Adults of some coccinellid species overwinter in aggregations consisting of many individuals. They may clump because adults are attracted to particular environmental stimuli and/or of an innate tendency to join conspecific individuals. Aggregation behaviour was studied in Coccinella septempunctata L., which forms small clumps, and Ceratomegilla undecimnotata (Schneider) and Hippodamia variegata (Goeze), which form large clumps. Adults were recorded at five hilltop hibernacula (400-1500 m altitude) in central Europe (50-51°N, 14-16°E) for periods up to 27 years. The hibernacula occur in areas sparsely covered with isolated grass tussocks or completely with stones. Numbers of adults recorded under each of 300-900 stones or among the stems of the grass tussocks were counted every year at each hibernaculum. The degree of aggregation was determined using Taylor's power law. The coccinellid distributions became more aggregated and the size of the aggregations increased as their abundance increased, less in C. septempunctata than in the other two species. Aggregations formed even in the absence of prominent structures, which may attract immigrants, and even when unoccupied stones or tussocks suitable for overwintering were available. Aggregations may be established and their size limited by the strength of the intrinsic preference to join conspecifics. The supposed advantage of aggregated overwintering must be greater than the risk associated with the easy spread of diseases.
For biological control it is necessary to store mass-reared biological control agents when the demand is low. The objective of this study is to increase their shelf life without significantly reducing their fitness. The ladybird Hippodamia variegata is a widespread and voracious aphidophagous predator, with an important role in decreasing the abundance of pest aphids in many parts of the world. We investigated the effect of storage at three temperatures: constant 1°C, constant 6°C, and an alternating thermal regime of 12°C/0°C (the higher temperature for 12 h and the lower one for another 12 h). They were exposed to each of the temperature regimes for either 15, 25, 35, 45 or 60 days. We recorded survival, pre-oviposition period, fecundity and voracity of adult H. variegata following storage. The survival of adult beetles significantly declined with increasing storage duration at all three temperatures. Storage at 6°C up to 35 days and at 12°C/0°C up to 45 days had no significant effects on the fecundity of the ladybirds, but storage for longer significantly decreased fecundity. Beetles stored at 1°C for any of the durations had significantly lower fecundities. Prolonged cold storage caused an increase in the pre-oviposition period at all storage temperatures. Generally, 6°C and 12°C/0°C are the best temperatures for storing the ladybirds as they had the least negative effect on their fitness. The results of this research can help in improving the quality of H. variegata stored for use as biological control agents in the following season.
We asked if the structural heterogeneity of a laboratory arena differentially affected the abandonment of the plot, residence time, locomotory rate, pause duration and turning rate of adult Eriopis connexa and Hippodamia variegata (Coleoptera: Coccinellidae). We simulated an increase in heterogeneity by distributing vertically-oriented toothpicks in a circular arena: one control (without toothpicks), one uniform plot (toothpicks every 1 cm) and one random plot (randomly distributed toothpicks). No food was provided inside the arena. Coccinellids were released individually in the centre of each plot and their movement was videotaped. Fewer H. variegata adults left the plots as these become more heterogeneous. E. connexa did not discriminate between plots in their residence time, but H. variegata remained longer in the uniform and longest in the random plots. H. variegata only stayed longer than E. connexa in the random plots. This resulted because adults of H. variegata were stationary for longer periods, moved more slowly and less linearly and explored a higher number of toothpicks than adults of E. connexa in more heterogeneous environments. Thus, the physical structure of the environment differentially affects the movement patterns of insects. Eriopis connexa seems to be less sensitive to structural heterogeneity than H. variegata.
Lady beetles (Coleoptera: Coccinellidae) are a classical group for studying the mechanisms that determine local and temporal trends in colour polymorphism. Here we report long term trends in variation in the percentage of different morphs in a population of Hippodamia variegata (Goeze) at Štúrovo, Slovakia (47°48´N, 18°43´E). The morphs differ in the number and location of the spots on their elytra. Beetles were sampled from stands of herbaceous plants using a standard method each year in August over a period of 74 years from 1937 to 2011. Twenty two morphs (out of 74 possible) were recorded in a total sample of 6,984 individuals. Four dominant morphs made up 90% of the total sample and varied in their annual frequency independently of one another. Frequency of "pale" morphs (0–3 spots per elytra), supposedly favoured by a warm climate, increased from 1981 to 2000s’ during a period of climate warming, but only after a decrease that took place between 1937 and 1981, which did not parallel a change in climate. Moreover, the differences in the extent of the melanization of the elytral surface are too small to significantly affect thermoregulation in the different morphs. Therefore, the results presented do not provide unequivocal support for climate change determining the long term trends in the variation in the proportions of the different morphs., Alois Honek ... [et al.]., and Obsahuje seznam literatury