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

Abstract A study on orthopterologic diversity was carried out in two stations situated at 25 km (Soumaa) and 4 km (Kolea) from the Mediterranean Sea in the Mitidja plain (North Algeria) between 1991 and 1992. Mean temperatures are higher in Soumaa than in Kolea, the dry period begins earlier, at the end of spring, in Kolea. The two stations show a diversified entomofauna, as 28 species were listed in Kolea and 24 in Soumaa. Three seasonal assemblages were defined, the summer–autumn 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 Kolea, but with a longer duration of larval life. The two species that accomplish their larval life earlier in Kolea than in Soumaa 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 Kolea is discussed in the light of a possible supernumerary larval stage.