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1. Global warming is occurring at an unprecedented rate. Information about how variable temperature affects insect life‐history traits is still scarce. 2. The current study first evaluated the effects of two variable‐temperature treatments [high‐temperature‐variation (HT) treatments and mild‐temperature‐variation (MT) treatments] on the life‐history traits of a maternal generation (F0) of Rhopalosiphum padi, a serious global pest, using a constant normal‐temperature (NT) treatment as a control. Following this, the life‐history traits of the offspring generation (F1) under the NT, MT and HT scenarios were analysed. 3. The total developmental duration of the aphid F0 generation was significantly shortened by MT treatments, while it was significantly increased by HT treatments. Adult longevity and the fecundity of F0 were significantly decreased by HT treatments compared with those in the MT and NT treatments, whereas no significant difference was found between the latter two treatments. The HT treatments applied to the F0 generation significantly prolonged the total developmental duration of the F1 generation. The offspring adult longevity was not affected by the mothers' temperature experience. The offspring fecundity was significantly increased when the F0 generation experienced MT treatments. The intrinsic rate of increase (rm) was significantly decreased when the F0 generation experienced an HT scenario. However, the MT scenario experienced by the F0 generation did not significantly affect the rm of their offspring. 4. The results will provide new insights into the effects of variable maternal temperature on the individual development and population dynamics of offspring under a global warming scenario.

Aphids use their visual systems to detect information about the external environment, and visual genes are likely to have a role in host plant searching and environmental adaptation. Yet, there is little understanding of the presence and expression of visual opsin genes in aphids. In this study, we cloned and identified four vision‐related genes (LW‐OPN, UV‐OPN1, UV‐OPN2, and rhodopsin) from a cosmopolitan serious cereal pest, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), and evaluated their expression patterns. Transcription of the four genes was detected at all developmental stages. The inducing conditions (short photoperiod and low temperature) significantly affected the expression of the UV‐OPN1 and rhodopsin genes. The highest levels of transcription of all genes were observed in males, and the lowest in oviparae. The expression levels in wingless virginoparae were markedly lower than those in gynoparae and winged virginoparae. The starvation treatments resulted in a decline in the survivorship of adults. The mortality rates increased with increasing duration of starvation. The four genes tended to be upregulated following starvation for 24 h, and their expression levels were considerably decreased after subsequent feeding. These results are of importance for further understanding the evolution and function of visual opsins in aphids.

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Armyworm feeding in large, destructive groups is hugely difficult to control and the oriental armyworm, Mythimna separata (Walk), is one such pest. In this study, we reported a semisynthetic artificial diet for the oriental armyworm. This diet is based on Ritter’s diet, a formula developed for Heliothis zea. The survival of M. separata was extremely low and only around 2% insects can reach the adult stage on Ritter’s diet. But, it can reach up to 100% if corn leaf powder (CLP) was mixed, and insects grew faster and gained more mass. After testing a set of mixtures of Ritter’s diet and CLP, we found that 14.3% was the optimal proportion of CLP for making the artificial diet. We then used chloroform to extract CLP. Insect performance was still much better on Ch-extracted CLP diets than that on Ritter’s diet, but it was poorer than that on the diets containing unprocessed CLP, suggesting that the essential factor(s) was only partially extracted from corn leaf. We then used methanol and dichloromethane, two solvents differing in their polarity, to process the extractions and analyzed the extracted chemicals using gas chromatography–mass spectrometry (GC-MS). Insects had a better performance on dichloromethane-extracted CLP diet in comparison to methanol-extracted one, indicating that the important factor(s) is more prone to methanol extraction. The reported recipe here is useful for the research on M. separata and possibly other grain-crop eating armyworms. The functions of the chemicals extracted from corn leaf tissue can be investigated in the future studies.