When we think of pollinating insects, honeybees and bumblebees are the first things that come to mind. Nevertheless, other insects, including some scarab beetles, ants and wasps, and not forgetting several fly species, transport pollen from one flower to another, in the process ensuring that pollination takes place. Among pollinating flies, syrphid flies and bee flies are certainly the ones most observed during the summer months, on flowers in parks and gardens.
Syrphid flies: vividly colored, fast-flying insects that love flowers!
Syrphid flies (Syrphidae) or flower flies are small elongated or sturdy insects that vary in size from 3 to 25 millimeters. They generally have a large head, big eyes and short antennae. Their black or brown bodies, often colored with yellow or orange bands, are reminiscent of those of honeybees, wasps and bumblebees. Their beauty, their colors and their great diversity make some amateurs (and professionals) refer to them as the “butterflies” of the fly world. And they’re also highly popular with insect photographers. Syrphid flies flap their wings extremely quickly. Capable of hovering immobile for minutes at a time, they can back away from one flower and then dart to another one in an instant. Some syrphids rank with the finest flying insects in the animal kingdom.
The larvae of a number of syrphid species have a huge appetite and can eat hundreds of aphids a day. Moreover, it’s not unusual to spot larvae of the Syrphus genus feeding on the leaves of ornamental plants and shrubs in our gardens.
Bombyliidae: aerodynamically shaped flies!
Hardier than the syrphids, bee flies (Bombyliidae) often have a long, very straight proboscis towards the front of the head. Capable of hovering, they easily insert their little trunks into flowers, a bit like a hummingbird, looking for nectar. The bodies of many species are densely covered with fine bristly hairs that make them look like little balls of fluff, yellow, white or brown, equipped with a pair of wings.
In many species of bee flies, the female fills a small pouch located at the base of her abdomen with fine sand in order to wrap up her eggs before they’re laid. Thus concealed, the eggs are dropped to the ground, very close to the entrance to the nests of honeybees or solitary wasps. When it leaves the egg, the little larva, highly mobile, infiltrates one of those hymenopterans’ nests and feeds on the pollen stored in the nest for its host. After shedding its skin, the larva then parasitizes the larvae of the bee or the wasp still present in the nest. Larvae of the great majority of bee fly species are parasites on other, ground-dwelling, insects such as grasshoppers and caterpillars. They contribute to control various insect populations.
Efficient pollinators worth knowing better!
Syrphids and bee flies forage on a great variety of plant species. In an agricultural environment, syrphids moreover play an important role as pollinators of a number of cash crops, including cranberry, carrot, cauliflower, mustard, colza and apple. Unlike honeybees and bumble bees, these flower-loving flies don’t collect nectar and pollen for their offspring, and that being the case, they scatter the pollen as they move from one flower to the next. Unfortunately, syrphids and bee flies are often excluded from studies about pollinators. As a result, their role as flower visitors is poorly understood. Their presence in our living environments, as predatory or pollinating insects, would therefore be worth examining and being recognized for its value, both in urban areas and agricultural surroundings.