Marmalade Hover Fly

The upper side of the abdomen is patterned with orange and black bands. This color pattern may appear wasp-like to other animals, such as birds, protecting it from predation – an example of Batesian mimicry. The percentage of black and yellow color can vary between individuals, and it is modulated by the length and temperature of the pupal period. Females tend to be darker than males. Two further identifying characteristics are secondary black bands on the third and fourth dorsal plates and faint greyish longitudinal stripes on the thorax. As in most other hoverflies, males can be easily identified by their holoptic eyes, i.e., at the top of their heads their left and right compound eyes are touching.

Episyrphus balteatus can be found throughout the year in various habitats, including urban gardens, visiting flowers for pollen and nectar. They often form dense migratory swarms, which may cause panic among people for their resemblance to wasps. In controlled experiments, adults of E. balteatus tend to prefer smaller, yellow flowers, with high concentrations of nectar. Adult E. balteatus, while not as efficient as honey bees, are significant and abundant pollinators. The larva is terrestrial and feeds on aphids – for this reason, E. balteatus is considered one of the main natural enemies of cereal aphids. In the wild, an E. balteatus larva can consume up to about 400 aphids before pupating.

Migration. E. balteatus is a partially migratory species – it is one of the migrating hoverflies along other common species such as Eupeodes corollae. Some individuals migrate from northern Europe to southern Europe and north Africa in autumn, seeking warmer climates to spend the winter, while other adult females can overwinter. It is uncertain if this behavioural difference is controlled genetically; a study in 2013 found no genetic difference between overwintering and migrating populations, while a study in 2018 found evidence of heritability. Transcriptomic analysis discovered that at least 1543 genes are differentially expressed between overwintering and migrating individuals. …