Study of the predatory action of some Carabidae against some Aphididae in the region of Ouargla

Abstract

This work aimed to carry out an inventory of the coleopterofauna in some agricultural envirnments of the region of Ourgla, to study some bioecological traits, the bioecology and the spatiotemporal variations of a coleopteran predator family, the Carabidae, and to testify the role of some carabids in aphids’ biocontrol. The study sites (three palm groves with different maintening conditions, a wheat and an alflfa culture) were densely vegetated, presenting 11 botanical families, and characterized with sandy- loam soils, low levels of soil moisture and organic matter and pH values varying between 8.5 and 8.75. Their Arthropodologoical species belonged to 4 classes and 16 orders between which Hymenoptera, Heteroptera and Coleoptera dominated. Coleoptera inventory showed that palm groves were the most diversified while alfalfa culture terrain were the less diversified. Among the families, Carabidae, Tenebrionidae and Coccinellidae were the most diversified. However Cybocephalidae, Coccinellidae, Carabidae and Tenebrionidae families were the most abundante. In termes of species abundances, Cybocephalus seminulum, Pharoscimnus numidicus and Pharoscimnus ovoideus were the most dominante in the palm groves, while Lophyra flaxuosa dominated in the two other sites. These beetles belong to 7 diet categories clearly dominated with predatory species. Of the 117 Coleopteran species inventoried in the study sites, 28 species were carabids. They belonged to thirteen sub-families among which Harpalinae was the most diversified, Lebiinae came in second, followed by Scaritinae then Carabinae. In terms of abundance, the Cicindelinae sub-family predominated. The Harpalinae subfamily ranked second, than the Lebiinae and Scaritinae. Among Carabidae genera, Harpalus and Scarites were the most diversified while Lophyra and Cicindela were the most dominant. Coming to carabids sptial distribution, diversity and abundances were at their maximun in the first three sites. The Shannon-Weaver index H' in the five sites varied between a minimum of 0.98 bits (site 5) and a maximum of 1.25 bits (site 4), while the values of H'max varied between 3 bits and 3.49 bits. The very similar values of the equitability index at almost all sampling levels (0.25 and 0.42) testified to a high degree of irregularity in the Carabidae population. The Sempson index results, which tend remarkably towards 0, were better able to show the great dominance of one or more species over the others. Hill's values, which were very close and tended towards 0 in the sites 1, 2 and 3, confirmed a higher level of diversity in terms of species richness than in terms of number of individuals. The IndVal analysis revealed the presence of only one species characteristic of the the region of Ouargla in all the study sites (Lophyra flexuosa). Most of the specimens were captured between Spring and Summer. Concernind aphids inventory, Aphis craccivora was the most abundant species then came A. fabae, A. gossypii and M. percicae respectively, with a maximum of catches recorded on March. The results obtained from the efficacity of some carabid species on aphids biocontrol tests have shown three main points: the number of aphids and the cumulative temperature are closely related, the population density of the predators is one of the factors determining their predation efficiency, the efficacity increases from the big sized species to the small sized ones.As for perspectives, we have to make more efforts to betterstudy the diversity and spatiotemporal distribution of ground beetles in arid ecosystems. That will allow us to identify and locate endemic, rare, or endangered species for conservation. In the future, pest management, particularly aphid control, should take carabids into consideration.