This study compared oviposition by Hehothis armigera (Hubner) and H. punctigera (Wallengren) on four cotton cultivars: a smooth-leaf cultivar ('Deltapine Smooth Leaf') and a genetically similar hirsute cultivar ('Deltapine 16'), an okra leaf cultivar ('Coker 201 Okra Leaf') and a near-isogenic normal-leaf cultivar ('Coker 201 Normal Leaf'). In the glasshouse, 'Deltapine Smooth Leaf' plants received the lowest number of eggs and 'Coker 201 Normal Leaf' the highest. In the field, 'Deltapine Smooth Leaf' had the fewest eggs and 'Coker 201 Okra Leaf' the most. Both Heliothis species exhibited similar oviposition on different structures on each cultivar for each plant growth stage. Most eggs were laid on mature leaves. In the glasshouse, the lower leaf surface received more eggs than the upper; the upper surface received more eggs in the field. Terminal buds received the fewest eggs in the glasshouse, but in the field, egg numbers on terminal buds, bracts, stems, petioles, and stipules were similar. Analysis of the relative effect of the okra leaf and smooth-leaf traits on oviposition indicates higher oviposition on the okra leaf than on the smooth-leaf plants, although trichome density might in part be responsible for some of the differences.

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Immature Chrysopa sp. and Nabis capsiformis required 335 and 325 d°, respectively, for development from egg to adult, while larvae of Micromus tasmaniae were able to complete development at 5°. Mean adult female longevity and oviposition rate at 23° were 52 d (max. 83 d) and 18.1 eggs/d, and 30 d (max. 43 d) and 10.4 eggs/d for C. sp. and N. capsiformis respectively, and oviposition rate of M. tasmaniae averaged 19.1 eggs/d during 5 weeks. Reduced longevity and increased oviposition rate at higher temperatures were accounted for by basing adult biology on physiological time above the immature developmental thresholds. Intrinsic rates of increase were thus calculated as 9.820, 6.868, and 8.366 ♀ eggs/103 d° above thresholds of 10.5°, −2.9°, and 11.3° for C. sp., M. tasmaniae, and N. capsiformis, respectively. RÉSUMÉ INFLUENCE DE LA TEMPERATURE SUR LA BIOLOGIE DE CHRYSOPA SP., MICROMUS TASMANIAE ET NABIS CAPSIFORMIS L'examen a porté sur l'influence de différentes températures constantes sur le développement et la biologie imaginale de trois espèces prédatrices (Chrysopa sp., peut‐être C. signata, Micromus tasmaniae et Nabis capsiformis) récoltées dans des champs de coton du sud‐est du Queensland en Australie. C. sp. et N. capsiformis ont besoin respectivement de 335° au dessus d'un seuil de 10.5° et de 325° au dessus d'un seuil del 1.3°, pour se développer de l'oeuf à l'adulte. Les larves de M. tasmaniae pouvant effectuer la totalité de leur dévelopment a 5°. A 23° les longévités des femelles adultes et les taux de ponte de C. sp. et N. capsiformis sout en moyenne de 52 j. (maximum 83) et 30 j. (maximum 43) d'une part et 18.1 et 10.4 œufs par jour d'autre part. Le taux de ponte de M. tasmaniae est de 19,1 œufs par jour pendant 5 semaines à 23°. La longévité réduite et le taux de ponte accru aux températures supérieures sont interprétés en basant la biologie imaginale sur le temps physiologique au dessus des seuils de développement. Les taux d'accroissement intrinsèque (rm) sont plus élevés aux températures élevées, principalement à la suite du taux de développement accru. M. tasmaniae possède le rm le plus élevé à toutes les températures par suite d'un développement rapide et de seuils thermiques bas, d'une brève période précédant la ponte et d'une date de ponte maximum précoce. Le rm de C. sp. est plus élevé que celui de N. capsiformis à la suite de son taux de ponte plus élevé. Les valeurs de rm fixées à partir du temps physiologique sont respectivement: 9,820, 6.868 et 8,366 œufs femelles/103 d° au dessus des seuils de 10,5°, −2,9° et 11,3° pour C. sp., M. tasmaniae et N. capsiformis.

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The nectariless, near-isogenic cultivar of 'Stoneville 7A' produced a higher yield than its nectaried counterpart due to: (I) an intrinsically greater yield potential. and (2) a reduced attractiveness to insect pests which resulted in a reduction in pest damage. The greatest yield advantage occurred with the unsprayed field comparison where the nectariless cultivar had ca. 40% less damaged fruit over each of the 4 years. The nectariless cultivar also matured earlier, as much as 18 days with the unsprayed field comparison. The reduction in pest damage and earlier maturity for the nectariless cultivar has considerable significance for cotton crop production.