Distribution et limites écologiques du criquet nomade Nomadacris septemfasciata (Serville, 1838) à Madagascar

Abstract

The red locust Nomadacris septemfasciata (Serville,1838) has been studied for a long time in Southern Africa where its outbreak areas are known and regularly assessed. This locust is also observed in Madagascar, but only recently have gregarious individuals been observed and described: in 1997 in the south and in 2002 in the north part of the island. This locust has only one generation per year, with a long immature adult period throughout the dry season. In this work, by means of all data recorded since 1907, a first chorology study of Nomadacris septemfasciata is set up at the national level. Archival data were improved with data collected during rural investigations and field surveys. Chorology data were analyzed with physical and weather ecological parameters (altitude, rainfall and temperature).Altogether, 717 measures were collected. By contrast with the migratory locust, another pest in Madagascar, the distribution and ecological requirements of the red locust do not seem to correlate only with altitude, rainfall and temperature: its response to the micro-environment also plays a prominent role.The red locust ranges between 0 and 2000 m elevation. An area of diapause can be delimited on the edge of the highlands and the east coast. The breeding area is wider and more extensive, from middle areas to the whole of the western slope, from south to north. It is in the Sofia area (in the northwest of the island) that most of the populations (hopper bands and swarms) were observed between 1999 and 2003.