Cerambycidae Latreille, 1802
World fauna contains 25 000 species. Source of assessment: Micheli
Lumberjack beetles, or barbel (Cerambycidae family), are much better studied than many other beetle families.
The barbel is intensely collected by amateur collectors, attracted by their beauty, forestry practitioners are involved in this family, since the barbel is a dangerous pest of the forest, the community workers also know the barbel as destroyers of wooden buildings and furniture, and theorist-biologists study the patterns of insect adaptation using the barbel theorists to live in such a special environment as wood.
In total, more than 15,000 species of these beetles are described.
This is, first of all, their slender elongated body and unusual antennae, characteristic only for this family, the length of which in many species can significantly exceed the length of the insect itself. The antennae of beetles can be thrown on their backs, but barbel never draw them under themselves - a sign that allows you to quickly distinguish them from representatives of a close family of leaf beetles. The base of the antennae is usually covered by eyes, which for this reason have a more or less kidney-shaped form. These are beetles of rather large sizes, usually their length exceeds 20 mm, but there are also very small species.
Barbel larvae have a white or yellow oblate body with a well-developed prothorax, into which the head is partially drawn. Their legs are underdeveloped, and the larvae crawl with the help of "corns" - special swellings located on the middle and posterior thorax and on most abdominal segments. Some have a spike or two small hooks at the end of their bodies to facilitate backward movement. The powerful jaws of the larvae are directed straight forward.
Barbel biology has a lot of interesting things. The active life of beetles begins with additional nutrition, which is called so because the main supply of nutrients was accumulated by the larva. A lot of longhorn beetles visit flowers at this time, eating pestles and stamens, other species feed on leaves and young bark and often gather on the juice flowing from the trees.
Having fed, the barbel leaves the flowers and fly deep into the forest or into the fields in search of plants necessary for the development of larvae. Female barbel, guided by the smell, accurately distinguish between tree species and determine their suitability for feeding larvae. Most species of longhorn beetles prefer trees that were previously weakened by attacks of other insects, but have not yet been severely destroyed by mushrooms.
The easiest way to lay eggs is on the bark, in its cracks or in the holes made in the cortex by other insects. Some species gnaw out at the same time in shallow caves, which are then smeared with special secretions. The most difficult behavior is when laying eggs in barbel of the genus Tragocephala (Tragocephala). The female begins by ringing the trunk or branch, in the wood of which the larvae will develop, gnawing the bark with their powerful jaws. The stem dries out and often breaks off in time for the moment when the larva emerging from the egg starts feeding. This barbel cannot develop in living trunks, and the female’s behavior is aimed at preparing conditions favorable for the development of larvae.
Females of each species of barbel usually lay eggs in the wood of one or more preferred tree species. However, in different geographical areas, these preferred breeds can change, and therefore, as a result, for most species of barbel, a rather wide range of forage plants is characteristic. Few species are equally willing to attach their offspring to both deciduous and coniferous species. These, however, are only those longhorn beetles whose larvae develop in highly decayed wood. By the time of their settlement, wood-destroying fungi already decompose those substances that give specificity to each tree species, and wood of different species acquires similar qualities.
The connection of barbel larvae with fungi is complex and diverse. For them, as for all tree-eating insects, the most scarce substances are proteins, of which there is an insignificant amount in wood. That is why their development lasts for several years. If we experimentally offer larvae wood artificially enriched with protein compounds, then their growth is accelerated by 10-15 times. Therefore, even in nature, barbel is looking for wood in which there would be a necessary minimum of protein compounds.
The trunk of the tree is heterogeneous: its central part consists of low-nutrient, long-dead tissues, while the outer younger layers naturally contain more nutrients. Barbel larvae distinguish these zones well, eating first in the outermost zones of the trunk. If they are transplanted into the central layers of wood during this period, they are far behind in development. But in the end, the entire thickness of dead wood becomes the prey of barbel. This is due to the fact that after some time the fungal mycelium penetrates into the central parts of the trunk. It permeates the thickness of the wood and destroys it, processing it into its pretty protein-rich hyphae. Such wood becomes more attractive to insects. Now is the time for the larvae of barbel to reap the harvest.
Many longhorn beetles entered into an even closer relationship with mushrooms. In their body, usually in the walls of the intestine or fat body, there are special organs - mycetomas, where fungi multiply, which are believed to metabolize air nitrogen and turn it into protein compounds, as well as produce some vitamins. Having such cohabitants, the larvae of these barbel can feed on clean filter paper, which, as you know, consists exclusively of cellulose. The larvae of barbel, most adapted to life in the wood, are able to absorb up to 20% of this hard-to-digest food. In their digestive juice there is a rare enzyme in the animal kingdom - cellulase, which turns sugar into one of the most stable compounds of wood - fiber. Some barbel, however, do not have strong enzymes, but then their larvae live in special conditions. So, in xystocera (Xystocera globosa), they can develop only in living wood containing at least 10% starch and sugars, i.e. compounds that are easily digestible.
The larvae of barbel are very hardy in the struggle for life when adverse nutritional conditions occur. There are cases when they lived in dried or malnutrition wood for 40–45 years and eventually turned into dwarf beetles. These observations are quite accurate, since the bugs came out of the furniture or walls of old houses, the construction date of which was precisely known. Obviously, the larvae got into the furniture or the structure of the house in the building material, but their development slowed down significantly due to adverse conditions.
Although the vast majority of the species of barbel is associated with woody vegetation, the family includes groups that have come to life in treeless steppes and deserts. They changed the thickness of the wood to the stems or roots of grasses. There are cases when close species from the same genus of barbel develop in the forest zone, and in the steppes and deserts are found in the soil at the roots of plants. However, the larvae of most species of the family live exclusively in wood, causing untold losses to forestry and those industries where various wooden structures are widely used.
The harm from wood-biting barbel is compounded by the fact that their larvae very intensively destroy wood in search of areas suitable for food. Often, wood used in food makes up only a few percent of the amount that was turned into sawdust. Strong muscles and powerful jaws of the larvae allow them to gnaw even soft metals if they block their path in contact with the wood in which the larvae gnaw. In the forest, several larvae of longhorn beetles can damage a whole tree, and in warehouses they can spoil and make logs and other wooden structures unsuitable. In wooden houses, destroying the ceilings, larvae of barrels can render the whole building unusable. Therefore, with the barbel there is a constant stubborn struggle.
In coniferous forests, barbel is particularly active as wood destroyers. Already 3-4 years after logging in cutting areas in the coniferous forest, all stumps and remains of wood are densely perforated with round holes through which adult barbel is released.
One of the first in the trunks of weakened spruces settles a black spruce barbel (Monochamus sutor), whose sizes range from 16 to 28 mm. On its shiny, black elytra there are yellow dots; the antennae of the males are noticeably longer than the body. The female lays up to 50 eggs. For each, she gnaws a cave up to 5 mm deep in the cortex. Young larvae feed first under the bark, then go deep into the woods where they winter, in spring they again move into the bark zone and continue feeding. This species is very harmful in coniferous forests, damaging spruce and to a lesser extent fir, pine and larch.
Black pine barbel (Monochamus galloprovincialis) is very similar to the previous species, but prefers pine. Adult beetles of these two species are usually found in the second half of summer; they feed on the crowns of trees, eating young twigs.
The dead bark and pine wood are preferred by the gray long-lipped lumberjack (Acanthocinus aedilis), whose males have antennae 4-5 times longer than the body. Elytra is dirty gray, pronotum with four brown spots. Its larvae develop under the bark of more than 25 different species, both deciduous and coniferous.
Mostly on spruce, pine and fir, Tetropium larvae are found, which are among the first to attack diseased trees. Their larvae can be easily distinguished by two closely connected spines located on top of the end of the body. The female brown spruce lumberjack (T.castaneum) lays eggs in bark cracks in groups of 5-6 pieces. Larvae feed on the inner layers of the cortex and grow rapidly. By autumn, in the outer layers of wood, they gnaw out a cradle where they winter, and pupate in spring. Immature larvae hibernate under the bark, and continue to feed in spring. Adult beetles appear in May - June. Their color varies from dark brown to black, legs are also black, then red, body length 10-15 mm. In the spring, you can often see females running along the bark of conifers in search of places for laying eggs.
Under strongly decayed bark of trees barbel-ragi (Rhagium) settle. These species almost do not harm. Sometimes they are even useful, since they accelerate the conversion of wood residues into organic matter of the soil. Their larvae can be distinguished by a flat brown head and an off-white color of the integument. Adult ribbed ragia beetles (R. inquisitor), living on conifers, have a somewhat unusual appearance for barbel, since their antennae are more than twice as short as their bodies. The surface of their elytra is longitudinally ribbed with light brown and grayish spots, body length up to 20 mm.