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In the original publication of the article, the second last sentence in the abstract was published incorrectly. The sentence “it is possible to turn aphids from red back to green within a few days, and from green back to red within a couple of weeks (low-to-high and high-tolow light intensities, respectively)” should read as “it is possible to turn aphids from green back to red within a few days, and from red back to green within a couple of weeks (lowto- high and high-to-low light intensities, respectively)”. The original article has been corrected.

The occurrence of different color patterns in a population of a species can depend on genetic variations or plasticity to environmental conditions. Body color variation is under selection because it is involved in several ecological processes such as camouflage for prey-predator interactions or resistance to environmental variations. Among insects, aphids are known to produce different body-color morphs depending on their biotic and abiotic environments and their bacterial endosymbionts. The English-grain aphid (EGA) Sitobion avenae produces both red and green morphs in cereal fields. Using both field studies on the Canadian prairies (Saskatchewan) and laboratory experiments, we aimed to study the mechanisms that trigger plasticity in body coloration to better understand the ecological role of body coloration and color-change evolved by animals, including aphids. We first analyzed green and red morph EGA distribution on wheat ears in different fields and showed that red aphids were mostly located at the top of the ear and green aphids at the bottom. Then, using DNA sequencing, we showed that red and green morphs did not strongly differ in their bacterial endosymbiont composition and abundances. Finally, using a climate-chamber setup in the laboratory, we highlighted that EGA body-coloration is under light-intensity control and that it is possible to turn aphids from green back to red within a few days, and from red back to green within a couple of weeks (low-to-high and high-to-low light intensities, respectively). Light-intensity-controlled color-change likely results in adaptive plasticity in response to shifts in environmental conditions that can occur over the lifespan of an aphid, and is fully reversible, even at the adult stage.

In agricultural areas, the climatic conditions at the northern limit of crop cultures could impact pest regulation. In this paper, we study the aphid-parasitoid-hyperparasitoid network in cereal fields around Saskatoon (SK, Canada), one of the most harsh climatic conditions for cereal crops in the world, with an extremely short growing season. We have inves- tigated the aphid-parasitoid-hyperparasitoid species relative abundances over two consecutive years. In 2014, a cold spring year, aphids were only found late in the growing season, and their arrival probably corresponded to late Southern winds. In 2015, aphids, parasitoids and hyperparasitoids arrived in the cereal fields in July and August, whereas the cereal harvest is typically complete by the end of the month of August. Three species of primary parasitoids were found for a total parasitism rate of 7.62%, and four genera of hyperparasitoids, with a hyperparasitism rate of 20.1%. There were 87.4% apterous aphids, and the proportion of apterous and winged (alate) aphids did not differ among the 3 aphid species, or among use by parasitoid species and hyperparasitoid species. The sex ratio of parasitoids in the complex was biased towards females for most of the species. In areas with extreme weather conditions and short growing seasons, effective biocontrol through para- sitism is limited, although the synchronization level of parasitoids to their aphid hosts is high. We discuss the consequences of the limited length of the growing season on the provision of ecosystem services and on the seasonal ecology of insects of agronomic interest. We also provide information about morphological criteria for identification of parasitoids from the genus Aphidius.