Juvenile hormone regulation on the flight capability of Bactrocera dorsalis (Diptera: Tephritidae)

The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is considered a major economic threat in many regions worldwide. In order to better understand the flight capacity of B. dorsalis and its physiological basis, the functions and regulatory roles of juvenile hormone (JH) in the flight muscle of B. dorsalis were studied under a controlled environment. JH titer of B. dorsalis varied with age and sex. Females, irrespective of age, have higher JH than males for ovarian development and maturation in addition to better flight capabilities. The flight duration and distance of both males and females increased with the gradual increase of JH titer after adult emergences. JH titer peaked in 15-d-old adult and declined subsequently with age. Flight activity stimulated the production of JH as adults flown for 24 hours on the flight mills have the highest JH titers compare to adults tethered on shorter flight durations. Furthermore, JH III-treated adults were able to perform long-duration and long-distance flights. The mutual reinforcement of JH and flight activity provides fundamental understanding on the physiological aspects of the flight capability and dispersal, which facilitates strategies for the long-term control of this destructive pest.

Effect of Sex and Air Temperature on the Flight Capacity of Bradysia odoriphaga (Diptera: Sciaridae)

Bradysia odoriphaga Yang & Zhang (Diptera: Sciaridae) is an important pest of Chinese chives. Information on the effects of biotic and abiotic factors on the flight performance of B. odoriphaga is crucial for understanding the pest’s ability to disperse and migrate. In this study, the effects of sex and air temperature on the flight performance of B. odoriphaga imagoes were assessed by tethering individual imagoes to computerized flight mills for a 10-h experiment. The results showed that the percentage of imagoes that flew a particular distance gradually decreased as flight distance increased. The percentage of imagoes was significantly higher for males than females when the flight distance was <300 m. Sex and air temperature significantly affected average flight time (which ranged from 14.6 to 68.3 min) and average flight distance (which ranged from 10.4 to 107.2 m), but did not significantly affect average flight speed (which ranged from 3.8 to 6.4 m/min). For both females and males, the average flight distance and flight time were shortest at 18°C and longest at 22°C; the interaction between air temperature and sex was not significant. The results suggest that B. odoriphaga has a poor potential for long-distance migration. These findings will be helpful for developing forecasting and management systems for B. odoriphaga.

Pesticide exposure affects flight dynamics and reduces flight endurance in bumblebees

The emergence of agricultural land use change creates a number of challenges that insect pollinators, such as eusocial bees, must overcome. Resultant fragmentation and loss of suitable foraging habitats, combined with pesticide exposure, may increase demands on foraging, specifically the ability to reach resources under such stress. Understanding the effect that pesticides have on flight performance is therefore vital if we are to assess colony success in these changing landscapes. Neonicotinoids are one of the most widely used classes of pesticide across the globe, and exposure to bees has been associated with reduced foraging efficiency and homing ability. One explanation for these effects could be that elements of flight are being affected, but apart from a couple of studies on the honeybee, this has scarcely been tested. Here we used flight mills to investigate how exposure to a field realistic (10ppb) acute dose of imidacloprid affected flight performance of a wild insect pollinator - the bumblebee, Bombus terrestris audax. Intriguingly, intial observations showed exposed workers flew at a significantly higher velocity over the first ¾ km of flight. This apparent hyperactivity, however, may have a cost as exposed workers showed reduced flight distance and duration to around a third of what control workers were capable of achieving. Given that bumblebees are central place foragers, impairment to flight endurance could translate to a decline in potential forage area, decreasing the abundance, diversity and nutritional quality of available food, whilst potentially diminishing pollination service capabilities.Summary StatementAcute neonicotinoid exposure impaired flight endurance and affected velocity of Bombus terrestris workers, which may dramatically reduce colony foraging potential and pollination provision in pesticide applied landscapes.

Higher flight activity in the offspring of migrants compared to residents in a migratory insect

Migration has evolved among many animal taxa and migratory species are found across all major lineages. Insects are the most abundant and diverse terrestrial migrants, with trillions of animals migrating annually. Partial migration, where populations consist of resident and migratory individuals, is ubiquitous among many taxa. However, the underlying mechanisms are relatively poorly understood and may be driven by physiological, behavioural or genetic variation within populations. We investigated the differences in migratory tendency between migratory and resident phenotypes of the hoverfly, Episyrphus balteatus , using tethered flight mills. Further, to test whether migratory flight behaviour is heritable and to disentangle the effects of environment during development, we compared the flight behaviour of laboratory-reared offspring of migrating, overwintering and summer animals. Offspring of migrants initiated more flights than those of resident individuals. Interestingly, there were no differences among wild-caught phenotypes with regard to number of flights or total flight duration. Low activity in field-collected migrants might be explained by an energy-conserving state that migrants enter into when under laboratory conditions, or a lack of suitable environmental cues for triggering migration. Our results strongly suggest that flight behaviour is heritable and that genetic factors influence migratory tendency in E. balteatus . These findings support the growing evidence that genetic factors play a role in partial migration and warrant careful further investigation.

The effect of cold storage of mass-reared codling moths (Lepidoptera: Tortricidae) on subsequent flight capacity

Flight capacity of codling moths, Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae), was measured with computer-linked flight mills following exposure to one of two temperature regimes. Codling moth adults were held for 24 hours before flight under either chilled (2 °C) or unchilled (24 °C) conditions. The chilling treatment emulated conditions that codling moths are exposed to pre-release in the Okanagan Sterile Insect Release (SIR) Programme. Moths were assayed on flight mills for eight hours to obtain a measure of flight capacity based on total flight distance. Energy use was assessed by weight loss during flight and post-flight body lipid content compared with similarly treated moths that did not fly. Flight distance did not vary with pre-flight temperature treatment, however moth pre-flight weight influenced flight capacity; heavier moths flew further. Moths chilled before the bioassay used less energy based on reduced weight loss and higher lipid content post bioassay as compared with unchilled moths. The current cold storage procedure used in the SIR Programme does not negatively influence subsequent flight capacity and reduces energy use during flight. Codling moths can fly on average between 7–10km in an eight-hour flight mill bioassay and lipids, at least in part, are used to fuel flight.