Biology of Hippodamia variegata Goeze (Col., Coccinellidae) and its suitability against Aphis gossypii Glov (Hom., Aphididae) on cucumber under greenhouse conditions. Research work carried out in the laboratory has shown that temperature has a great effect on the development and the amount of feeding of Hippodamia variegata. The optimum temperature for its development and voracity approaches 26°C and the threshold development temperature is about 11.22°C. Investigations on its use in cucumber greenhouses against Aphis gossypii, the release of larvae and adult forms had shown satisfactory results. The efficiency level of this ladybird is a function of the ratio predator/prey and on the level of the aphid population at the moment of the ladybird release. The effect of density of the prey on the fecundity and the settlement of this ladybird under greenhouse conditions were also studied. The biological features and the efficiency of this ladybird are discussed.

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Resume-L'etude de la dynamique des populations sur cotonnier de Aphis gossypii Glover menee a Tedla au cours de trois annees consecutives a permis de montrer l'existence de deux periodes de pullulations sur cotonnier, en juin-juillet et en septembre. La demiere pullulation, numeriquement tres importante, cause indirectement des degats economiques considerables dans le perimetre irrigue du Tadla. La pullulation de A. gossypii sur cotonnier depend principalement de la date et de l'importance des vols de contamination. L'evolution, les facteurs de developpement et de regression de ces populations sont discutes.Abstract-Studies on the population dynamics of Aphis gossypii Glover carried out on cotton in the Tadla area over a 3-year period showed two periods of rapid resurgence: June-July and September, with the highest density reached in the latter month accompanied by considerable indirect economic loss. The resurgence of Aphis gossypii populations on cotton depends mainly on the date and the density of contamination flights. The evolution and other factors responsible for the variations in the population dynamics are discussed.