A Case of Predator Mimicry in the Bee Fly Genus Epacmus? (Diptera: Bombyliidae)

In the course of photographing insects in Colorado Springs, Colorado, USA, at a nearby vacant expanse of prairie, soon to be a new housing development, I stumbled upon something interesting. Not until I got home and reviewed my images did I recognize something startling on an otherwise ordinary little bee fly in the genus Epacmus (assuming my identification is correct). Whether this has been documented before I do not know, but the phenomenon is well known in other insects.

Epacmus sp. bee fly. Nothing to see here....yet

Predator mimicry, or elusive mimicry, or aggressive mimicry, is when a prey species mimics one of its predators. This is probably a more widespread strategy than we currently recognize because we are not at the same scale as the predator and prey, and cannot easily interpret what constitutes such mimicry. We do not even enjoy the same perspective, so rarely experience the full effect.

It was not formally recognized, or at least not published, until 2006, that metalmark moths in the genus Brenthia have underside wing patterns that greatly resemble the face and legs of an oncoming jumping spider. They eye arrangement, chelicerae (jaws), and front two pairs of legs are all illustrated on the wings of the moth, when properly displayed by the insect. The moth would make an easy meal for the spider, but not if it presents the illusion that it is a spider. Evolutionary genius.

Spider mimicry is also exploited by other insects, including some fruit flies (family Tephritidae) and planthoppers (Fulguroidea). The bold patterns on the wings of some fruit flies greatly resemble the leg posture of some spiders. Some of the flies enhance the graphic imagery by moving their wings deliberately in a manner utterly convincing of a spider’s movements.

Whoah! Spider eyes and "mustache"

This brings me to the little bee fly I noticed on flowers in that prairie habitat. Viewed from above, Epacmus is an attractive, tapered, fuzzy insect about 7-10 millimeters in length, with delicate wings and something of a smiley-face pattern where the abdomen meets the thorax. Cute. Look at one directly from behind and you get an entirely different picture. Suddenly, you see the big black eyes of a jumping spider. Four black, polished, hemispherical bumps on the rear of the thorax are a perfect match for the eyes of a small salticid (jumping spider). This is reminiscent of raised features on the thorax of the Brazilian fruit fly Ceratitis alba (See Hill, David E., et al. 2019).

Habronattus sp. jumping spider stalking a Andrena sp. mining bee

Ok, so how often might the fly encounter a jumping spider? More frequently than you might imagine, even on flowers. Another photo I took of a mining bee revealed a jumping spider right on her tail. I hadn’t noticed the spider until I looked at the image later, at home. Habronattus jumping spiders are abundant in this prairie habitat, and hunt exactly where you expect to see bee flies: on the ground, vegetation close to the ground, and on flowers. The spiders are small and cryptic, easily overlooked.

Male Epacmus bee fly

What else are we missing in our observations of insects and their spider predators? Keep observing and you, too, may make a startling addition to our collective scientific knowledge.

Note: At least one world authority on bee flies (Bombyliidae) asserts that Epacmus may not be a valid genus, but a subset of the genus Aphoebantus instead.

Female Epacmus bee fly

Sources:Rota, Jadranka, and David L. Wagner. 2006. “Predator Mimicry: Metalmark Moths Mimic Their Jumping Spider Predators,” PlosOne.
Mather, Monica H. and Bernard D. Roitberg. 1987. “A Sheep in Wolf’s Clothing: Tephritid Flies Mimic Spider Predators,” Science 236: 308-310.
Hill, David E., A.P.C. Abhijith, and Joao P. Burini. 2019. “Do jumping spiders (Araneae: Salticidae) draw their own portraits?,”Peckhamia 179.1
Melander, Axel Leonard. 1950. “Aphoebantus and its Relatives Epacmus and Eucessia,” Annals Ent. Soc. Amer. 43(1): 1-45.
Hull, Frank M. 1973. Bee Flies of the World. Washington, DC: Smithsonian Institution Press. 687 pp.
Cole, Frank R. 1969. The Flies of Western North America. Berkeley: University of California Press. 693 pp.

Spider or fly?

The Problem With "Murder"....Anything

It is a source of personal frustration that this blog must constantly address sensationalized mainstream press accounts of various insects and arachnids billed as the next great menace. That is putting things politely, actually. Humans excel at one terrible thing: creating enemies where none exist, or none would exist, were it not for people themselves.

Asian Giant Hornet, Vespa mandarinia© Allan Smith-Pardo, USDA APHIS PPQBugwood.org

It is also deeply troubling that a story about “murder hornets” is achieving more prominence than a story about the murder of a black male by a Caucasian father and son. Both hornets, and people of various demographics, are victims of unrelenting violence that they do not deserve. This is not a political issue; it is a humanity issue of staggering proportions and devastating consequences.

The fact that I can speak more intelligently about social wasps than people of color is disgraceful. I have a better education in entomology than in human cultural and ethnic diversity. Where did I fail? How did I allow myself to become an unwitting accomplice to institutionalized racism? How can I continue to advocate for “bugs” while my fellow human beings are fearing for their lives?

I know where to get factual information about insects. It comes from scholars I trust, from scientific literature that is thankfully now more accessible to the public than ever (are you reading this, journalists?), and from my own educational experiences, in class and in the field. I make an effort to learn, to understand, to act in accordance with what I know to be true. Science is by no means static; it also adapts to new discoveries. That is how we are going to get treatments and, hopefully, a vaccine for COVID-19.

The Asian Giant Hornet, Vespa mandarinia, is a large social wasp native to Asia, but adaptable to similar climates elsewhere if given the chance. That is what happened in Nanaimo, British Columbia, Canada, when a nest was discovered and destroyed in September of 2019. A single deceased specimen was found in Blaine, Washington, USA, near the Canadian border, in December, 2019. Genetic analysis showed it was from a different origin than the colony from Nanaimo. End of story, to date.

Asian Giant Hornet, Vespa mandarinia© Washington State Department of AgricultureBugwood.org

Yes, Asian Giant Hornets can decimate hives of honey bees to procure food for their larvae in the form of bee larvae and pupae. The adult wasps will also eat honey to fuel their flight muscles. The marauding wasps can be kept from entering hives with the installation of queen excluder devices.

The root of the hornet problem, and indeed all invasive species issues lies with human enterprise, but that is not sexy enough for media corporations competing for clicks and re-tweets. Responsible journalism would highlight lax inspections of shipping containers at international ports. Honest and brave writers would dare to suggest that our global economy threatens to undermine some industries (apiculture in this case) and destroy native ecosystems through accidental and intentional importation of exotic species.

Likewise, our problems with race relations and other social and economic conditions exist in places we don’t want to look: inside our white privileged selves, our monochromatic neighborhoods, our segregated private schools….We must come to terms with that for the collective peace and advancement of our society.

Hornets are armed with heavy-duty jaws and, if female, a sting. They operate on instincts that, while surprisingly plastic, can be brutal in their execution. Human beings can be armed with any number of worse weapons, some capable of annihilating entire cities and more, but graced with minds that can overcome instinct. We can adapt much more easily than insects, or any other animal species, to crises and challenges simply by changing our minds.

We must admit to, and own, our biases, faults, mistaken notions in the face of facts, and work to change them. That is the only honorable and just course for our lives, alone and together. Seize the opportunity to reject conspiracy, irresponsibility, and lack of empathy. Be a hornet of a different stripe, a warrior of compassion.

What the Insects Have Taught Me

A scientific education teaches you not to be anthropomorphic: Do not assign human emotions and sentiments and purposefulness to non-human animals. Be dispassionate in your observations, take phenomena at face value. This is a tactic for eliminating bias, and is useful in proper documentation, but it can rob you of a more fulfilling experience of the natural world. Thankfully, there is room for both a distant and intimate approach, perhaps no better exemplified than by the work of The Bug Chicks. I can certainly appreciate the lessons the world of insects, spiders, and other arthropods have already taught me.

A female dance fly, Rhamphomyia longicauda, from Wisconsin

Beauty has infinite definitions. An organism that is “ugly” to one person is a magnificent example of adaptation to another human. Whether you believe in evolution or creationism, you should have reverence and respect for all of nature. Sure, there are animals I do not particularly like, but I recognize the importance of their roles. Most of my biases have been created by the media anyway, which is not the animal’s fault.

A female Eastern Dobsonfly, Corydalus cornutus, guarding her eggs in Kansas

Indeed, diversity is the very essence of life, the soul of the planet. It is the very foundation of ecosystems and biospheres. If you begin to undermine that, believe that our species can successfully “manage” nature without all the requisite parts, then you are on a slippery slope guaranteed to end in cataclysmic tragedy at some tipping point you did not see coming.

We are more rigid in our human ideologies than invertebrates are inflexible in their instincts.

Metamorphosis can be a metaphor, but a lot can go wrong. It can take longer than expected. It may require a period of diapause, emphasis on “pause.” Our personal evolution comes only through learning, expansion of our comfort zones, shedding of destructive habits, agreeing to the assumption of risk, and recognizing our personal responsibilities. Unlike insects, which undergo a segregated set of life stages, we frequently revert to old behaviors that we should have outgrown, or we fail to advance at all. We have to forgive ourselves, and each other, in those events. There is no arrival, no final destination that defines individual human success.

A tattered male Four-spotted Skimmer, Libellula quadrimaculata, in Wisconsin

Handicaps are not the same as limitations. A grasshopper’s missing leg barely slows it down. Tattered wings do not ground a butterfly. Resilience, persistence, and an indefatigable relentlessness is the character of most insects. We can learn a great deal from such examples, use them as inspiration for our own recovery from physical or emotional trauma.

Perhaps the most revealing and disappointing conclusion I have reached is this: We are more rigid in our human ideologies than invertebrates are inflexible in their instincts. There is no such thing as a dumb insect. Their ability to solve novel problems and bend their innate programming never ceases to amaze me. They make up for any perceived intellectual deficits through sharper use of their senses and reflexes. Meanwhile, we cling to outdated, self-limiting, negative, hateful, and oppressive social constructs that prevent positive growth in our societies and civilizations. In many ways, we are more “primitive” than those animals without backbones.

The small can triumph over the bully.

We have only to change our minds to accommodate challenges and overcome obstacles. Other animals cannot adapt as quickly because they are designed for specific niches and habitats, confined to certain foods, and/or otherwise limited by their physical bodies. Yes, evolution happens, but at a slower rate than our brains (should) work. This is why protecting biodiversity is so critical. Rapid change is something Homo sapiens can adapt to, but not every other species.

Deer fly, Chrysops sp. biting me in Wisconsin

We are exceptional at creating non-existent enemies we call “pests.” With the possible exception of lice and bed bugs, there is no such thing as a pest. It is a term we assign to any other species we perceive as a competitor for “our” resources. We must start recognizing resources as entities that are shared with other species, and alter our approach to their extraction, growth, use, and/or disposal. Nature always pairs scale with complexity. Vast habitats are complex. Monocultural agriculture is not. Tree farms are not the same as forests.

The most heartening lesson insects can teach us is that the small can triumph over the bully. You need only look at all of our failed efforts to eradicate mosquitoes, locusts, and other insects for inspiration in your own fight for justice, equality, and human rights. Our so-called minority populations, the underprivileged, the underserved, underemployed, and undervalued sectors of humanity will get their due. The sooner that happens, the better for all of us. The economy is just another ecosystem, built on diversity, that functions only when currency flows like energy to all its living parts.