Arthropod fauna of Thymelaea hirsuta in the Egyptian western desert, with a special reference to Olpium kochi

Abstract

Abstract Background Natural and semi-natural ecosystems in the Egyptian Western Desert are in serious danger of being degraded or lost through overgrazing, and overcutting of dominant vegetation, shrubs and trees and tourism activities. The study shows the effect of Man's use during 1990 and recently in 2018 led to desertification. Results Thymelaea hirsuta (L.) (Thymelaeceae) was an important component (shrubs) in the natural ecosystems of the Egyptian Western Desert that harbors rich arthropod fauna all the year around. The spiders, pesudocorions (Arachnida: Araneae), and insects associated with this shrub were monthly sampled in 1990 at two different protected sites. One is on a very nice coastal ridge, semi-arid site, and the other is in the inland depression, arid site. The sites had distinctive characteristic of populations of non-insect predatory arthropods responding to habitat characteristics. The insects, spiders and pseudoscorpions occurred throughout the year in both sites. However, on the less arid site, the pronounced insect population occurred in winter months while the non-insect was relatively higher in summer months. On the more arid site, the highest insect population was in winter and the non-insect population was higher in autumn. The false-scorpion Olpium kochi Simon (Arachnida, Pseudoscorpionida, Olpiidae), a native rare predator to the Saharan fauna, was very common and its activity reflects its effective predatory role in both sites. In 2017–2018, several visits to the above sites showed that they were completely degraded and most of figs, olive, palm trees and dominant vegetations were removed. The survived shrub populations were very far from each other, sparse very low number and are very poor in arthropod fauna. Thus, several visits were essential to be paid just to collect enough numbers of O. kochi. The life-cycle of O. kochi is through egg-stage and three nymphal instars. There was no active feeding period by the end of each of these stages. Adults can live for 2–4 months. The developmental period takes 10 to 14 months/generation. Cannibalism tendency was among nymphs, but was very rare among fed or starved adults. Conclusions The study sites were seriously degraded with irreversible changes. The nice cost ridge was completely degraded and lost by removing the leading dominant vegetations and fruit trees and replacing building houses. Houses replaced most of the site in the inland depression for more desertification.