Tuesday, August 23, 2016

Mimicry: Things are not always as they seem

I recently posted the photo above, along with the message below, to Facebook:

A friendly public service announcement on behalf of America's flower flies (family Syrphidae). Those little bee-like insects (such as in the photo) that sometimes land on you are not bees. They are valuable, pollinating flies that do a good job of mimicking bees. While they do have a tendency to land on people's skin - seeking minerals in your sweat - they cannot sting, bite or otherwise hurt you. Pancaking them, or dousing one's self with insect repellent is not necessary. I only say this because I've seen about six people in the last week overreacting to the "aggressive bees".

Apparently it was of help to the flies, as the message got a lot of attention. This experience got me to thinking about the broader picture of mimicry, one of my favorite subjects in all of natural history. The flower fly (or hover fly) does a darn good job at looking like something that might sting, thus theoretically dissuading would be predators from attacking. But flower flies are just the tip of the iceberg when it comes to insects mimicking the appearance of Hymenoptera (bees and wasps) that pack a punch.

A few examples follow...

A homicidal looking "bumblebee" if there ever was one. This is a robberfly, Laphria thoracica, sitting on a conspicuous perch awaiting insect prey to fly by. When a suitable victim makes an appearance, the fly will whir out after it, grab the meal to be with spiny legs, and stab it with a syringelike proboscis. The fly then injects chemicals that paralyze the victim and speed in the decomposition of its innards, the latter of which will eventually sucked out via the fly's proboscis.

Why look like a bumblebee? Possible because robberflies are prone to perching out in the open, and looking like something that stings may telegraph a message of AVOID to birds.

If you weren't privy to this one, it'd make you head the opposite direction, perhaps. This is a very large fly known as a Mydas Fly, Mydas clavatus. They greatly resemble large predatory spider wasps, but are completely harmless. Their larvae dwell in decomposing wood and are predators of beetle larvae. The ferocious looking wasp-mimicking adult flies apparently only take nectar from flowers.

The first time I saw a Thick-headed Fly in the genus Physocephala (I think this is P. tibialis), it completely fooled me. I was sure it was a wasp. It has a waspish "waist" and thickened terminal abdomen, and even waves its front legs around when perched in the manner of some wasps. This species is reportedly a parasitoid of the bumblebee Bombus bimaculatus.

Beetles are in on the let's look like something dangerous act, too. This is an Amorpha Borer, Megacyllene decora, and the adults really look like a hornet, especially in flight.

This one may take the cake, if we're interpreting the disguise properly. It is another beetle, the Delta Flower Scarab, Trigonopeltastes delta. John Howard introduced me to this beauty, which if you are lucky, can be found visiting flowers such as this rattlesnake-master, Eryngium yuccifolium. John noted that when the beetle is flushed, it flares its wings in such a way that the pattern forms a large scary wasplike face - two big brown eyes and white mandibles below those. Hmmm...

Another great hornet mimicking beetle, the Locust Borer, Megacyllene robiniae, which is common on goldenrods in fall.

Even moths - yes, MOTHS! - get in on the act. This is the Eupatorium Borer, Carmenta bassiformis (I believe). It, and its fellow borers in the family Sesiidae are fabulous actors, greatly resembling bees and wasps.

A Squash Vine Borer, Melittia cucurbitae, visits the flowers of dogbane, Apocynum cannabinum. This day-flying moth would fool just about anyone into thinking it is some sort of wasp. It even dangles is its legs, which are thickened with brushes of hair, as it flies just as many wasps do.

Here we have a dragonfly, of all things, seemingly mimicking the look of a bee/wasp/hornet sort of thing. This is a female Elfin Skimmer, Nannothemis bella, the smallest dragonfly in North America. Only the female apparently employs the mimicry; males look very different. She even twitches her abdomen when at rest, in the manner of some bees. When seen in the field, the effect is strikingly wasplike.

Finally, at the end of this short list of mimicry examples is the utterly bizarre mantisfly known as Climaciella brunnea. Squint your eyes a bit and ignore some of the odd appendages, and this thing is the spitting image of paper wasps in the genus Polistes. These wasps certainly pack a punch, and I'd imagine potential predators learn a painful lesson if they try and capture and eat them. If you can look like a paper wasp, a la this mantisfly, they'll presumably leave you alone too. Mantisflies are a story in their own right, and I've written about them HERE.

Sometime I'll have to write about all the creatures that mimic bird droppings.


1 comment:

Lisa Rainsong said...

What a splendid collection! I really enjoyed the way you put all these together under one topic. Of course, I'm sure everyone will be eagerly awaiting the bird-dropping mimics as well.