Orthoptera insects (Insecta: Orthoptera) of extreme eastern and southern arid parts of Georgia: on the example of the David Gareja Hollow and Adigeni-Aspindza ecotones

Author: Mariam Bedukadze
Keywords: Orthoptera, Hemimetabola, Gregarious phase, Solitary phase, Serotonin.
Annotation:

Insects are one of the most successful invertebrate animals. There are three main reasons of their evolutionary advancing: 1. to conquest atmosphere; 2. Cephalization (i.e. head is differentiated from other part of body) 3. Pupal stage in ontogenesis (Holometabolous). Orthoptera is distinguish from holometabolous insects. It has no pupal stage in the life cycle i.e. belongs to hemimetabola, which is an incomplete metamorphosis despite they are as successful as other ordos of insects such as: Lepidoptera, Coleoptera, Diptera, Hymenoptera they all are characterized by a complete metamorphosis. Orthopterans develop in the following stages egg, nymph and adult stages. The female grasshoppers after mating dig a hole in the soil and lay a group of the eggs in this hole, which are packed in the adhesive substance. After a few weeks of development, most species of eggs went diapause stage (hibernation) throughout autumn and winter. Eggs in the soil are less vulnerable to the abiotic and biotic factors of the environment. This is the essence of the fact that the Orthopterans did not pass on the characteristic anatomic peculiarities in the class of insects which is- Holometabolous development. “Cementing” eggs are a excellent well compensation of the pupa phase. Orthopterans as plant consumers in some cases bring the greatest harm to agrocenosis and biocenosis. The main essence of their harmfulness is made by an incredible swarm. This is one of the most selective feature of the group in their behavior ability. For example: depending the environmental conditions they change their solitary life mode and turned into large group, i.e. gregarious phase of life. Insects changes to gregarious phase are caused by hormone (serotonin). The excreted hormone is an initiation factor and as a result, as it was mentioned insect changes behavior. In the enormous swarms, there are millions of specimens of grasshoppers that are stretched hundreds of kilometers and are destroying all the green in their way. Our investigation habitats were represented in arid region of eastern and southern Georgia, particularly the driest (about 200 mm annual average rainfall) David Gareja hollow and Adigeni-Aspindza environs. It was collected 145 specimens of 3 genera and 3 species of Orthoptera. Among them Italian grasshoppers during some years turn into gregarious insects and made harm to green plants. In future, I am going to collect Orthoptera specimens, define their taxonomy and evaluate their importance, and assessment of their impact on biocenoses.