Effects of weak climatic variations on assemblages and life cycles of Orthoptera in North Algeria

Chantier qualité GAA study on orthopterologic diversity was carried out in two stations situated at 25 km (Soumàa) and 4 km (Koléa) from the Mediterranean Sea in the Mitidja plain (North Algeria) between 1991 and 1992. Mean temperatures are higher in Soumàa than in Koléa, the dry period begins earlier, at the end of spring, in Koléa. The two stations show a diversified entomofauna, as 28 species were listed in Koléa and 24 in Soumàa. Three seasonal assemblages were defined, the summereautumn one significantly differs between the two stations, especially for minority species. The life cycle of larvae was investigated for 6 dominant species in both stations. Four species present a precocious hatching in Koléa, but with a longer duration of larval life. The two species that accomplish their larval life earlier in Koléa than in Soumàa show the greatest lag in hatching date, suggesting an adaptation to the early onset of the dry period. The longer larval life of Ochrilidia harterti in Koléa is discussed in the light of a possible supernumerary larval stage