Morphometric traits and body weight are often used to study changes in fitness. For the invasive alien maize pest, Diabrotica virgifera virgifera LeConte, little information is available regarding the possible relationship between morphometric traits and adult activity, which reflects the ability to disperse and invade. Flight and crawling activities of D. v. virgifera adults were investigated in relation to six different morphometric traits as well as body weight, sex and age. This laboratory study revealed that flight activity of D. v. virgifera differed between sexes and changed with age. Young adults of both sexes flew more frequently and took off faster than mature adults. Males flew more frequently and took off faster than females, regardless of age‐class. No such differences were found for crawling frequency, but young males crawled faster than young females. Further analysis revealed that fresh body weight and morphometric traits of young adults were better predictors of flight and crawling activity than the same measurements made on mature adults. Particularly pronotum and elytra measurements on young adults are recommended for bioassay studies on activity parameters of D. v. virgifera.

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of cultivated corn in North America and has recently begun to invade Europe. In addition to crop rotation, chemical control is an important option for D. v. virgifera management. However, resistance to chemical insecticides has evolved repeatedly in the USA. In Europe, chemical control strategies have yet to be harmonized and no surveys of insecticide resistance have been carried out. We investigated the resistance to methyl‐parathion and aldrin of samples from nine D. v. virgifera field populations originating from two European outbreaks thought to have originated from two independent introductions from North America. Diagnostic concentration bioassays revealed that all nine D. v. virgifera field populations were resistant to aldrin but susceptible to methyl‐parathion. Aldrin resistance was probably introduced independently, at least twice, from North America into Europe, as there is no evident selection pressure to account for an increase of frequency of aldrin resistance in each of the invasive outbreaks in Europe. Our results suggest that organophosphates, such as methyl‐parathion, may still provide effective control of both larval and adult D. v. virgifera in the European invasive outbreaks studied.

Via plant volatiles, herbivorous insects locate hosts, find food, and release spawn for better survival and reproduction. Moreover, plant volatiles not only regulate the synthesis and release of sex pheromones in insects but also help them in the search and orientation of sources of sex pheromones. However, after prolonged exposure to plant volatiles, the changes mediating the mating behavior of diamondback moth (DBM) [Plutella xylostella (L.) (Lepidoptera: Plutellidae)] are unclear. DBMs were treated with allyl isothiocyanate, a volatile from cruciferous vegetables; however, it did not improve the mating rate and had a limited effect on mating rhythm. Moreover, the treatment inhibited mating behaviors in 3-day-old DBMs and decreased mating time in 5-day-old DBMs. After prolonged exposure to allyl isothiocyanate, the total mating time of DBM was not significantly different from that after prolonged exposure to n-hexane (control). However, the longest mating time after emergence in DBM after prolonged exposure to allyl isothiocyanate was delayed by 1 day compared with the exposure to n-hexane. Prolonged exposure to plant volatiles intensified the response behavior of DBM to sex pheromones; however, the content of Z11-16: Ald, a major component of sex pheromones, in female DBM gonads exhibited no change. Pheromone biosynthesis activating neuropeptide gene (PBAN) was downregulated in DBMs after prolonged exposure to plant volatiles. These findings suggested that prolonged exposure (6 h) to plant-derived volatiles has little effect on the mating behavior of DBM. The study provided practical guidance for applying phytochemicals in pest control by regulating insect behavior.