Hover Fly (Spilomyia longicornis) visiting Eupatorium altissimum (Asteraceae) filmed in Georgia State Botanical Gardens, Athens, GA, USA on September 16th, 2012. Submitted as a short observation.
When we talk about pollination bees immediately occupy our imagination almost as a cerebral Pavlovian reflex. Flies are big component of the insect pollinators yet they rarely get peoples attention. The insect family Syrphidae (aka syrphid flies) has more than more than 6000 species categorized in 200 genera worldwide. They stand out with their striking bee-mimicing yellow striped colors. It appears visual resemblance into a bee confers a survival advantage. Those who look like bees and wasps survive better. Here you can see a syrphid fly visiting the flowers of the Eupatorium altissimum belonging to the Daisy family (Asteraceae).
The bee/wasp mimicry here is not only limited to the coloration but also movement linked to the behavior of the model. The ends of the front legs are black different from the rest. When in a defensive posture these legs move to the front of the head and are waved around to imitate the long antenna that would be found on a bee or wasp. This sort of movement is an example of behavioral mimicry.
Syrphid flies can be biocontrol agents. Hover fly larvae are predators of many insects gardeners dislike, including aphids and the leafhoppers. These pests can spread diseases such as curly top.
3 Comments
notice the ends of the front legs that are black unlike the other legs. When in a defensive posture these legs move to the front of the head and are waved around to imitate the long antenna that would be found on a bee or wasp. This is known as behavioral mimicry. Note also that the wings move alternately back ad forward. It reminds me of how a tight rope walker might use a pole to keep stable. The wing too are colored in a way that imitates bee, appearing dark in front and lighter behind, as though there were two wings. I also noticed the middle leg missing on the right side that does not appear to hamper this fly in any way. I am sure that there is a lot more information that can be gleaned from this amazing shot.
This is a great piece of information! Mimicry here then is not only limited to looks but also movement linked to the behavior of the model. I was trying my best not to disturb the fly while filming. I am glad it didn’t give away my presence by the defensive false-antenna stance through the front legs as you have described.