to know more of this curious family might have enough details indicated to guide him in his investigation. For the first purpose the figures have been coloured as near to nature as possible; for the second a few anatomical details have been introduced. The printing of these plates has been executed by Mr. Potts, lithographer to Mr. A. Willis, of Wanganui, and it is hoped that the reader may be well satisfied with the care and trouble which have been bestowed upon them. The author is sensible that this volume may contain numerous imperfections; but these will not, he trusts, be attributed to culpable ignorance or carelessness. EXPLANATION OF TERMS USED IN THE FOLLOWING PAGES. Abdomen. The posterior half of the body of male or female, whether joined to the anterior half or slightly separated, segmented or not. Abdominal cleft. A narrow slit in the extremity of the abdomen of LecanidinÆ and the full-grown HemicoccidinÆ only. (Plate IX., Fig. 1, b, c.) On the upper side of the body are seen the Abdominal lobes, two minute, divergent, triangular or conical, excrescences, one on each side of the cleft, in LecanidinÆ, usually bearing one or more hairs. (Plate XI., Fig. 3, b, c.) Abdominal spike. A more or less long, tubular or semi-tubular, pointed process terminating the abdomen of the male in all species, and serving as a sheath for the penis, which is a long, white, soft tube with recurved hairs. (Plate II., Fig. 3; XXI, Fig. 1, k.) Anal ring, anogenital ring. An orifice situated near the abdominal extremity of the female, either simple or compound, hairless or bearing several hairs. (Plate II., Fig. 1.) Anal tubercles. Exhibited only by the CoccidinÆ and by the larvÆ of HemicoccidinÆ: two more or less conspicuous projecting processes at the abdominal extremity of the female, without any cleft, and in most instances projecting beyond the edge; usually bearing setÆ. (Plate II., Fig. 2, c, d.) AntennÆ. Two jointed organs ("feelers") projecting from the anterior portion of the body, of variable length. (Plate I., Figs. 9, 10, 11, types.) Apodous. Without feet. Apterous. Without wings. Bucca, buccal. The mouth; belonging to the mouth. Carina, carinated. A keel or raised-ridge; keeled. Cephalic region. That part of the insect, male or female, which bears the eyes, antennÆ, and mouth, but not including the first pair of feet. Clavate. Club-shaped; somewhat knobbed. Claw. The hooked terminating joint of the foot. (Plate I., Fig. 6, cl., type.) Coxa. The first joint of the foot, springing directly from the under-side of the thoracic region. (Plate I., Figs. 6 c, 7 c.) Digitules. Appendages observed on the feet, and often useful for distinguishing species. Usually there are two pairs. The "upper pair" spring from the upper side of the extremity of the tarsus, and are generally long, fine hairs, terminating in a knob. The "lower pair" spring from the base of the claw, and are usually broader and more trumpet-shaped than the upper ones. (Plate I., Fig. 8, type.) Sometimes either pair, or both, may be absent. In Coelostoma wairoense there are no "upper" digitules, and 24 "lower" ones on the foot of the male. (Plate XXI) Dimerous. Two-jointed. Dorsum. The upper side of the body when the insect is in its natural position. Dorsal. On the upper side or dorsum. Eyes. Two coloured, granular or simple, round organs on the cephalic region of the female, near the base of the antennÆ (Plate XIV, Fig. 2, k.; Plate xx., b); two, or four, coloured, granular, simple or facetted, on the head of the male (Plate I, Figs. 14, 15; Plate XXI, Fig. 2, b). Femur. The second joint of the feet, next the coxa, joined to it by the false joint "trochanter." (Plate I, Figs. 6 f, 7 f.) Fringe. A portion of the excreted substance, cotton or wax, produced by the spinnerets on the edge of the body in certain LecanidinÆ and HemicoccidinÆ. It may be in the form of long glassy threads (Planchonia) or of more or less broad flat plates (Ctenochiton). (Plate VII, Figs. 2 d, 3 a; Plate XII, Fig. 2, a, b, c.) Haltere. A minute organ, situated just behind the wings of the males, and of which the use, either in this family or in the Diptera, has not been satisfactorily ascertained. It is often termed the "balancer." In the house-fly it has been thought to represent an organ of hearing. In Coccids it is furnished with one or more hooked bristles, and Mr. Comstock affirms that these are, probably for some purposes of flight, hooked into the posterior edges of the wings.[A] (Plate I, Fig. 17; Plate XXI, Fig. 1, m.) [A] Report of the Entomologist, U.S. Dep. of Agric. 1880, p. 277, note. Honeydew. A substance of a glutinous character produced by many species, and falling in spray from them on the leaves. (See Chap. III.) Larva. The first stage in the insect's life after emerging from the egg. Lobes, in the DiaspidinÆ, are minute, flat, more or less rounded projections, two or more, seen on the edge of the abdominal extremity, usually interspersed with spines and hairs (Plate III, Figs. 1, 3, 4, 5, l); in the LecanidinÆ, are two triangular or conical projections, usually bearing hairs, on the dorsal side of the body, one on each side of the abdominal cleft (Plate XI, Fig. 3, b, c). Mentum. A kind of secondary rostrum, or "under-lip," not altogether tubular, but rather a deepish trough, through which the rostral setÆ pass after leaving the rostrum. It may have one, two, or three joints. It is not noticeable in the DiaspidinÆ. (Plate I, Fig. 5, b.) Metamorphosis. A change of form. For the number and characters of these see Chap. II. Moniliform. Like a string of beads. Monomerous. With a single joint. Multilocular. With several divisions: a term applied to the spinneret orifices of some insects, distinguishing them from "simple" orifices, which show only a single tube. Multilocular orifices exhibit a bundle of tubes enclosed together. (Plate I, Fig. 4, c, d, p; Plate XVIII, Fig. 2, e.) Nervure. A strong vein which, starting from the attachment of the wing of the male, runs along the anterior edge of the wing, a little within it: at about half its length a branch runs obliquely towards the posterior edge. (Plate I, 16; Plate XIX, f; Plate XXI) Normal. According to rule—not exceptional. Ocelli. Two, four, or six minute circular simple organs, on the head of the male: probably organs of vision. In the MonophlebidÆ they would seem to be replaced by a smooth rounded protuberance behind the eye. (Plate i., Fig. 14, oc.; Plate VIII, Fig. 2, k, m; Plate XXI, Fig. 2, b.) Ovisac. The cottony bag or nest formed by certain species of LecanidinÆ and CoccidinÆ for the reception of their eggs. (Plate XII, Fig. 1, a, b, c; Plate XIX, a, b, c.) Peduncle, pedunculated. A stalk; stalked. Pellicle. The skin of an earlier stage, cast off at each metamorphosis; used by the DiaspidinÆ and by one genus of LecanidinÆ in the formation of the puparium or test. (Plate I, Fig. 3, a, b; Plate VII, Fig. 2, b.) Polymerous. Many-jointed. Pupa. The last stage of the male insect before emerging winged. Puparium. The shield, covering, or "scale" of the DiaspidinÆ. (Plate I, Fig. 3, e; Plates iv., v., vi.) Rostral setÆ. Three or, in a few cases, four long, fine, curling, tubular bristles springing from the rostrum, and often passing through a mentum; used for insertion into the tissues of a plant and sucking their contents. (Plate I, Fig. 5; Plate VI, only one being here shown, from the smallness of the drawings.) Rostrum. A more or less conical, tubular, projecting organ, or beak, protruding from the under-side of the cephalic region, or between the first pair of feet. It is absent in the adult female Coelostoma. It is the "mouth" of the insect. (Plate I, Fig. 5; Plate IV, Fig. 5.) Sac. The cottony, bag-like covering or nest produced by the spinnerets and concealing the insect in many of the CoccidinÆ and some LecanidinÆ. (Plate XV, Fig. 1, c; Fig. 2, b.) Scale. The shield or puparium of the DiaspidinÆ. The word is commonly used to designate the outward appearance of insects of the whole family, which are indiscriminately called "scale-insects," although many of them form no shield whatever. Secretion may be of various kinds. It is matter produced by internal organs, and expelled through the "spinnerets." In the DiaspidinÆ the secreted portion of the puparium (that is, all except the pellicles) is made up of fine, closely-woven fibres, forming the "scale." In the LecanidinÆ it probably exudes originally as fine fibres, but these become agglomerated in some cases in a waxy or horny mass, or in others are loosely collected as cotton. In the CoccidinÆ the secretion is usually cottony, or powdery like meal. Coelostoma secretes all three—wax, cotton, and meal. In some instances, as in Carteria lacca, of Africa, the wax, called "shellac," is abundant enough to be commercially valuable; or, as in the Chinese Ericerus Pe-la it can be used for making candles. Seta. A bristle—a long stiff hair. Setose. Bearing a few bristles. Spinnerets. Organs observed in various parts of the body, producing the waxy, cottony, or mealy matter. They consist of cylindrical internal tubes, sometimes ending on the skin, sometimes protruding outside it in the form of tubes, spines, or conical hairs. In the former case the orifices show them to be in some instances simple, and in others compound tubes.[B] In the DiaspidinÆ, besides being scattered over the body, the spinnerets are arranged in groups on the last abdominal segment, and these groups afford excellent characters for specific distinctions. (Plate I, Fig. 4, for types of various spinnerets; Plate III, groups of spinnerets of DiaspidinÆ.) [B] Minute anatomical details are unsuitable for this work. The student may consult Targioni-Tozzetti, "Studie sulle Cocciniglie," cap. ii., p. 26. Spiracles. "Breathing organs:" the orifices in the body of the tracheÆ or tubes conveying air to the blood. In the LecanidinÆ they are usually four; simple circles, near the edge of the body, and with a few strong spiny hairs near them. In the CoccidinÆ they are often numerous. (Plate II, Fig. 4; Plate XX, n.) Spiracular spines. Spiny hairs, usually three in number, of which one is rather long, close to the spiracles, in the LecanidinÆ. Stigma, stigmatic spines. Terms sometimes employed for spiracles, &c. Tarsus. The fourth joint of the feet, between the tibia and the claw. Its consisting of one joint (monomerous) is a distinctive character of the whole family. (Plate I, Fig. 6, ta.; Fig. 7, ta.) Test. The waxy, glassy, or horny covering produced through the spinnerets and concealing the insect in many LecanidinÆ and some CoccidinÆ. In this work it is not applied to the "scale" of DiaspidinÆ or to cottony secretions. Thoracic band. An appearance seen on the thoracic region in the male, looking like a broad transverse ribbon. Thoracic region, thorax. That part of the female or the male which bears the three pairs of feet, when the feet are present; or, if the feet are absent, the middle portion of the body, segmented or not. Tibia. The third joint of the feet, next the femur. (Plate I, Fig. 6, ti.; Fig. 7, ti.) TracheÆ. Tubes ramifying throughout the body, conveying air to the blood. Their orifices are the spiracles. The tracheÆ, as in other insects, appear as if constructed of a network of fine spiral wires. (Plate II, Fig. 4 d; Plate xx., n.) Trochanter. A small articulation, not a distinct joint (something like a knee-cap) of the feet, between the coxa and the femur. (Plate I, Fig. 6, tr.; Fig. 7, tr.) Trimerous. Three-jointed. Ventral. On the under-side, the insect being in its proper position. (COCCIDIDÆ). INTRODUCTORY. Insects are divided by naturalists into several principal orders, the distinguishing marks of which are generally very well defined—for example, the butterflies and moths belong to the order Lepidoptera, the dragon-flies to the Neuroptera, the common house-flies to the Diptera, and so on. These orders are founded upon the characters and arrangement of the wings. They are subdivided into families, and these again into genera and species. One of the orders is that of the Hemiptera, which is composed of the two following sections:—
The insects treated of in this volume are therefore placed as follows:— Class—Insecta. The genera and species will be found in their places. The common English name for this family—"scale-insects"—is not very appropriate. Some few of them have the appearance of small thin scales on leaves or twigs, but many have not. Nor are the German appellations—"gall-insekten" or "schild-lause"—more appropriate. Gardeners have given to some of them the name of "mealy-bug," which, although decidedly neither elegant nor euphonious, very fairly represents the character of that particular portion of the family. The origin of the name "CoccididÆ," or, as abbreviated often in this volume, "Coccids," is found in the old Greek word "[Greek: kokkos]," denoting a rich red dye, which was much admired by the Greeks and Romans, and which was procured from the insect now known as Kermes vermilio (the Coccus ilicis of LinnÆus). When the cochineal insect was discovered in Mexico it soon overpowered all the others, producing commercial dyes, and from it has come the title "Coccid," now applied to the whole family. Cochineal itself has of late years been pushed aside to a great extent by the aniline (coal-tar) dyes; yet it is still used for many purposes. This insect lives on the leaves of cactus. Amongst the New Zealand species described in this work will be found one, Dactylopius alpinus, which produces a red dye similar to, though probably not equal to, cochineal. Before the discovery of aniline dyes it might possibly have been worth while to cultivate this insect for its dye; but this would scarcely answer now. The CoccididÆ are, in some parts of the world, very injurious to vegetation. They seem to affect principally the warmer temperate regions. California, Florida, the Cape of Good Hope, the southern parts of Australia, Southern France and Northern Italy, and New Zealand are countries in which they are found out-of-doors in the greatest numbers. In England they are less troublesome in the open air, though in greenhouses and hothouses they abound; but, in places under glass, every gardener ought to be able to get rid of them without difficulty. For its extent New Zealand seems to furnish a larger number than any other country. The humidity of its climate and the absence of anything like severe winters in most parts of it are quite congenial to Coccids; and there is scarcely a tree in its forests or in its gardens, whether native or introduced, which is not subject to their attacks. It has not been thought necessary to include in this work a list of the books and essays written on this family of insects. The list would be a very long one; but, besides that many of the books would not be obtainable here, it would be found that very many authors have done nothing more than copy—often quite blindly and unintelligently—what others had said before them; moreover, most of them are out of date. The student or the horticulturist desiring to know more about Coccids not found in New Zealand may find full details in the reports of the Agricultural Department of the United States Government, in Dr. V. Signoret's "Essai sur les Cochenilles" (Paris), in papers by Miss Emily Smith (American naturalist, 1878-80), &c. The American Departmental Reports of Professors Riley and Comstock, Mr. Hubbard, and Mr. L. Howard contain most valuable information. English works on the subject are mostly fragmentary or inaccurate; but Mr. Douglas, of Lewisham, has lately begun to discuss the Coccids in England in a systematic manner, and probably before long others will follow suit. In India, Mr. T. W. Atkinson, of Calcutta, is studying the family. Natural science in these days tends ever more and more towards specialization, and the boundaries of scientific classes, orders, families, &c., are becoming always more and more narrowed. The student can find his time quite sufficiently occupied nowadays in the thorough investigation of so (comparatively) small a portion of the animal kingdom as is presented by the Coccids of even only one country; and the present work may not be without value to future workers in this direction. To the farmer, the gardener, the fruit-grower, and the owner of pleasure-grounds it is believed that the following chapters will also supply information at the same time correct, intelligible, and useful. CHARACTERS, LIFE-HISTORY, AND METAMORPHOSES OF THE COCCIDIDÆ. The first principal character separating the CoccididÆ from the rest of the Homoptera, and distinguishable without microscopic examination, is the absence of wings in the females at all stages of their existence. The second principal character is the absence of any apparatus for feeding and digesting in the males. From these two characters it follows that the females can only extend their operations by, at the best, crawling from plant to plant, or by being carried about by birds or other agency; also that the males cannot enjoy more than a very short existence, their work being entirely confined to impregnating the females. Hence, in any endeavours to destroy these insects, the males may be disregarded, and the females only attended to. Other distinguishing characters, chiefly microscopic, are— 1. The presence of only one joint in the tarsus or fourth joint of the leg, in both males and females (Plate I., Figs. 6 and 7, ta); 2. The presence of only a single claw terminating the leg in both males and females (Plate I., Figs. 6 and 7); 3. The presence of only two wings, with two halteres, in the full-grown males (Plate XXI.); 4. The presence of two or more eyes or ocular tubercles, in addition to the ordinary pair of eyes, in the full-grown males (Plate I., Fig. 14; Plate VIII., Fig. 1, k, m). I. The Female Insect. In general outward appearance the female insects present very variable forms. They may be either naked, or covered over with some kind of a shield, which may be fibrous, or waxy, or cottony, or they may have simply a thin powdery meal scattered over them. The covered insects are, of course, stationary, although in some cases, before reaching their full development, they move about, carrying their houses with them. The naked insects may be either stationary or active. They attach themselves either to the bark or stem of a plant or to the leaves. In the latter case it is rare to find them on the upper side; but, on turning over a leaf, the under-surface is frequently found covered thickly with them. In many cases they exude, in the form of minute globules, a whitish, thick, gummy secretion, answering probably to the "honeydew" of the AphididÆ. This secretion drops from them on to the plant, and from it grows a black fungus, which soon gives an unsightly appearance to the plant. This fungus or "smut" is an almost invariable indication that a plant is attacked by insects,[C] and may, indeed, give a useful warning to tree-growers. It is not, however, produced in appreciable quantities by all species. [C] Not necessarily a Coccid insect: the fungus may also grow on the honeydew of Aphis; but it is easy to recognize the difference between these insects. In every case there is some insect at work where the fungus is. The manner of feeding upon the plant is the same as in all the families of Homoptera—namely, by means of a protruding rostrum, beak, or trunk, situated on the under-side of the insect. As there is not, in the female CoccididÆ, any well-defined division between the head and the rest of the body, this rostrum is seen, on turning over the insect, in the form, usually, of a minute conical projection between, or nearly between, the first pair of legs, if the legs are present, or a little within the circumference, if the legs are absent (Plate I., Fig. 5). An ordinary lens will generally show, springing from the point of the conical rostrum, three or four longish, very fine, curling bristles. These bristles are, in fact, hollow tubes, and the insect, inserting them into the leaf or bark of the plant, sucks through them its food. It is thus plain that, with often great numbers of scale-insects sucking at it—pumping, as it were, its life-blood through their rostra—a plant must of necessity suffer greatly. Birds do not, as a rule, seem to care much about eating the CoccididÆ, whose work is thus little interfered with by them. The "white-eye" (Zosterops) or "blight-bird" has been seen feeding on scale-insects; but its visits are few and far between, and its assistance to the gardener in this respect not great. The CoccididÆ are, however, much subject to attacks from Hymenopterous parasites, of which some account will be found in a subsequent chapter (Chap. IV.). The effects of the CoccididÆ are not confined altogether to damage to plants: there are some species producing materials useful to man. For example, Coccus cacti produces cochineal; Carteria lacca produces shellac; Ericerus pÉ-la is used by the Chinese for candles: and others might be mentioned. But, so far, no New Zealand species appears to be of any commercial use. Dactylopius alpinus makes a rather rich red dye in alcohol; CÆlostoma zealandicum constructs thick, waxy coverings, which might possibly be turned to some account; but even these are probably not worth much. Groups. The groups into which the CoccididÆ are, in this work, divided are as follow:— 1. Female insects constructing for themselves shields composed partly of secretion, partly of the pellicles discarded from earlier stages; abdomen not cleft; legs lost at full growth. 2. Female insects naked, or covered with shields of secretion, either waxy, horny, cottony, or felted; abdomen in all stages cleft; legs either lost or retained at full growth. 3. Female insects naked, or covered with shields of waxy secretion; abdomen of larva ending in prominent processes, abdomen of adult cleft; legs either lost or retained at full growth. 4. Female insects naked, or covered with secretion either waxy, cottony, or felted; abdomen in all stages ending in prominent processes; legs either lost or retained at full growth. Life-history. The life-history of the insects in the above groups is as follows:— All of them pass through four stages of existence: 1, the egg; 2, the young larva; 3, the second stage of life, or "pupa;" 4, the adult, or full-grown insect. 1. The egg. This is, in all cases, of regularly-oval form, the colour varying from white to yellow or red (see Plate i, Fig. 1). It may be produced in great numbers, and in some cases several times in a year. As a general rule, the female ejects the eggs from her body; but there are some species, notably in the group LecanidinÆ, where the eggs are hatched within the body, the insect being thus, in a manner, viviparous. 2. The young larva (Plate I., Fig. 2). This is of precisely the same form both for the male and the female—or, rather, perhaps it should be said that no definite character has yet been discovered to show which are male and which are female larvÆ. Neglecting slight variations of form, the larva is very minute—seldom more than about 1/30 in. long, often as small as 1/100 in.—oval, flattish, possessing a rostrum and accompanying bristles (setÆ), six legs, and two antennÆ: and in all species it is fairly active, travelling as soon as hatched over the plant in search of food. 3. The second stage. Here the first distinction is noticeable between the male and the female in most cases; but this distinction usually depends not so much upon the form of the insect as upon the character of the covering it makes for itself. Confining ourselves at present to the female, there are differences now noticeable between the groups. In the DiaspidinÆ the insect begins by slipping out of the skin of the larva; but it does not cast it aside altogether: it makes use of the old skin as part of its covering. Adding to it a small portion of fibrous secretion—produced by organs called "spinnerets," which will be noticed presently—it attaches itself to the plant by its rostrum and setÆ, and lies, inert and stationary, under a little shield composed half of its old skin and half of secretion. As it also, in entering this stage, loses its legs altogether, it must remain in the position it has chosen for the rest of its life. In the LecanidinÆ and in the CoccidinÆ the skin of the larva is thrown away altogether, and the female in her second stage takes up a new position, in which she may be either naked or covered with a thin coat of secretion, active or stationary, retaining her legs in most cases, or losing them in some instances. In all the groups there is almost always some approach to the form of the full-grown insect noticeable in this second stage. 4. The full-grown insect. Here there is almost unlimited variety of form, colour, and habits. The insects may be naked or covered, active or stationary. In the DiaspidinÆ the process just described is repeated: the female slips out of her second skin, but still keeps both it and the first over her, adding more fibrous secretion from the spinnerets; so that, in fact, she lies an inert, legless, slug-like object, under a covering composed partly of the two skins, partly of secretion. (See Plate I., Fig. 3: a is the discarded larval skin, b the discarded skin of the second stage, both being used as part of the shield. In the genus Aspidiotus these skins would be in the centre instead of at one end.) In the LecanidinÆ (except in one single genus) and the CoccidinÆ the second skin is discarded altogether; but the insect may either construct a new shield or remain naked, may be either with or without legs, either active or stationary. Once this last stage of her existence entered upon, the female prepares for laying her eggs. In most species the services of a male are needed; in some, as far as can be made out after investigation of many years, no males are found. The female, if naked, either hatches her eggs in her own body or lays them on the plant; if covered, she fills her shield with the eggs. The naked insects often cover the eggs themselves—e.g., Lecanium hemisphÆricum; or, again, deposit them in an ovisac, a mass of cottony secretion—e.g., Pulvinaria camellicola or Icerya purchasi. II. The Male Insect. It has been remarked above that, as the full-grown males of the CoccididÆ are destitute of any organs for feeding whatsoever, there is no reason for making systematic attacks on them for economical purposes. Their function is simply to impregnate the females, and their life at this stage must necessarily be very brief. It will suffice in this place to observe that in all cases these males are small, two-winged flies, their size varying from about 1/40 in. to 1/4 in. in length; colour usually yellow or red; wings longer than the body, hyaline (glassy) and often iridescent, and, in repose, lying flat, partly crossing each other. The antennÆ are long, slender, and hairy, consisting of nine or ten joints. The legs are also slender and hairy, the tarsus having only one joint, and terminating in a single claw. The insects are generally very active. Types of antenna, foot, wing and haltere, and a diagram of the arrangement of the eyes and ocelli, are given in Plate I., Figs. 7, 12, 13, 14, 15, 17. The males are thus so small and rapid in their movements that it is difficult in most cases to find them in a free state. The usual way to procure them is by hatching them from the pupÆ. In their course of life they pass through four stages, as do the females—viz.: 1, the egg; 2, the larva; 3, the pupa; 4, the full-grown insect. 1. The egg is, as far as can be made out, precisely the same as that of the female, though Dr. Signoret believes that in one or two species there may perhaps be minute differences. 2. The larva is, as stated above, similar to that of the female. 3. The pupa. Here the first distinctions between the sexes may be noted, and these are principally observable in the cocoons or puparia, rather than in the insect itself—at least to outward appearance. The male pupa is, in all cases—even in those where the female pupa is naked—enclosed in some kind of covering. In the DiaspidinÆ the puparium is formed partly of fibrous secretion and partly of discarded skin; only, as the full-grown male emerges from it as a fly, and does not remain on the plant, there can be only one such skin—that of the larva; consequently it is easy to distinguish the male puparia from the shields of the adult females by the presence of only one discarded pellicle instead of two. In the LecanidinÆ and the CoccidinÆ the male puparia are distinguishable usually by a narrower and more cylindrical form than those of the females, where these latter are covered; in the naked species the males are generally in white waxy or cottony cocoons. Examination of the pupÆ in these coverings will generally show more or less developed processes on the back and sides, which are so evidently the rudiments of the future wings that the presence of a male is not doubtful. In other respects the male pupÆ are not always to be distinguished from the females. 3. The full-grown male has been described above. It is usually easy to procure specimens, provided the pupÆ are obtained. If any of these, in their coverings, are put into pillboxes with glass tops, or any place where light reaches them, they will generally produce the full-grown insect sometimes in a few days, sometimes after several weeks. The time of year for this seems very variable. Males emerge from the puparia apparently indifferently (in New Zealand) in summer or winter. PRODUCTS OF THE COCCIDIDÆ. [Waxy or cottony matter: the "honeydew" and the black fungus—"smut" or "black blight"—growing upon it.] The CoccididÆ, in some parts of the world, excrete various substances which are of commercial value, as, for example, shellac, "manna," candle-wax, &c. Cochineal is not in the same category, as it appears to be a colouring-matter pervading every cell of the tissues of the insect from which it is extracted—Coccus cacti. But there is no need to dwell here upon the ordinary excretions of the New Zealand insects, as they appear to be not sufficient either in quantity or quality for any practical service. The fibrous puparia of the DiaspidinÆ appear to be quite useless. The tests of the LecanodiaspidÆ, such as Ctenochiton perforatus, Inglisia ornata, &c., although more or less waxy (but of very brittle material, often more like glass) are much too insignificant to repay any trouble taken to collect them. Of all the family, CÆlostoma zÆlandicum, in its second stage, seems to produce the greatest amount of material, its large, hard, waxy tests being very thick and solid, and often clustered in hundreds on a root or a twig of Muhlenbeckia; but, supposing this substance (of which the true chemical nature[D] is not yet known) to be fit for some purpose, there does not seem to be any means of cultivating the insect to profit. Dactylopius alpinus produces in alcohol a rich red tint, and this not by way of excretion, but from the colouring matters of its tissues, as in the case of Coccus cacti; but here, again, the rarity of the insect and its out-of-the-way habitat would be a bar, even if nowadays it were worth while to cultivate a New Zealand cochineal. At present, therefore, there seems no reason to believe that the CoccididÆ of this country are likely to furnish any products of a useful or commercial character. | ||||||||||||||||||||||||||||||||||||||||||
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