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Science et changements planétaires / Sécheresse

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Sécheresse : un mal nécessaire pour les acridiens ? Volume 7, issue 2, Juin 1996

Author
Antenne Orstom, MNHN entomologie, 45 rue Buffon, 75005 Paris, France
  • Page(s) : 133-43
  • Published in: 1996

Excluding species from the tropical rain forests, whose biology is largely unknown, locusts whose ecology has been studied present an apparently contradictory relation to drought. In arid regions, they proliferate only after sufficient rain has fallen, whereas in temperate climates the triggering factor is the summer drought. Similarly, dry periods have differing effect on the long-and the short-term. Examining the expression of biotic potential and survival factors throught the lire-cycle reveals that high moisture levels are generally nefarious, while water is needed at several key biological stages: ovogenesis, oviposition, onset or embryonic development, and breaking from diapause. Environmental conditions determine several demographic responses. Geographical or even meteorological variations lead to differing biological cycles, sometimes on the intra-specific level. Most species tend to concentrate on life stages coinciding with seasons, others on number of generations and yet others still on being opportunistic. Diapause and other forms of quiescence are also adaptable, with partially delayed hatching, and diapause which may or may not be expressed, or even prolonged according to circumstance. The geographic conditions for locust’s demographic success explain the apparent contradictions in their needs and even testify to global ecological trends.