Summary 1.Harmonia axyridis is a generalist predator with a high range of accepted prey. Prey differ in nutritive contents, energetic values and cost associated with their capture and ingestion. As a result of selection pressures, animals will tend to hunt for their prey efficiently. In this paper we evaluated the suitability of Myzus persicae and Aphis fabae to the adults of the aulica phenotype of H. axyridis , their feeding preferences and the impact of mixed diets on their fitness. Feeding preference of predators was evaluated through their response to different relative abundance of prey. 2. Under a single diet regime, the adults of the aulica phenotype fed on more individuals M. persicae than A. fabae but consumed less biomass from the former. None of those prey affect relative growth rate and reproductive capacity of the ladybeetles. 3. Males and females present different types of response to three levels of different relative abundance of prey. While males show a constant feeding preference for M. persicae , females did not show a feeding preference (i.e. null switching response). Under a mixed diet regime, adults' voracity gradually increased as the proportion of M. persicae increased, but biomass consumed and relative growth rate was not affected. On the other hand, fecundity and fertility increased. 4. Our results suggest that H. axyridis present self-selection behaviour because they agree with the basic criteria of Waldbauer and Friedman's self-selection, i.e. (i) the animal's choice of food or nutrients is non-random, and (ii) the coccinellid benefits from self-selecting.

Abstract. I assessed effects of the widest range of temperatures ever examined on maximal food-chain length (L) and macroinvertebrate species richness (S) by a worldwide comparison of spring ecosystems with mean water temperatures (T) ranging from 4.5 to 93uC. Eukaryotic L averaged ,3.2 and varied independently of T between 4.5 and 31uC. However, over the relatively narrow T range of 35 to 50uC, L dropped abruptly to 0 and remained so up to 91uC. The negatively nonlinear relationships of L vs T and macroinvertebrate S vs T both deviated from predictions based upon metabolic theory, and the negative effect of T on S contrasted with positive relationships observed at larger regional scales. Thermal tolerance limits apparently play a major role in causing these relationships, but other factors also may be involved (e.g., availability of colonists adapted to different temperatures and temperature-dependent rates of resource use and species interactions that affect population establishment and persistence).

Abstract.The coccinellid H. axyridis shows considerable intraspecific variability of elytral patterns. In this paper, we suggest that a genotype that confers a specific pattern of elytra could also confer other specific autecological attributes. The aim of this paper is to compare fitness parameters of two phenotypes (aulica and nigra). Aulica is a common morph characterized by two light red areas that nearly cover the whole elytra, leaving a narrow black border, whereas nigra is completely black; the latter is a rare morph that was naturally obtained from mass cultures. Intraspecific differences occur between H. axyridis phenotypes. The aulica phenotype is more voracious than nigra. Consumption rate of males is higher in aulica than in nigra, but there is no difference for females. Larval biomass of aulica is generally higher than that of nigra. The maximum body-weights reached by larval instars and adults are signifi cantly higher for aulica. Aulica also has greater longevity and reproductive capacity. Only life stage duration of eggs and pre-pupae differ between the two phenotypes. Nigra shows lower fecundity and fertility. Our study showed that the strong differences in phenotype traits of the coccinellid H. axyridis could affect its fitness.

R~sum~Les coccinelles aphidiphages Harmonia axyridis Pallas et Semiadalia undecimnotata Schneider (Coccinellidae) ont 6t6 61ev6es pendant trois g6n6rations ~t raide d'oeufs d'Anagasta kuehnieila Zell. (Pyralidae) tu6s par une exposition hun rayonnement ultraviolet. Chez la premiere esp6ce, cette proie de substitution pr6sente une valeur alimentaire comparable sice nest pas sup6rieure ~ celle du puceron Acyrthosiphonpisum (Harris). Ces r6sultats permettent d'envisager, d~s ~t pr6sent, une production massive dans ces conditions trophiques. La mise en place d'un 61evage continu d6pend de l'6volution sur un grand nombre de g6n6rations de certains param~tres biologiques notamment de la fertilit6 des femelles. Chez la seconde esp~ce, une telle application para~t impossible pour l'instant.

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