Trophic Ecology Drives Annual Variation in Abundance of Aphidophagous (Coccinellidae, Coleoptera and Chrysopidae, Neuroptera) and Phytophagous (Noctuidae, Lepidoptera) Insects: Evidence From Light Traps

Abstract

Abstract Using seventeen-year records of daily light trap catches of predatory Neuroptera (Chrysopidae, 13 species) and Coleoptera (Coccinellidae, 10 species), and of phytophagous Lepidoptera (Noctuidae, 79 species) we tested a hypothesis predicting that the range of annual fluctuations of catch size is greater in aphidophages, whose diet occurs irregularly and locally, than in phytophages, whose diet is available regularly and abundantly. The ranges of fluctuations of annual catches measured as the coefficient of variance (standard deviation expressed as a percentage of the average) of detrended annual catches were significantly greater in Chrysopidae (84 ± 7.1%) and Coccinellidae (121 ± 14.0%) than in Noctuidae (66 ± 2.6%). The difference between aphidophages and phytophages remained when we tested differences between the former and the samples of Noctuidae consisting only of those species whose characteristics (abundance, length and timing of flight period, number of generations per season, overwintering stage) were the same as in aphidophages. Similarly, no differences were found between sets of Noctuidae species that have characteristics (abundance, voltinism, period of flight activity) similar to aphidophages and sets of Noctuidae species that have contrary characteristics. Flight abilities of aphidophages are smaller than those of Noctuidae. As a result of this difference a light trap collects populations of aphidophages from a smaller area than populations of Noctuidae. Thus the extent of fluctuations of catch size of aphidophagous and phytophagous species is influenced both by annual differences in food availability and by differences in size of the area from which the individuals assembling to the light source are recruited.