Woolly apply aphid predation by the common earwig, Forficula auricularia L., and other predators was compared in high, intermediate and low earwig density plots of mature apple trees at an experimental orchard in the Netherlands. Aphid colonies were discovered and exterminated primarily by earwigs much more rapidly in the high and intermediate earwig density plots than in the low density plots. Where earwigs were excluded from trees by Tanglefoot bands around the trunks, woolly apple aphids infested 30–35% of new growth shoots whereas less than 10% of the shoots were infested where earwigs were relatively abundant. Several factors including the availability of alternate prey (e.g. Aphis pomi De Geer), earwig developmental phenology and weather probably influenced the outcome of the predation experiments. Nevertheless earwigs play an important role in suppressing woolly apple aphid populations and are potentially important, naturally occurring biological control agents for this pest. Résumé Action prédatrice du perce‐oreille (Forficula auricularia) sur le puceron lanigère, Eriosoma lanigerum L'action prédatrice exercée sur le puceron lanigère par le perceoreille commun, Forficula auricularia, et par d'autres prédateurs, a été comparée dans des parcelles d'un verger expérimental de pommiers adultes aux Pays‐Bas. Ces parcelles étaient caractérisées par des densités fortes, intermédiaires, et basses en perce‐oreilles. Les colonies de pucerons ont été découvertes et exterminées principalement par les perce‐oreilles beaucoup plus rapidement dans les parcelles à forte et moyenne densité de perce‐oreilles que dans celles à faible densité. Les pucerons lanigères ont colonisé 30 à 35% des nouvelles pousses lorsque les perce‐oreilles étaient exclus par une barrière mécanique (Tanglefoot), alors que moins de 10% des pousses ont été infestées lorsque les perce‐oreilles étaient relativement abondants. Plusieurs facteurs ont probablement influencé le résultat des expériences de prédation, notamment la présence de proies alternatives (par exemple Aphis pomi), la phénologie du développement des perce‐oreilles et le climat. Néanmoins, les perce‐oreilles ont joué un rôle important en limitant les populations du puceron lanigère, et constituent potentiellement d'importants agents de contrôle naturel de ce ravageur.

The western corn rootworm, Diabrotica virgifera virgifera Leconte (Coleoptera: Chrysomelidae), was accidentally introduced near Belgrade in Serbia just before 1992 and from there its expansion into Europe started. We have estimated its mean rate of expansion from 1992 to 2000 to be approximately 33 km year − 1 , using data from the annual surveys of the European and Mediterranean Plant Protection Organisation.We investigated whether or not D. virgifera can establish itself at certain places in Europe, taking its temperature-dependent development into account. We also estimated the time it will take D. virgifera to reach the Netherlands, considering only its dispersal by flight. All life stage transitions of D. virgifera were simulated with the program INSIM to assess whether or not it could establish itself in particular places. In the simulations, we used the available laboratory data on its life history characteristics, as well as a time series (2 -6 years) of daily minimum and maximum temperatures from weather stations across Europe. The temperature-dependent net reproduction resulting from the simulations showed that D. virgifera populations cannot establish themselves at latitudes above 55 ° N.The overall expected velocity of D. virgifera 's range expansion was computed with van den Bosch et al.'s formula [van den Bosch F, Hengeveld R & Metz JAJ (1992) Analysing the velocity of animal range expansion. Journal of Biogeography 19: 135 -150], where the expansion velocity was based on dispersal characteristics and demographic parameters. We predicted that D. virgifera will not reach the Netherlands by flight from the border of its 2000 range before 2018 using this overall expected velocity. The explanation of this late arrival is that the velocity of population expansion decreases in all directions from the centre of its 2000 range due to unfavourable temperatures.Our analysis is an improvement on former analyses in that it uses temperature-dependent life history characteristics. We stress, however, that the lack of knowledge on dispersal behaviour and on the values of life history characteristics in field situations might severely limit the applicability of the predicted velocity.

The host specific (solitary) endoparasitoid, Aphelinus mali, will parasitize all stages of woolly apple aphid but apparently prefers third stage nymphs and older hosts. Female parasitoids are generally larger than males, emerge from larger mummies and take about 1/2 day longer to complete development. The sex ratio is strongly male biased when only small hosts are available for parasitization, and strongly female biased when only large hosts are available. Pre‐adult mortality decreases with increasing mummy size suggesting higher mortality for males than females which may explain, in part, the slightly female biased sex ratio in the field. Rates of parasitism are inversely proportional to host colony size because woolly aphids in the centers of large colonies are relatively more protected from parasitoid attack than aphids on colony margins due to the dense crowding of aphids and the white, waxy secretion that covers colonies. In very small woolly aphid colonies (surface area < 37 mm2) few, if any, individuals are protected from A. mali. Rates of parasitism are greater in long, narrow colonies than in round colonies of the same size because a higher proportion of woolly aphids are located on the colony margins where parasitoids concentrate their attacks. The likelihood of successful biological control is discussed in relation to the observed patterns of parasitism. Zusammenfassung Untersuchungen zur Parasitierung von Eriosoma lanigerum Hausm. (Hom., Aphidae) durch Aphelinus mali Hal. (Hym., Aphelinidae) in bezug zum Wirtsstadium sowie zu Größe, Form und Ort der Läusekolonie Der wirtsspezifische Endoparasit Aphelinus mali parasitiert alle Entwicklungsstadien von Eriosoma lanigerum, bevorzugt aber das dritte Nymphenstadium und ältere Tiere. Weibliche Parasitoide sind generell größer als männliche, schlüpfen aus größeren Kokons und benötigen zur Entwicklung einen halben Tag länger. Das Geschlechterverhältnis ist deutlich zugunsten der Männchen verschoben, wenn nur kleine Wirtstiere zur Parasitierung zur Verfügung stehen, bzw. zugunsten der Weibchen verschoben, wenn nur große Wirte vorhanden sind. Die Mortalität der Jungtiere nimmt mit zunehmender Kokongröße ab, so daß die Mortalität bei den Männchen größer ist als bei Weibchen. Dadurch könnte erklärt werden, daß im Freiland das Geschlechterverhältnis zugunsten der Weibchen verschoben ist. Die Parasitierungsrate steht in einem umgekehrten Verhältnis zur Koloniegröße, weil die L—use im Inneren großer Kolonien besser geschützt sind als die weiter außen angesiedelten Läuse. In sehr kleinen Läusekolonien (Oberfläche < 37 mm2) können Individuen kaum vor der Parasitierung durch A. mali geschützt werden. In länglichen Kolonien ist die Parasitierungsrate höher als in rundlichen Kolonien, auch wenn sie die gleiche Läuseanzahl aufweisen. Dies ist dadurch bedingt, daß in länglichen Kolonien die Anzahl der „Randläuse” größer ist. Der Erfolg einer biologischen Bekämpfung von E. lanigerum mit A. mali wird in bezug der beobachteten Verhaltensweisen diskutiert.

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