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ABSTRACT:Cockchafers are among the most dreaded insect pests in many European countries, causing economic losses in agriculture, horticulture and forestry. In forests of south-western Germany, populations of the forest cockchafer (Melolontha hippocastani) and also the field cockchafer (M. melolontha) have been increasing during the past three decades and, therefore, monitoring of these populations has been intensified. In the present field study, data on adult emergence from the soil, male swarming flights and female oogenesis, collected at three infestation sites by visual inspection, with soil eclectors and with light traps in early spring 2009-2011, are presented and discussed in the context of the current knowledge of cockchafer biology. Furthermore, three air temperature sum models for the prediction of the onset of the swarming flight period in spring, published in the early/mid 20 th century, were validated in view of their applicability in forestry practice.

Within this paper we summarize the results of the Thaumetopoea processionea monitoring at two observation sites and try to interpret population dynamics from 2006 to 2010 considering meteorological data. Furthermore, observations on the behaviour of neonates associated with oak budburst are presented and discussed. in 2007 large larval colonies occurred and population densities peaked. Massive defoliation and larval migration due to food shortage were observed regularly leading to reduced female moth fecundity. Unfavourable weather conditions probably abetted OPM population decline in spring 2008. additionally oak budburst was delayed remarkably. More detailed observations on the hatching process and the behaviour of single colonies revealed increasing mortality after two and a half weeks of starvation. the 2009 results indicated another increase of population densities, but exceeded cool and humid weather conditions in May 2010 presumably prevented a new OPM outbreak. in accordance with previous studies egg parasitisation seems to play a minor role in OPM population dynamics.

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Abstract. Thaumetopoea processionea is a serious defoliator of oak and of medical concern whose abundance has consistently increased throughout Europe during the past two decades. This study validates a previously published frost day/temperature sum model for predicting time of egg hatch of this species using five years of recent field data from South-West Germany. This model proved satisfactory for predicting the time of egg hatch of T. processionea. Hence, the model was used to retrospectively predict the time of egg hatch of T. processionea in the Karlsruhe area, which indicates that the time of egg hatch has fluctuated over the past 130 years. In the last two decades, however, predicted time of egg hatch is much earlier than the long-term average due to the increase in winter and early spring temperatures. Comparison of predicted time of egg hatch of T. processionea and long-term records of the time of foliation of its common host Quercus robur revealed that in the study area the temporal advance in the timing of both events was similar. This is not in accordance with recently published research on spring-feeding folivores, which report a diverging trend in the timing of egg hatch and budburst of their host plants as a consequence of human-induced climate change.