Orussus parasitic - the natural enemy of xylophages
The Oroussids are a small relict family surviving from the Cretaceous period. Insects from the subfamily Symphyta are the only group of parasitic sitting peritoneum. In total, there are 80 species, 7 of them live in Europe. In the Palearctic zone, the parasitic orussus species lives. Insects inhabit coniferous and mixed forests. In all regions of habitat, the number of Aussie is small. They are listed in the Red Book of Russia, Ukraine, and Crimea and received protection status at the regional level.
Morphological description of the species
Orussus parasitic (Orussus abietinus) is an insect from the order Hymenoptera, a family of horntail-orussids. The length of the imago is 9-15 mm. The head, chest and first segments of the abdomen are coal-black, matte. The remaining 6 segments of the abdomen are red. The head is free, isolated. Complicated eyes are well developed. an elongated white spot above the antennae. On the forehead are three pairs of shiny tubercles. Simple eyes are arranged in a triangle. Antennae black, white spots on several segments. The mouth apparatus is gnawing.
Wings of medium length, equal in size to apex of abdomen. Venation is weak. The front pair of wings is longer than the rear, on it is visible a wide median band of brown color and a white spot along the edge. On the edge of the hind wings is a brown patch. Legs are walking, painted black. Only the knees and part of the lower leg with white spots.
Sexual dimorphism
Orussus males have 11-segmented antennae, and 10-segmented females. Females have a long and sharp ovipositor, which, when calm, is completely pulled into the abdomen.
Distribution area
The species Orussus abietinus has spread throughout the Palearctic. Insects live in North Africa, throughout Eurasia from Western Europe to the Primorsky Territory. Places of settlements are isolated, isolated from each other. In Russia, several local populations are observed, which are located in European regions, the foothills of the Caucasus, Siberia. There are finds of parasitic orussus in the Far East, in the Baikal region, the Amur Region, and Sakhalin.
Lifestyle and breeding features
Hymenoptera are insects with complete transformations. They sequentially develop from an egg to an imago, passing through the stages of larva and pupa. The adult years begin in late May and last about two weeks. Favorite habitats are mixed and coniferous forests with dead wood and fallen trees. Insects are found on the edges, thinned sections of mountain forests, fly on weakened pine trees.
The antennae of the females are located at the base of the complex eyes, next to the mouth organs. On its antennas there are contact chemoreceptors that help to find xylophagous larvae under the bark of trees. On a hot sunny day, you can see one or more females running up and down the stumps or lying trunks of trees. It is the future mothers who are looking for owners for the development of offspring. Under the bark, in the forehead there are larvae of hornails, goldfish, barbel. With a long needle-shaped ovipositor, the female pierces the bast and the layer of bark, falling into their fleshy body with a soft cover. She lays an egg in the host. The parasitic orusus larva will grow and feed on the body of the xylophagus.
Larvae are white, cylindrical in shape, with a well-developed hypognathic head capsule. Mandibles strongly sclerotized. As a result of the parasitic lifestyle inside the tunnels of tree beetles, the eyes and legs are reduced. After feeding, the larvae hibernate inside the tree. In the spring, they pupate, and by the beginning of summer, young Orusus appear, which gnaw holes and get out.
Information. Due to the secretive lifestyle, the biology of the orussus larvae is poorly understood.
Protection and limiting factors
Entomophages are found singly, their number is constantly reduced. Removing weakened and withered trees violates the natural conditions of life. Only one population with a normal number of individuals was found. The Oroussus settlement is located in the old ash forest of the Orenburg region. To increase the number of insects, it is necessary to create favorable conditions in places where the presence of individual individuals is noted. Limiting factors:
- Removal of old trees during sanitary felling, along with them the hosts for the larvae disappear.
- Deforestation of mountain forests.
- The use of chemicals against forest pests.
The useful entomophagous orussus parasitic is listed in the Red Book of Russia, it received the status of declining in number. The species was taken under protection in the Crimea, Amur, Saratov and Orenburg regions, Pribaikalsky national park.
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