Part 13

Beetles (Fig. 65) are insects with biting mouth-parts, and strongly developed prothorax united with the mesothorax so as to permit free movement. The fore wings are in the form of hard covers, leaving exposed only the head, neck-shield (i.e. the dorsal side of the prothorax), a three-cornered bit of the mesothorax (scutellum), and sometimes the tip of the abdomen. Flight is effected by the hind wings alone, which in a state of rest are drawn back under the wing-covers. The metamorphosis is complete; the larvæ are legless, or with thoracic legs only, and have a hard head with biting mouth-parts; change into free pupæ (p. 93).

Family: =Carabidæ= (Ground Beetles).

Usually elongated, slender; with long slender legs, five-jointed tarsi, eleven-jointed antennæ, powerful jaws (Figs. 68, 69). Run rapidly; usually keep on the ground; hide themselves during the day, but are very active at night; with very few exceptions feed entirely on other insects; when touched squirt an acrid stinking fluid out of the abdomen. Larvæ longish, six-legged, with short antennæ and sharp jaws, with a few exceptions live exclusively on other insects and lower animals.

Several species are of service, both in the adult and larval conditions, since they destroy injurious insects, e.g. surface caterpillars, wireworms, cockchafers, grubs, crane-fly larvæ. The following do good in cultivated fields: =Golden Ground Beetle= (Carabus auratus), =Garden Ground Beetle= (C. hortensis), =Granulated Ground Beetle= (C. granulatus), =Cross-barred Ground Beetle= (C. cancellatus), =Field Ground Beetle= (C. nemoralis), =Large-headed Ground Beetle= (Cephalotes vulgaris), species of Harpalus, Pterostichus, etc.

FIG. 68.—A Ground Beetle (Carabus auronitens). ]

FIG. 69.—Corn Ground Beetle (Zabrus gibbus) and larva. ]

The only destructive form is the =Corn Ground Beetle= (Zabrus gibbus, Fig. 69); short, thick-set; back black; belly, legs, and antennæ dark brown. Larva cylindrical, slightly hairy, brown, with yellowish white belly; head broad and flattened, black. The beetles (June, July) usually remain hidden in the soil during the day, climbing up the stalks of barley, wheat, and rye during the evening and in dull weather, and eating the grain in the ear. The larvæ remain during the day in vertical holes which they dig out; but at night and during dull weather they devour the overground parts of the grain-plants mentioned above, especially the hearts of young plants. They are destructive both in autumn and spring, damaging winter and summer grain. The larval condition is maintained for three years, the animal then turning into a pupa during July. Its ravages are limited to special years. Remedy: Sowing oats, peas, or vetches, or planting potatoes in fields infested by the beetles or their larvæ; collecting the beetles in the evening when they are in the ears.

Family: =Staphylinidæ= (Rove Beetles).

FIG. 70.—Rove Beetle (Staphylinus erythropterus). ]

FIG. 71.—The Black Burying Beetle (Silpha atrata) and larva. ]

Usually elongated, small (Fig. 70). The short truncated wing-covers leave the whole of the abdomen exposed. The rove beetles resemble the earwigs in their appearance and in a way they have of frequently lifting up the hinder end of the body and turning it forwards. Tarsi five-jointed, jaws strongly developed. The six-legged larvæ resemble those of the ground beetles, but have a relatively large head. The beetles live through the winter; the metamorphosis takes place in autumn. Live on the ground under fallen leaves, also under the bark of trees; in carcases. Some chiefly eat insects living in the soil and noxious insects; others, dung and decomposing matter. (Species of Staphylinus, and of Ocypus, e.g. O. olens, the =Devil’s Coach Horse=.) Several are of service. A few devour the parts of plants. Anthobium torquatum is found in large numbers in the flowers of rape, devouring the petals, stamens, and pollen.

Family: =Silphidæ= (Burying, or Sexton Beetles).

The antennæ either thicken gradually or have only the end-joints larger; body flat; head projecting; tarsi five-jointed. The burying beetles and their larvæ feed on dead animals. A few (sp. of Necrophorus) bury the whole animal in the earth, and lay their eggs in it. Failing carrion, some of them can live on vegetable food; these sometimes do harm. Others prefer living insects and snails. They are of service in the economy of nature by doing away with stinking bodies. The following are sometimes harmful: =Black Burying Beetle= (Silpha atrata, Fig. 71), the larvæ of which often do much damage in fields of beetroot; Silpha opaca (=Beet Carrion Beetle=), and S. reticulata, which, in the adult condition, may do harm to several kinds of plants. Remedies need not be considered, as it is only rarely they increase so largely as to make the supply of carrion insufficient, and consequently attack plants.

Family: =Nitidulidæ= (Shine Beetles).

Small. Antennæ club-shaped, eleven-jointed. Tarsi five-jointed. A few species live on carrion and on fungi, others under the bark of trees, a few in flowers. To these last belongs the =Turnip Flower Beetle= (Meligethes æneus); somewhat convex, elongated oval; shining metallic greenish black, finely dotted. Occurs in the inflorescences of turnip, rape, and allied species; also in the flowers of mustard, charlock, and similar crucifers, and species of buttercup (Ranunculus). At the beginning of spring, the turnip-flower beetle bores into the buds of turnip, rape, etc., and, later on, attacks the flowers. It perforates the petals, devours the stamens and pollen, and, lastly, the pistil. The infested flowers wither. Three to four beetles are often found in a single flower. The female soon lays her eggs, separately, in the ovary of the flower. One to two weeks later the larvæ may be found in the flowers, one or more in each. The larvæ, one-fiftieth of an inch long to begin with, are, when ready to become pupæ, about one-fifth of an inch long, cylindrical, yellowish white with blackish brown head; they have three pairs of short thoracic legs, as well as a pair of caudal pro-legs. Each segment of the body has two dark blotches on its upper side. On an average, the larvæ reach their full size in four to five weeks. They are first found at the bottom of the flower, where they gnaw the stamens and ovary. They then wander from flower to flower, until ready to become pupæ. If there are no more flowers in the neighbourhood they attack the developing pods, first gnaw the green husk, then bore through it and devour the young seeds. Become pupæ in the soil. The beetle emerges after a fourteen days’ pupa rest. At least two, usually three, sometimes four generations. Remedy: Rooting out charlock and the species of buttercup. Selection of strongly growing varieties of turnip, rape, etc., which blossom late (and therefore soon finish blooming). Drill-culture.

Family: =Cryptophagidæ= (Secret-eating Beetles).

Very minute. Antennæ composed of eleven joints, of which the three last form a club. Legs wide apart; tarsi five-jointed. Live in flowers, fungi, dead parts of plants, under bark, in the earth, in humblebees’ and ants’ nests, etc. The =Beet Beetle= (Atomaria linearis) is harmful: longish, egg-shaped, strongly convex; neck-shield as long as broad. Brownish black or dark brown. In fields where beet is cultivated for several years in succession, the beetles often increase in a prodigious way. They attack the seedlings, and devour the base of the stalk just below the surface of the soil, sometimes biting it half through. The attacked seedlings often die even before the cotyledons appear above the surface of the soil. Looking, therefore, in spring at fields infested by the beet beetle, the seedlings will appear quite normally developed in some few places, while in some other places there may be no plants at all: in many spots, again, small plants will be seen bearing only seed-leaves, withered and yellow. These cannot be pulled out of the ground, for they break off at the place gnawed by the beetle. It is often necessary to give two or three successive sowings, as the young crop is attacked again and again. The larva of the beet beetle is still unknown, though this undoubtedly develops in the beet-fields. Remedy: Suitable rotation. When the conditions will not permit this, the seed must be sown thickly, so that as many seedlings as possible may remain sound, should the beetles exert their destructive influence in the spring.

Family: =Lamellicornia= (Chafers).

FIG. 72.—a, Antennæ of male; b, of female Cockchafer. ]

Body strong, stout (Fig. 65). The first joints of the antennæ have the usual shape; the last, three to seven, are very short, but broadened out on the inner side into leaf-like appendages, so that the end of the antennæ is fan-shaped (Fig. 72). The little leaves are laid together when at rest, so as to form a club-shaped thickened end; in flight, and when the attention of the beetle is excited, they are spread out like a fan. Legs strong; feet five-jointed. Flight rapid, somewhat awkward. Larvæ thick; body cylindrical, but curved; head hard, brown; rest of the body thin-skinned and yellowish white. The first three segments of the body bear legs. The curved larvæ can move about in the soil, but not on the surface. The beetles and larvæ devour vegetable substances; a comparatively small number of species feed on dung.

FIG. 73.—a, abdomen of Common; b, of Horse-chestnut Cockchafer. ]

The =Common Cockchafer= (Melolontha vulgaris) will serve as a type of the lamellicorns (Fig. 65). The last segment of the body forms a gradually tapering process. The club of the antennæ with seven large leaflets in the male, and six smaller leaflets in the female (Fig. 72). Head, neck-shield, entire ventral surface, and legs, black; although these parts, with the exception of the head, may be reddish brown. Many specimens are thickly clothed with numerous white hairs; others are almost hairless. The beetles usually appear during May, but sometimes by mid April, and sometimes not till the beginning of June. In the evening they leave the soil and seek the neighbouring trees. They devour the leaves and especially the buds of oak, horse-chestnut, beech, poplar, willow, cherry, and other forest and fruit trees, but spare the lime and generally the morel cherry. Of coniferous trees it only devours the needles of larch and the young shoots of pine. Among cabbage-like plants it only devours rape. In “chafer years” the cockchafer becomes a veritable scourge to the farmer. For the purpose of laying her eggs (about forty in number), the female selects by preference a fertile soil rich in humus, but will also put up with a dry sandy soil. The grubs devour the grass and clover-roots in meadows, and, in cultivated fields, the roots of grain-plants, peas, and beans, rape, cabbage, etc., also turnips and potatoes; in gardens the roots of many vegetables and flowers, and, in particular, the underground parts of strawberry plants. If, on poor sandy soil, they can get nothing else, they devour the bark of oak and fir. Cockchafers take three to four years for their development: four in England, North Germany, and Central Germany; three in South France, Switzerland, the Rhine district, and Holland. In regions where the insect is abundant, every third or fourth year is a “chaferyear,” when the beetles appear in millions, while scarcely a cockchafer can be found in the intervening years. In districts less infested there is not the same marked distinction. It therefore appears that cockchafers and their larvæ are to be reckoned as injurious insects: their occurrence, however, is local. Natural enemies: moles, shrews, bats, foxes, crow-like birds, starlings, sparrows, owls, and the large species of ground-beetle. Winter floods do no harm to the grubs, which are then deep in the ground,—but this is not the case with floods occurring in summer, when they are near the surface eating the roots of the plants. Remedies: Collecting the grubs turned up during ploughing. Catching the cockchafers; this is very expensive, since it has to be done very energetically if most of them have left the pupastage. A part of the expense may, however, be recouped by using the cockchafers as manure.

The =Horse-chestnut Cockchafer= (Melolontha hippocastani) has a short slender caudal process, somewhat broader at the tip (Fig. 73). Its habits are in no way different from those of the preceding species.

The =Buckwheat Beetle= (Phyllopertha horticola), one-third to one-fifth of an inch long, without a caudal process. Shining blackish green, with yellowish brown elytra. Dark-coloured specimens are also found. The beetles appear in June; in some years they occur, like cockchafers, in large numbers. Habits of the beetle and of the small grub not markedly different from those of the cockchafer.

The =Rye Chafer= (Anisoplia fruticola), somewhat larger than the buckwheat beetle, in other respects very like it, but with a snout-like projection of the thickened skin of the head. Dark bronzy green, whitish on the under side. Wing-covers yellowish brown. On poor sandy soil, on the flowering ears of rye. The beetles gnaw the flowers.

Family: =Elateridæ= (Click Beetles).

FIG. 74.—The Skipjack (Agriotes lineatus): 1, magnified larva, below it the under side of the tip of the abdomen and the larva, natural size; 2, the beetle; 3, under side of the head of the larva, strongly magnified. a, maxilla; b, lower lip; d, labial palp; e, k, inner and outer maxillary palps; f, antennæ. ]

The Click Beetles (Fig. 74) are longish, of equal breadth all along, tolerably blunt at the hind end. Neck-shield strongly developed. Antennæ “serrated,” i.e. made up of three-cornered joints. Feet five-jointed. Looking at the under side a spine may be seen on the hinder margin of the prothorax (Fig. 75, b), and on the mesothorax (c) a furrow which receives the spine when the body is extended, but the spine is drawn out of it if the prothorax and mesothorax are lifted up from anything they happen to rest on (Fig. 75). A skipjack that has fallen upon its back first draws its antennæ and legs close to its body, and then bends this in such a way that the head and prothorax make an angle with the rest of the thorax and the abdomen. In this way the junction of the prothorax and mesothorax is lifted up, and the spine drawn as far as possible out of the furrow. As soon as the beetle has taken up this attitude, it can spring back into its usual position by lifting the two ends of the body and pressing the spine forcibly back into the furrow, whereby it is jerked against the ground with such a shock that its elasticity makes it spring into the air, where it turns round and comes down again ventral side below. The larvæ (“wireworms,” Fig. 74, 1) are like meal-worms, elongated, always flattened on the ventral side, and sometimes on the dorsal side as well. The head is dark brown, the twelve remaining segments of the body yellow to yellowish brown; the first three segments of the body bear three pairs of very small legs; the last segment has a pair of caudal pro-legs.