Биологические науки / 7.Зоология

PhD, DSci, Psarev A., postgraduate student Еremeev Е.

The Shukshin Altai State Academy of Education, Altai region, Biysk, Russia

To the question about ecological preferences

of substrate insects

Among the various substrates populated by living organisms, there are so-called ephemeral substrates. These short-existing limited habitats with a special set of ecological qualities, isolated from other similar habitats by relatively unfavourable areas for species inhabiting them. These ephemeral substrates includes dung and carcasses of animals, fruiting bodies of fungi, substrates of holes of mammals, alluviums on the coasts of banks, etc. Such substrates formed groups of heterogeneous organisms that form the communities. These communities consist of big number of elements that differ from simple clusters by certain stability and ecological unity.

In these communities one of the main directions of evolutional process is ecological specialization which promotes the survival of species with similar ecological requirements.

This report contains the results of the study of the question of ecological relatedness of insects, in one way or another associated with separate portions of dung of animals. These results based on the field investigations on the mountain and foothill pastures of Western Siberia.

The main animals that produce dung like substrate for form of coprophilous entomocenosis on the mountain pastures of this region are horses and cows. Sheep in this respect aren’t significant.

The study of the degree of the preference by insects of dung of certain species of animals showed that there are a few groups by this criterion. The smallest attachment to a particular type of dung show predatory species. For them a concentration of food is important, but not the properties of substrate that clearly shows the examples of genera Philonthus (Staphylynidae) and Saprinus (Histeridae).

Most of the insects (210 species) are found in the dung of various animals, not just domestic. This large group can be divided into three subgroups. The first subgroup is the typical coprophilous insects that found only in the dung. The core of this group (148 species) are Coleoptera: Scarabaeidae – 54 species, Staphylinidae – 52 species, 7 species of Histeridae and 7 species of Hydrophilidae. This group includes 20 species of several families of Diptera too – Muscidae, Anthomyiidae and others, and 7 species of 4 families of Hymenoptera.

The second part of this large group (42 species) are insects that are closely linked not only with the feces of various animals but also with carrion, rotten meat – copro-necrophilous insects. These are some Coleoptera (Staphylinidae – 21 species; Histeridae – 13 species); 6 species of Diptera (Calliphoridae; Sarcophagidae) and Hymenoptera (Spalangiidae, Figitidae).

In third subgroup we include species (22) that visit dung of different animal species mainly in the last periods of its existence and at the same time are common in congeries of decaying organic matter. They are part of families Staphylinidae, Histeridae, Scarabaeidae, Hydrophylidae, Ptiliidae.

75 species of insects belong to the group that prefers cow dung and rarely found in other feces. It is taxonomically diverse group that includes 25 species of Diptera (Muscidae, Sepsidae, Scathophagidae etc.), most of the Hymenoptera – 19 species (Spalangiidae, Diapriidae, Braconidae and some others) and part of the Coleoptera – 27 species (Staphylinidae , Scarabaeidae, Hydrophilidae, Histeridae).

51 species of insects prefer horse dung. There are 8 species of Diptera (Muscidae, Anthomyiidae), 13 species of Hymenoptera (Ichneumonidae, Braconidae), 30 species of Coleoptera (Staphylinidae, Scarabaeidae, Hydrophilidae).

53 species of Diptera (with a diverse range of trophic) belong to the group that was found only on human feces: Muscidae, Sarcophagidae, Sepsidae, Faniidae.

The species that are found only in sheep dung are coprophilous Xylodromus opacus Bh. (Staphylinidae) and Phorbia sp. (Anthomyiidae). They are many times found both on separate portions of sheep dung and on the sheep's night camps.

Clear distinction between described groups is difficult to draw as evidence by experience of authors and literature data. Therefore, we believe with sufficient trustworthiness that there’s no strict ecological relatedness or specialization of one species to particular type of dung. Statements that species found only in dung such cow dung, in our opinion, are not quite correct. We can say only about preference to certain type of dung when there are feces of several species of animals, the insects choose one of them. This preference is expressed in early hours of the existence of the feces and more clearly manifested in the group of coprophagous insects when between its different types there are structural differences. But often even the species of this trophic group in the absence or lack of necessary substrate, that happens when the species composition of grazing animals changes on pastures or decrease its number, use any available at this time.

Comparative analysis (with usage of Jacard similarity coefficient) of the groups of coprophilous insects in horse and cow dung shows a very high part of coincidence of species composition (0,71) which indirectly confirms that we said before.

Thus, the study of the question of relatedness of coprophilous insects showed that they have no narrow ecological specialization. We can say only about preference of certain type of dung when there are feces of several species of animals, the insects choose one of them. In the absence of preferred type of dung coprobionts use any available at this time.