Few groups of insects have been surveyed over a very long period (50 years or more) in an area. Three groups were considered here meeting the long survey condition: ground beetles (Coleoptera: Carabidae), ground Scelionidae (Hymenoptera) and species of Tenthredo (Hymenoptera: Tenthredinidae). The diversity of ground beetles in agricultural sites around Ottawa (Ontario) and Montreal (Quebec) has been markedly reduced during the 1980s and 1990s. During the same period we witnessed the collapse of other insect groups outside agricultural sites. Species of sawflies of the genus Tenthredo and a group of ground scelionid wasps were clearly affected. The decline is correlated with the presence of a new crop, corn, in these regions with a herbicide spray protocol in late May or early June. Herbicides are not killing insects on contact. Contaminated insects are free to disperse away from agricultural sites to a wide range of habitats where they are preyed upon by insects, spiders and birds. The consumption of contaminated insects by predators is probably behind their population collapse of many species or even the extirpation of some species from the study areas.
Source: Goulet, H. & Masner L. (2017) J Biodiversity Volume 18 - Issue 2-3: Food, Agriculture and Biodiversity
http://www.tandfonline.com/doi/full/10.1080/14888386.2017.1351398?scrol…
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