Temperature during pupal development affects hoverfly developmental time, adult lifespan and wing length

Hoverflies (Diptera, Syrphidae) are cosmopolitan, generalist flower
visitors and among the most important pollinators after bees and
bumblebees. The dronefly Eristalis tenax can be found in temperate and
continental climates across the globe, often synanthropically. Eristalis
tenax pupae of different generations and different climate zones are thus
exposed to vastly different temperatures. In many insects, the ambient
temperature during the pupal stage affects development, adult size, and
survival; however, the effect of developmental temperature on these traits
in hoverflies is comparatively poorly understood. We here reared E. tenax
pupae at different temperatures, from 10°C to 25°C, and quantified the
effect on adult hoverflies. We found that pupal rearing at 17°C appeared
to be optimal, with high eclosion rates, longer wings, and increased adult
longevity. Rearing temperatures above or below this optimum led to
decreased eclosion rates, wing size, and adult survival. Similar thermal
dependence has been observed in other insects. We found that rearing
temperature had no significant effect on locomotor activity, coloration or
weight, despite evidence of strong sexual dimorphism for each of these
traits. Our findings are important as hoverflies are key pollinators, and
understanding the effects of developmental temperature could potentially
be useful for horticulture.