Bombylius major (commonly named the large bee-fly, the dark-edged bee-fly or the greater bee fly) is a parasitic bee mimic fly. Bombylius major is the most common type of fly within the Bombylius genus. The fly derives its name from its close resemblance to bumblebees and are often mistaken for them.

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Bombylius major exhibits a unique flight behavior known as “yawing” and plays a role in general pollination, without preference of flower types. The fly does not bite, sting, or spread disease. However, the fly uses this mimicry of bumblebees to its own advantage, allowing close access to host solitary bee and wasp nests to deposit its eggs. After hatching, the larvae find their way into the nests to parasitically feed on the grubs.

Flight

It has been discovered that the fly is capable of a unique behavior, which was discovered with the use of a high speed camera. In this behavior, the flies are seen to rotate around a vertical axis as they fly (this action is known as “yawing”). However, it is still unknown what can cause this behavior to be triggered and what purpose it serves, but a proposed explanation includes mating habits. Here is an illustration of “Yaw” in the context of an airplane…substitute the fly body with head facing forward (to left).

Pollinator Role

The Bombylius major bee-fly is a common, generalist floral pollinator, meaning that it does not give preference to one flower over another, instead pollinating a wide variety of plant families and species. The fly uses its proboscis to carry and transfer the pollen. The species is a dominant pollinator within its community, sometimes even pollinating up to two thirds of the local flowers. In addition, Bombylius major will visit and pollinate plants that attract few other species. Some types of flowers, for example Pulmonaria officinalis, will be almost exclusively pollinated by Bombylius major, with other species contributing a negligible amount to that plants pollination. Some flower species, such as Delphinium tricorne, are even specifically adapted to the fly in terms of color, shape, and form. If given the choice, Bombylius major will have a consistency in plant choice.

Flower Attraction

Long distance floral attraction is governed by optical sense, with color being the most important factor. The flies are typically more attracted to blue and violet colors, and occasionally yellow, over orange and pink. However, short distance floral attraction is based on the fly’s olfactory sense.

Sunbathing Activity

The fly is mostly active during day hours when the weather conditions are warm and sunny. Bombylius major is attracted to sunnier places and is more likely to pollinate these areas, with a larger average of flower visits in areas of higher amounts of sunshine. The fly will hide in the trees during the night and usually dart away from a cast shadow and occasionally hide in clean washing brought in fresh from the washing line and fly out causing unsettled behavior in the discoverer.

Flower Description

Claytonia caroliniana is a flowering, woodland perennial herb. It grows from March though June and is one of the earliest spring ephemerals. The plant grows from spherical underground tubers in light humus. They sprout and bloom before the tree canopy develops. Once the area is shaded, the plants whither leaving only the tuberous roots underground.

The plant is edible, but its usability is limited due to difficulty harvesting and the small quantities each plant produces. Its tuberous roots are edible and rich in starch and can be cooked or eaten raw. The leaves can be eaten as well. The tuberous roots are eaten by eastern chipmunks and white-footed mice.

Source: Wikipedia “Bombylius major ” and “Claytonia caroliniana. Direct quotations are in italics.

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