Pine silkworm: description with photo, habitat, reproduction, damage and control methods

Pine silkworm (Dendrolimus pini)

Pest type : Pests of coniferous species Series : Lepidoptera - Lepidoptera
Family : cocoon moths - Lasiocampidae

Found everywhere. Damages Scots pine and, in rare cases, other conifers.

A butterfly with a wingspan of 60-80 mm, the color of the front wings is from yellow-brown to gray-brown, on each wing there are three transverse wavy lines and up to the middle of the wing there is a small semi-lunar white spot; when at rest, the wings are folded like a roof; the hind wings are gray, one-color. The egg is up to 2 mm in diameter, greenish at first, later dark. The last instar caterpillar is 90-100 mm long, gray-brown, with sparse reddish hairs, with dark blue spots on the dorsal side of the second and third segments; A row of rhombic spots with a light center stretches along the back. The pupa is 20-40 mm long, dark brown, in a cocoon.

Caterpillars of the third and fourth centuries overwinter in the forest floor, most often near a tree trunk; some individuals move shallowly into the soil. In the spring, at a temperature of 10 °C at the location where the caterpillars are located, they crawl along the trunks into the crown and begin to feed on young needles; they also damage May shoots and buds. They feed in the twilight and predawn hours. Over the entire development period, one caterpillar eats 20-35g of needles, 2-3g in the fall and 18-32g in the spring. Male caterpillars travel 6 centuries, female caterpillars - 7 centuries. They pupate in the first half of June among the needles on branches or on tree trunks. After 20-25 days the butterflies emerge. Their years last until mid-July.

After fertilization, females lay eggs on needles in groups of 20-150 pieces. Fertility - on average 300 eggs. After 14-20 days, the caterpillars are reborn, feeding on this year’s needles, gnawing the needles on the sides in the apical part. Caterpillars of the second instar gnaw the entire length of the needles. In October, the caterpillars move to wintering. The generation is annual.

Eating needles causes trees to weaken, branches to dry out and become infested with bark beetles and longhorned beetles.

The number of pine silkworms is reduced by more than 60 species of parasites and predators. The laid eggs are infested by egg eaters, caterpillars and pupae - braconids; ichneumonids, etc. Ants from the genus Formica and birds - cuckoo, oriole, jay - feed on caterpillars and pupae.

In wet weather, epizootics occur due to infection with fungal, bacterial and viral diseases.

Protective measures. Attracting and protecting insectivorous birds to plantings.
If the number exceeds 400-500 caterpillars per tree, treat the forest litter and butt part of the trees with biological preparations or insecticides in the early spring.

Dietary features and lifestyle

At different stages of the life cycle, nutrition and lifestyle vary. Butterflies have a very short period of existence, depending on the breed, lasting from 4-6 to 10-12 and 20-25 days. Females are inactive and do not feed. During silk production, they do not leave the cocoon and die in it. Males are more mobile than females; after fertilization, they stop their life cycle.

Caterpillars have a well-differentiated internal structure. Their digestive system consists of powerful jaws, pharynx, esophagus, crop and intestines. This allows a large amount of mulberry leaves to be absorbed. There is a circulatory and excretory system, oxygen transport is carried out by the respiratory system. The latter is of particular interest: on the sides of the body there are 9 respiratory openings (spiracles), from which branch the trachea, which are divided into small tracheoles, ending in all organs of the larva.

The caterpillars hatched from eggs are very small, the weight of one individual does not exceed 0.005 g. Their distinctive feature is appetite and non-stop feeding, rapid weight gain.

The pupal stage lasts 12-18 days. The organism inside the cocoon is immobilized, no nutrition is provided.

Dendrolimus pini

Pine moth, European pine moth, Pine moth,

Lepidoptera (Butterflies) - Lepidoptera

The pine cocoon moth is a pest of coniferous species and belongs to the group of pine-eating species of the summer-spring phenological complex. Caterpillars prefer Scots pine needles, less often than other types of conifers. Reproduction is bisexual. Development is complete. The generation is annual. Outbreaks of mass reproduction are most often observed in pine forests of the European part of Russia. Caterpillars overwinter on the forest floor. [6]

Click on photo to enlarge

Morphology

Imago . Butterfly, wingspan 60 – 80 mm. The color varies, but is most often gray-brown. On the front wings there is a wide sinuous band from gray-brown to red-brown. In addition, on each of the front wings there is a small white crescent-shaped spot.

The hind wings are monochrome. The coloring and pattern of the wings help butterflies to perfectly mimic the color of pine bark. [1]

The antennae, like all members of the family, are double-combed. [4]

Sexual dimorphism

Individuals of different sexes differ in the structure of their genitalia.

Secondary sexual characteristics:

Female . The antennal ridges are shorter than those of males. [4]

The egg is large, from 1.8 to 2.5 mm. The shape is elongated spherical. At the beginning of development they are bluish-green, later gray with a faint shine and a dark dot at the top. [6]

The larva (caterpillar) immediately after hatching is yellowish-white with transverse rows of small black warts and an orange stripe on the sides of the middle part of the abdomen.

Adult caterpillars reach a length of up to 100 mm. The color is gray with sparse reddish hairs. On the II and III segments of the chest there are dark blue, almost black spots. Along the back there is a row of diamond-shaped spots with the middle being a lighter shade. [1]

The pupa is large, 18–40 mm long. The apex of the abdomen is rounded, has a convex plate, densely covered with reddish bristles. The pupa is located in a parchment-like cocoon, 30 to 50 mm long. The color of the cocoon covers is brownish or dirty gray. Tufts of burning dark hairs are woven into it. [6]

Phenology of development (in days)

Reproduction

The butterflies' flight begins in mid-June and ends around mid-August. Already in the middle of the first month of summer, females begin laying eggs. They can be found on the bark of pine trees, branches, and pine needles. One female is capable of laying about 300 eggs, about 50 in one pile.

The development of eggs lasts from 14 to 25 days and already in early August young caterpillars appear, which, having matured, reach 8 centimeters in length. A distinctive feature of the cocoon moth at this stage is a reddish tint on the hairline and dark blue stripes on the second and third segments of the body. Thanks to this, perhaps everyone will recognize a pine silkworm in a photo, just as if they saw it in person.

Development

Imago . Butterfly flights are observed from mid-June to mid-July. [1]

Mating period . Reproduction is bisexual. Females lay fertilized eggs in groups of 20–150 pieces on needles, shoots and bark of stems. Fertility 280 – 330 pieces. [1]

Egg . At temperatures from +16°C to +18°C, the embryo develops in 16–20 days. [1]

The larva (caterpillar) , after hatching, gnaws the needles of the current year of growth, damaging the needles on the sides and in the apical part. From the second instar, the needles are gnawed along their entire length. After molting one more time around October, the caterpillars go to winter. Caterpillars of III–IV instars overwinter at a shallow depth in the forest floor, not far from the tree trunk from which they descend in the fall. In light soil they can go to a depth of 10 cm.

In spring, when the temperature of the surface layer of soil (depth up to 2 cm) rises to + 10 °C, the caterpillars awaken and climb up the trunks into the crown of fodder trees. There they begin to feed. The caterpillars of this species of cocoon moths are voracious and intensively destroy old needles. With a lack of nutrition, young needles are destroyed, buds and May shoots are gnawed off.

The caterpillars feed until mid-June. During this time they molt three to four times.

In total, during development, the number of molts reaches six, and ages - seven. [1]

The caterpillars prefer to feed on Scots pine needles. On other conifers they are found only when there is a lack of food. The species is light-loving, heat-loving, xerophilic. [2]

Doll . The caterpillar pupates on the branches and trunks of pine trees. Its development lasts 4–5 weeks. [6]

The adult emerges from the cocoon in mid-July. [1]

Features of development . The development cycle of the pine cocoon moth is one-year, but under unfavorable development conditions, the caterpillars can go to a secondary wintering and pupate only in the third summer. [1]

The outbreak of mass reproduction lasts 7–8 years. Foci of reproduction of the pine cocoon moth occur:

• in clean, dry pine forests with a fullness of average values, which are located at higher elevations;
• in green moss forests;
• in pine crops 12 – 40 years of age of varying completeness;
• on dry, poor soils, old arable lands and sands, isolated from natural pine forests. [2]

Where does the silkworm live?

Photo: Silkworm in Russia

It is believed that the birthplace of the modern silkworm is China. Already in the period 3000 BC. its mulberry groves were inhabited by a wild species of insect. Subsequently, its active domestication and spread throughout the world began. In the northern regions of China and in the south of the Primorsky Territory of Russia, wild breeds of silkworms still live today, from which, presumably, the spread of the species throughout the world began.

The habitat of the silkworm today is determined by the development of mulberry production. In order to spread it, insects were brought to many areas with a suitable climate. So, at the end of the 3rd century AD. colonies of silkworms inhabited India, and a little later moved to Europe and the Mediterranean.

For comfortable living and production of silk thread, the silkworm requires certain climatic conditions, without which the insect does not perform the main function consumed by silkworms - it does not form cocoons and does not pupate. Therefore, its habitats are areas with a warm and moderately humid climate, without sudden temperature changes, with an abundance of vegetation, and in particular, mulberry trees, the leaves of which are the main food of the silkworm.

China and India are considered the main habitat of the silkworm. They produce 60% of the world's silk. But thanks to this, sericulture has become one of the important industries in the economy of many other countries; today, silkworm colonies inhabit areas of Korea, Japan, Brazil, and in the European part they are common in certain regions of Russia, France and Italy.

Description of the insect

Appearance

The color of the pine cocoon moth varies in tone from gray-brown to brown and is similar to the color of pine bark. The upper wings of the butterfly are grayish-brown, decorated with a red-brown stripe bordered by black jagged lines. Closer to the head, there is one clearly visible small white spot on both wings. The lower wings and body have a uniform gray-brown color.

The wingspan of the female butterfly reaches 9 cm, and the male - 7 cm. In addition, the male is distinguished by the structure of the antennae, which are comb-shaped, while the female has thin thread-like antennae.

Reproduction

The most favorable places for its reproduction are dry pine forests growing at higher elevations. Butterflies begin to fly out in June and finish flying at the beginning of August.

Starting from mid-June, females lay eggs in groups of 50 on the needles, branches and bark of trees. One butterfly can lay up to 300 eggs at once. The egg stage lasts from 14 to 25 days.

In July or early August, young caterpillars emerge from the eggs and, when mature, reach 8 cm in length. The color of the caterpillars ranges from brown to ash-gray, and their hair has a reddish tint. The pine cocoon moth caterpillar can be distinguished by two dark blue velvet stripes on the second and third segments of the body.

Nutrition

The hatched caterpillars begin to feed intensively already on the second day, eating both old and young tree needles. As a rule, needles are eaten by voracious caterpillars up to

grounds. In mid-autumn, caterpillars descend from trees for the winter, hiding under moss or climbing into a litter of fallen pine needles. Some individuals climb into the ground for the winter to a depth of 10 cm.

Origin of the species and description

Photo: Silkworm

Silk production using silkworms is believed to have existed as early as the Yangshao period (around 5000 BC). Despite the fact that a huge amount of time has passed since then, the basic elements of the production process have not changed to this day. In the international classification, the silkworm is called Bombyx mori (lat.), which literally means “silk death”.

Description and features

The silkworm goes through four stages in its development. First the eggs are laid. The laying of eggs is called grena. Larvae or mulberry worms emerge from the eggs. The larvae pupate. Next, the last, most amazing phase of transformation occurs - the pupa reincarnates into a butterfly (moth, moth).

The silkworm in the photo most often appears in the form of its winged essence, that is, a moth. It is rather nondescript, painted smoky white. The wings have a standard appearance for Lepidoptera, consist of 4 segments, and spread approximately 6 cm.

The pattern on the wings is simple: a large web of longitudinal and transverse lines. The silkworm butterfly is quite furry. She has a furry body, fuzzy legs and large hairy antennae (antennae).

The silkworm has a feature associated with long-term domestication. The insect has completely lost the ability to take care of itself: butterflies are not able to fly, and voracious caterpillars do not try to find food when they are hungry.

The origin of the silkworm has not been reliably established. The domesticated form is believed to have originated from the wild silkworm. The free-living silkworm butterfly is smaller than the domesticated one. It is capable of flight, and the caterpillar independently devastates thickets of mulberry bushes.

What harm does an insect cause?

It should be remembered that each insect brings a certain benefit to green spaces. The pine cocoon moth, which can be called a forest orderly, is no exception . Its caterpillars primarily eat old needles on diseased and weakened trees.

When the population becomes too numerous, the pine cocoon moth turns into an extremely dangerous pest of pine forests.

The greatest damage to forestry is caused by cocoon moth caterpillars, which eat needles at all stages of their development and especially intensively after wintering, from early spring until

pupation. The voracious caterpillars harm not only pine forests, they can also feed on cedar, larch and spruce needles.

One adult caterpillar eats up to 60 needles per day, and during the entire period of development until pupation - about 1000 needles (approximately 36 g). This intensity of eating needles leads to the fact that damaged trees do not have time to recover and dry out completely.

In dry years, which are the most favorable for the reproduction of the pest, numerous populations of caterpillars can destroy tens of thousands of hectares of pine forests. An outbreak of mass reproduction in the same places can last about 5 years. When outbreaks occur in forestry, intensive control of the pine cocoon moth is carried out.

Silkworm - interesting facts

• The silkworm received the name “mulberry” because its caterpillars eat mulberry leaves.
• The life cycle of a silkworm: the butterfly lays eggs, the larva develops, the caterpillar, after 12 days in the cocoon the insect turns into a butterfly.
• Man has domesticated this insect, it is completely dependent on us: the caterpillar does not get its own food, the butterfly has lost the ability to fly (there is no need) and feed on its own.
• Silk thread is obtained from the cocoon of the silkworm - it is simply twisted, and the cocoon itself is used for cosmetic purposes (creams and lotions).
• One insect cocoon produces up to 1000 meters of silk thread.
• In Central and South Asia there are factories for raising silkworms and making silk thread.
• The cocoons of these caterpillars are used not only for the production of fabrics, but also in cosmetology as a means of cleansing the skin. And in Asian cuisine, the caterpillars themselves are considered a delicacy and are eaten.
• 32 layers of silk are capable of holding a pistol bullet. Therefore, silk thread is used in the production of body armor.
• The nature of a silk thread is similar to a spider's web. Silk thread is a mixture of proteins and saliva of the mulberry caterpillar, from which they make their cocoons. The thread, like the web, is very strong. For example, a silk cable will be stronger than a metal cable of the same thickness.
• At one time, in Tsarist Russia, soldiers were given silk underwear in the army, in which parasites could not live.
• In ancient times, silk was worth its weight in gold.
• Silk thread is very durable and can withstand great pressure. Silk ropes are more efficient in operation than hummocks made of steel of the same thickness.

Few people know that the gypsy moth, which is a major pest of the US forestry industry, was spread as a result of a failed experiment. As they say, I wanted the best, but what happened was the following.

At the end of the nineteenth century, one person came up with the idea to breed a new species; he planned to cross the silkworm and the gypsy moth. To get an insect that is less “picky in food”, but at the same time it must produce silk thread. For this purpose, a batch of gypsy moth cocoons was brought from Europe to America. The experiment ended in complete failure. The scientist was unable to cross these types of silkworms, but the gypsy moth has “comfortably” settled down in America and is now causing harm to the forestry of the United States of America.

How to deal with a pest

Biological methods

The pine cocoon moth has many natural enemies. Shrews and hedgehogs destroy caterpillars during the wintering period. Birds eat eggs, caterpillars, pupae and butterflies. The feathered enemies of the insect are cuckoos, tits, starlings, nuthatches, orioles, hoopoes, owls and other birds.

In addition, several species of flies, egg eaters and parasites, parasitize cocoon moth eggs, which also reduces the population size. The caterpillars also die due to a disease caused by the muscardine fungus.

Elimination of small foci of attacks by pine cocoon moths is successfully carried out using biological control methods. For this purpose, additional dispersal of entomophages is used - insects that are natural enemies of pine pests.

The most commonly used is the telenomus ovidae, which parasitizes the eggs of the pine cocoon moth and leads to their death. Telenomus is propagated in laboratory conditions on the eggs of the pest. Eggs infected with the entomophage are moved into developing foci before the butterflies begin their summer.

Telenomus spreads very well. It is capable of spreading up to 300 meters from release sites, effectively infecting fresh clutches of pine moth eggs.

Ants of the genus Formica exterminate many harmful insects, including the pine cocoon moth. They successfully deal with its young caterpillars. Ant colonies are protected and, if necessary, can be resettled in affected areas.

The goldentail is a very beautiful white butterfly, but it causes a lot of damage to gardens. Read here how to deal with this pest.

The raspberry-strawberry weevil is especially active when buds appear on strawberry bushes. Read about measures to combat this insect at https://stopvreditel.ru/rastenij/selxoz/malinno-zemlyanichnyj-dolgonosik.html link.

Chemicals

When a small population of pine cocoon moths is discovered, the infected area of ​​the forest is isolated with clearings and ditches so that the caterpillars cannot move to uninfected trees. The lower part of tree trunks in an isolated area is ringed with a trap made of caterpillar glue, which prevents caterpillars from crawling onto trees. The width of the adhesive ring is 4 cm, and the thickness is from 3 to 5 mm. 40 - 50 kg of glue is used per 1 hectare. These measures are carried out in early spring before the caterpillars emerge from hibernation.

In the event of large foci of infection, areas are pollinated with various insecticides from aircraft.

The following consumption rates are used:

1. Hexachlorane - from 0.2 to 0.3 kg per 1 ha,
2. Dust DDT (5-%) - from 15 to 20 kg per 1 ha,
3. Benzophosphate - from 1 to 3 kg per 1 ha,
4. Karbofos - from 1.2 to 4 kg per 1 ha,
5. Metaphos - from 1 to 4 kg per 1 ha.

Another control method is to apply a toxic ring 10 to 15 cm wide on tree trunks by spraying at chest level. To do this, a pesticide solution is made at the rate of 4 kg per 1 hectare of mature trees and 10 kg per 1 hectare of young trees. This procedure is carried out in early spring before the caterpillars emerge from their shelters.

Pine silkworm dendrolimus pini

The forewings are grayish-brown [2] with a wide gray transverse stripe and 3 blackish jagged lines; in the middle of the wing there is a small white spot; hind wings uniformly brown; in general, the color is very variable and generally resembles the color of pine bark [3].

The female has a span of up to 8.5 cm, the male - no more than 6 cm; It differs from the female, in addition, by thicker comb antennae and a thinner body [3].

Large caterpillars (up to 10 cm in length) are gray in color, with reddish hairs and two dark blue notches on the 2nd and 3rd thoracic rings; on the abdominal rings there are 1 or 2 dark spots with a lighter middle. The color of a caterpillar, like a butterfly, varies quite a lot and, in addition, changes with the age of the caterpillar. The caterpillar turns into a dark brown pupa lying in an elongated gray cocoon [3].

Appearance

The pine silkworm or cocoon moth is a large butterfly and caterpillar. It is a representative of the Lepidoptera order from the cocoon moth family.

The color of the insect is variable, from gray, brown to brown. In general, the color of the butterfly closely resembles pine bark. On the upper wings of all individuals there are brown-red stripes with a jagged black border. And closer to the head there is a white spot on each wing. The body and lower wings are plain.

Males are slightly smaller than females, their wingspan is 7 centimeters, females have 9. Another difference is that females have thread-like whiskers, and males have comb-like whiskers.

Notes

1. ↑ 1 2 Striganova B. R., Zakharov A. A.
   Five-language dictionary of animal names: Insects (Latin-Russian-English-German-French) / Ed. Doctor of Biology sciences, prof. B. R. Striganova. - M.: RUSSO, 2000. - P. 244. - 1060 copies. — ISBN 5-88721-162-8
2. ↑ 1 2 3 4 Pine cocoon moth
   - article from the Great Soviet Encyclopedia
3. ↑ 12345678
   Pine silkworm // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg. , 1890—1907.

Wikimedia Foundation. 2010.