Common bee fly (Systoechus vulgaris)

The Common Bee Fly (Systoechus vulgaris) is a species of fly in the family Bombyliidae, commonly known as bee flies. These flies are named for their resemblance to bees, particularly in their appearance and hovering flight behavior. The Common Bee Fly is widespread and found in various parts of Europe and Asia. It plays an important role in ecosystems as both a pollinator and a parasitoid during its larval stage.

Physical Description:

• Size: The Common Bee Fly is relatively small, typically measuring about 6 to 10 mm (0.2 to 0.4 inches) in length.
• Body Shape: Like other bee flies, Systoechus vulgaris has a stout, rounded body covered in dense hairs that make it resemble a small bumblebee. This mimicry helps the fly avoid predation by tricking potential predators into thinking it is a stinging insect.
• Coloration:
• The body is often covered in a dense layer of yellowish or brownish hairs, which give it a fuzzy appearance similar to a bee.
• The abdomen may feature a pattern of dark and light markings, adding to the resemblance to bees.
• Wings: The wings are clear with a dark spot or shading near the front edge. Bee flies are known for their hovering flight, and Systoechus vulgaris is no exception. It can hover in place while feeding on nectar from flowers.
• Proboscis: The Common Bee Fly has a long, slender proboscis used for feeding on nectar. This proboscis is often as long as its body, and the fly uses it to reach deep into flowers to access nectar while hovering in front of them.

Behavior:

• Flight: Systoechus vulgaris is an agile flier and often seen hovering in front of flowers while feeding. It can hover motionless in mid-air and dart quickly between plants. Its flight pattern closely resembles that of bees, making it difficult to distinguish from a distance.
• Feeding: Adult Common Bee Flies primarily feed on nectar and pollen. Their long proboscis allows them to access nectar from deep within tubular flowers. They are important pollinators for many plant species, particularly those with long corollas.
• Mimicry: The bee-like appearance of this fly is an example of Batesian mimicry, where a harmless species mimics the appearance of a more dangerous one (in this case, bees) to avoid predators.

Habitat:

The Common Bee Fly is adaptable to various habitats, often found in:

• Meadows and Grasslands: These open areas with abundant flowering plants are ideal for nectar-feeding bee flies.
• Gardens and Parks: It is often seen in gardens where flowers are plentiful, making it a frequent visitor to urban areas.
• Woodland Edges: Prefers sunlit clearings and edges where it can find both nectar sources and suitable habitats for its larvae.

Life Cycle and Reproduction:

The life cycle of the Common Bee Fly is quite complex, involving both parasitic and nectar-feeding stages.

• Egg Laying: Females lay their eggs near the entrance to burrows or nests of solitary bees and wasps. The larvae are parasitoids, meaning they rely on a host insect to complete their development.
• Larvae: Once hatched, the larvae of Systoechus vulgaris make their way into the nest of their host. They parasitize the bee or wasp larvae by feeding on their stored pollen and nectar, and eventually on the host larva itself. This parasitic relationship ensures the fly larva has a rich source of food while developing.
• Pupation: After fully developing, the larvae pupate and emerge as adult flies the following spring or summer.
• Adult Stage: Adult flies emerge in warm months and immediately begin feeding on nectar, helping to pollinate flowers as they move from plant to plant.

Ecological Role:

• Pollination: Adult Common Bee Flies are important pollinators. Their feeding habits help fertilize flowers, making them an essential part of the ecosystem despite their parasitic larval stage.
• Parasitism: During their larval stage, bee flies play a role in regulating populations of solitary bees and wasps. While this might seem harmful to the individual bees, it is part of a natural balance in ecosystems, as parasitoids help control the populations of other insects.

Distribution:

The Common Bee Fly is found across much of Europe, extending into parts of Asia. Its range includes a variety of climates, from temperate regions to more arid zones, where it adapts to local flowering plants and host insects.

Conservation Status:

The Common Bee Fly is not currently considered at risk, and its populations are generally stable. However, like many pollinators, it can be affected by habitat loss, pesticide use, and climate change, which may impact both the availability of flowers for adults and suitable nesting sites for their host bees and wasps.

Interesting Facts:

• Nectar Thief: Although they are important pollinators, bee flies are sometimes known as “nectar thieves.” This is because their long proboscis allows them to access nectar from flowers without coming into contact with the reproductive parts of the plant, meaning they can sometimes feed without actually pollinating the flower.
• Egg Flinging: Female bee flies are known to fling their eggs into the nests of solitary bees or wasps from a distance, rather than placing them directly inside. This behavior reduces the risk of attack from the host insect.

Conclusion:

The Common Bee Fly (Systoechus vulgaris) is a fascinating insect, known for its mimicry of bees and its complex life cycle involving both pollination and parasitism. As adults, these flies are important pollinators, helping to fertilize a wide range of plants, while their larvae play a role in controlling populations of solitary bees and wasps. Their adaptability to different environments makes them a common sight in gardens, meadows, and other areas with abundant flowers.

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