Sunday, September 3, 2017

Imitation is the Best Form of Protection in Some Cases

Not a bee, but a mimic, the fly Eristalis© Beatriz Moisset
A stroll among the flowers allows me to see numerous bees of different sorts, zipping along from blossom to blossom. Just as numerous are other winged insects that look very much like bees. The experienced eye recognizes them for what they are, flower flies impersonating the stinging insects. But those unfamiliar with bees or with insects, in general, may assume that these flower flies are bees. They may even recoil in fear of a sting although the flies are innocuous, lacking such powerful weapon.

A wasp mimic, Spilomyia sayi © Beatriz Moisset
Those flies who imitate bees or wasps have a reason for playing this masquerade. They are not interested in fooling us, humans. Their deception is aimed at their predators, mostly birds. However, the ruse is so effective that it even we fall for it.

Syrphid flies, also known as flower flies or hover flies, are almost as assiduous in visiting flowers as bees are. They drink nectar and sometimes also feed on pollen. Although not as efficient as bees as pollinators, they deserve some credit and occasionally their contribution to pollination is significant. Another group of flies that visit flowers with great frequency includes the so called bee flies.

Both, flower flies and bee flies mimic bees or, in some instances, wasps. The imitation is very specific in some cases. The so called drone fly, Eristalis tenax, looks like a honey bee. The name is appropriate, considering that male honey bees, drones, have large eyes, and these flies have even bigger eyes. Both, the fly and the honey bee are European. The imitator evolved along with its model in that continent. Another European flower fly that mimics honey bees effectively is the narcissus fly, Merodon equestris.

Other flower flies and also a robber fly imitate bumble bees. They have a furry coat and even buzz like bumble bees.

Bumble bee mimic, Mallota bautias © Beatriz Moisset
The smaller flies, members of the Syrphinae subfamily apparently are mimics of some or another of the many solitary bees. In most cases one cannot be sure of the model chosen for this mimicry.

A honey bee, the model for many mimics © Beatriz Moisset
It is a peculiar thing that some imitations are extremely good, while others are rather general in character. Biologists speculate that even a not-so-good imitation may serve the purpose of deceiving the enemies and this is why such types of mimicry persist in nature. It is also possible that the predators don’t see exactly what we see and the mimicry is convincing enough for them.

This is just one type of mimicry. Other insects take the appearance of their surroundings, which makes them nearly invisible. Still others look like bird poop, not an appetizing sight for a snack seeker. Stay tuned for descriptions and illustrations of more of these ingenious survival mechanisms.


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