SEASONAL-VARIATION IN THE ESSENTIAL OIL COMPOSITION OF COMMIPHORA-QUADRICINCTA AND ITS EFFECT ON THE MATURATION OF IMMATURE ADULTS OF THE DESERT LOCUST, SCHISTOCERCA-GREGARIA

Extracts of steam distillates of the desert shrub Commiphora quadricin cta were tested for their effects on the maturation of gregarious imma ture males and females of the desert locust, Schistocerca gregaria. Ma turation was significantly faster in immature adults exposed to the ex tract obtained before winter rains than in those exposed to the extrac t obtained after the rains, with respect to locust colour changes (yel lowing of body), mating activity, aggregation-maturation pheromone tit res (as measured by phenylacetonitrile levels in males), ovulation (as determined by the length of oocytes in females) and oviposition time. A large number of the compounds in the crude extracts were identified as terpenoids by GC-mass spectrometry. Twenty-two electrophysiologica lly active compounds were located by GC-EAD in the extract of plant sa mples taken before the rains, while extracts from plant samples taken after the rains contained 12 such active components. These results con firm a previous finding that at the onset of the rainy season, the ess ential oil of Commiphora shrubs accelerates the maturation of immature adults of the desert locust. Copyright (C) 1997 Elsevier Science Ltd.