Environmental parameters in the semi-natural condition and diapause incidence of flesh fly

Seasonal changes in temperature and day length are distinct between rural
and urban areas due to urban warming and the presence of artificial light
at night. Many studies have focused on the impacts of these ubiquitous
signatures on daily biological events, but empirical studies on their
impacts on insect seasonality are limited. In the present study, we used
the flesh fly Sarcophaga similis as a model insect to determine the
impacts of urbanisation on the incidence and timing of diapause
(dormancy), not only in the laboratory but also in rural and urban
conditions. In the laboratory, diapause entry was affected by night-time
light levels as low as 0.01 lux. We placed fly cages on outdoor shelves in
urban and rural areas to determine the timing of diapause entry; it was
retarded by approximately four weeks in urban areas relative to that in
rural areas. Moreover, almost all flies in the site facing an urban
residential area failed to enter diapause, even by late autumn. Although
an autumnal low-temperature in the urban area would mitigate the negative
effect of artificial light at night, strong light pollution seriously
disrupts the flesh fly season adaptation.