Yes, that is a fly, not a wasp. You can tell it’s a fly from the antennae in the center of the face, instead of the top of the head, the large, rounded eyes that cover both sides of the face, instead of being restricted to the upper part of the head, and the “forked” feet.
For comparison, here’s the all-black Sphex pensylvanicus, Great Black Wasp, to which Physocephala bears, I think, a superficial resemblance. Note the position of the antennae, the location, size and shape of the eyes, and the clawed feet.
Even before I knew what it was, from past experience, I knew that wing venation would be important in identification. By chilling this individual in the refrigerator overnight, I got a few minutes of close-focus macro time to highlight all the key features. Based on comparing the wing venation to other examples on BugGuide, I think this is Physocephala, but I’ve submitted it to their experts for positive ID.
Here are my other photos of this impressive mimic.
Trichopoda pennipes, Feather-legged Fly, on Pycnanthemum, Mountain-Mint, in my garden yesterday. Although it’s widespread and common, occurring throughout North America, this was the first time I’ve noticed this species in my garden. This photo shows several of the keys to identifying this species:
“Feathered” fringes on the hindlegs, true of Trichopoda.
Orange abdomen. Females have a black-tipped abdomen. Males, such as this one, have a completely orange abdomen.
Wings are completely black. This species has a transparent margin to the wing.
Trichopoda is a parasitoid of Hempitera, true bugs, including many agricultural and garden pests, such as squash bugs and stinkbugs. For this reason, it’s considered a “beneficial” insect:
Each female fly lays on average 100 eggs, which are placed singly on the body of a large nymph or adult bug. Most of the small, white or gray, oval eggs are placed on the underside of the thorax or abdomen, but they can occur on almost any part of the bug. Many eggs may be laid on the same host, but only one larva will survive in each bug. The young larva that hatches from the egg bores directly into the host body. The maggot feeds on the body fluids of the host for about two weeks, during which time it increases to a size almost equal to that of the body cavity of its host. When it has completed its development, the cream-colored third instar maggot emerges from the bug between the posterior abdominal segments. The bug dies after emergence of the fly, not from the parasitoid feeding, but from the mechanical injury to its body. The maggot pupates about an inch down in the soil in a dark reddish-brown puparium formed from the last larval skin, and an adult fly emerges about two weeks later. There can be three generations per year depending on location.
The fly overwinters as a second instar larva within the body of the overwintering host bug. Adult flies emerge in late spring or early summer. The only bugs large enough to parasitize at this time are overwintered adults. Subsequent generations develop on both nymphs and adults of the next generation. – Trichopodes pennipes, Parasitoid of True Bugs
One of the great pleasures of gardening is observing the activity the garden invites. I can lay out the welcome mat, and set the table, but the guests decide whether or not the invitation is enticing enough to stop by for a drink, a meal, or to raise a family. While charismatic megafauna such as birds and mammals are entertaining, the most common and endlessly diverse visitors are insects.
The Hymenoptera includes bees, wasps, and ants. Although my garden also provides amply for ants, we’ll stick with the bees and wasps today. Following are some of the few portaits I’ve been able to capture of the many visitors to my gardens. The pollinator magnet, Pycnanthemum, Mountain-mint, in the Lamiaceae, provides the stage for many of these photos. I’m always amazed at the variety and abundance of insect activity it attracts when blooming.
Multiple pollinators on Pycnanthemum
Bees
There are over 250 species of bees native to New York City alone. I’m still learning to identify just a handful of the dozens of species that frequent my garden.
My current favorite is the bejeweled Agapostemon, Jade Bee Bombus impatiens, Common Eastern Bumblebee, on Monarda fistulosa
Coelioxys, Cuckoo Bee. I think I’ve got several species from the genus visiting my garden, but I’ve yet to get identification for the others. These are in the Megachilidae, the Leaf-cutter and Mason Bee family. Bees in this family typically carry pollen on hairs beneath their abdomens, instead of in pollen baskets on their legs. You can see this bee isn’t carrying any pollen; it doesn’t even have the hairs beneath its abdomen to do so. It doesn’t need to, because it takes over the pollen-provisioned nests of other leaf-cutter bees for its own young.
Along with the Hymenoptera come the mimic flies. Many of the seeming bees and wasps, seen from a distance, turn out to be flies on closer inspection. In “the field,” i.e.: my garden, there are two features that provide quick distinction between the two familes:
Antennae: Flies have short, clublike antenna, like feelers, in the center of the face, between the eyes. Bees and wasps have long, segmented antenna arising higher up on the face, almost from the top of the head
Eyes: Flies’ compound eyes are huge, covering nearly all of their face. Bees and wasps have compound eyes that wrap partially along the sides of their heads.
The feet are also different, but I usually don’t notice those until I’m browsing and culling my shots. Finally, bees and wasps have four wings, while flies only have two – Di-ptera, two-winged.
The Syrphidae/Flower-Fly family hosts countless mimics of bees and wasps.
Eristalis arbustorum on Hydrangea
Eristalis transversa, Transverse Flower Fly
Their tactics of mimicry are not limited to patterns and colors. Many species have evolved body modifications to mimic even the shapes of wasps and bees.
Syritta pipiens provides a good example of this. This is the most wasp-like fly I’ve found yet in my garden, though more extreme mimics exist. Glimpsed from behind as it moves quickly over the flowers, it could easily be mistaken for a tiny wasp.
Viewed from the side, or the front, Syritta is more obviously a fly, not a wasp, and a dedicated mimic.
Toxomerus geminatus sports a radically flattened abdomen. This seems to be an adaptation to present a wider area from above, as a predator might view it, for displaying its mimicry, while preserving a smaller volume and keeping weight down.
I wonder what they are mimicing? Might some of these mimics mirror actual target species, not just general “bee-ness” or “wasp-ness”? If so, I would expect to find both the mimic and subject in the same range, and exhibit the same phenology. For example, Toxomerus bears a resemblance to Agapostemon at a quick glance.
Photographing Insect Activity
This is my setup for doing live insect macro photography “in the wild,” i.e.: in my garden. The lens is a specialized macro lens that allows for an extremely close focusing distance, though I’m not taking advantage of it in this example. I target some flowers with lots of insect activity, in this case, a local ecotype of Monarda fistulosa, in the Lamiaceae, the Mint Family. Then I wait for insects to visit the flowers, within range of the camera.
I use the tripod handle to pivot up and down; it turns side-to-side easily. Ease of rapid movement with stability is critical, as the insect subjects move rapidly over each inflorescence, and from bloom to bloom. Still, the tripod only steadies my own shaky hands. The insects, of course, are moving, but so are the plants, which sway with the slightest breezes. A fast auto-focus helps; a quick hand is still needed when automation fails.
The mobility allows me to track a single insect as it moves around, and capture different shots, and perspectives, on the same individual. This is critical for identification, since I don’t know until later what the key features to look for might be. It’s often some tiny detail, only revealed from some obscure angle, that distinguishes the species.
My subjects, while largely oblivious to my actions, are not cooperative. I have to shoot hundreds of photos to get a few good shots that are in focus, free of motion blur, and have enough of the right details to identify the species, or at least narrow down to the family. This was never possible, or at least not economically feasible, before digital photography.
Macro shot of Pycnanthemum inflorescences, with common objects for scale: left, pencil eraser, right, U.S. nickle coin.
Eric Grissell, Bees, Wasps, and Ants: The Indispensable Role of Hymenoptera in Gardens
Douglas W. Tallamy, Bringing Nature Home: How You Can Sustain Wildlife with Native Plants
The Xerces Society, Attracting Native Pollinators:Protecting North America’s Bees and Butterflies
Links
The bug geeks at BugGuide are awesome. Only through their generous sharing of knowledge and expertise have I been able to identify my little visitors. They cover the United States and Canada.
This beautiful creature is not a bee. It’s a fly of the Syrphidae, a family of flies renowned for bee mimics. This is Eristalis transversa, Transverse Flower Fly. I had noticed it in my garden for the first time this summer. yesterday was the first chance I had to capture some photos of it. Consider this a belated Garden Blogging Bloom Day post, but with a native pollinator as the focal point.
The flower it’s visiting is Aster novae-angliae ‘Chilly Winds’, a selection of the native New England Aster from Seneca Hills Perennials in upstate New York. This plant has been a pollinator magnet in my backyard native plant garden for weeks. It’s massive and overgrown and poorly placed, crowding out everything else around it. I’ll have to find it another place for next year.
