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Norfolk Naturalist Year in Photos, (Dec 2022-Nov 2023)

Siederia walshella, on the Lynn Valley Trail, April 2023:

On a walk on the trail by my house, I spotted this tiny creature (about a cm long) climbing up the trunk of a tree. I’m not positive on the identification, but it’s based on iNaturalist’s auto-ID for my photo and seems to match from what I can tell. If the ID is correct, this tiny caterpillar was likely searching for lichen to eat.

Eastern Spotted Newt (Notophthalmus viridescens), in my Parents’ pond, April 2023:

For the past few years, my parents’ garden pond has been host to these amazing creatures. All amphibians impress with their transformation from aquatic to terrestrial life but the Eastern Spotted Newt outdoes this life cycle with some incredible twists and turns. Larval newts transform into terrestrial juveniles (known as “efts”) and leave the water behind, living in the leaf litter. While on land, the efts have a rough reddish brown skin which keeps moisture in. After two to seven years, the efts undergo another transformation, darkening in colour and gaining a raised tail fin which aids them as they return to the water as aquatic adults. The newt pictured above is in this final stage of life: an aquatic adult. This isn’t necessarily the end of the newt’s transformations however, since some newt adults leave the water and regain some of their terrestrial attributes (rougher dry skin, loss of tail fin) for hibernation on dry land (Harding and Mifsud 2017).

Greater Bee Fly (Bombylius sp.), Lynn Valley Trail, April 2023:

This fuzzy fly has special adaptations to gather sand in its abdomen which it coats its eggs with before launching the eggs into solitary wasp nests (dug in sand presumably) (Marshall 2012). The larvae hatch from the eggs and enter the nest chambers of their host before feeding on a single host larva each (making the Bee Flies parasitoids, consumers of a single prey item).

Canada Goose (Branta canadensis) Parent and Gosling, Grant Andersen Park, May 2023:

Canada Geese are both common and abundant so they usually don’t catch my eye, but I really liked how the gosling was in the exact same pose as its nearby parent in this photo.

Spotted Sandpiper (Actitis macularius), Grant Andersen Park, May 2023:

The picture is blurry because the action was taking place across some water from my camera lens, but this fascinating courtship display was happening right in the middle of Simcoe in Grant Andersen Park. These shorebirds performed their display a few times and then mated and dispersed.

Sandhill Crane (Grus canadensis) family, Long Point, May 2023:

Sandhill Cranes have captures my heart with their wild resonant calls and their impressive size. It was a special treat to watch this family of two parents and two young foraging at the edges of a marsh in Long Point.

Canada Warbler (Cardellina canadensis), Long Point Old Cut Birding Station, May 2023:

Canada Warblers migrate into Ontario to breed during May/June, creating nests near the ground on stumps or small mounds (Bezener 2016). Then in late summer/early Fall they set off again to leave the Canadian winter behind them. Like other Wood-Warblers (the Family Parulidae) they consume insects and spiders, taken from plants or the ground.

White-Tailed Deer (Odocoileus virginianus), Lynn Valley Trail, June 2023:

This deer was incredibly close to the trail, so I was able to capture its gaze among the purple wildflowers.

Velvet Ant (Timulla vagans), Backyard, July 2023:

Velvet Ants are not members of the ant superfamily (Formicoidea) but are instead solitary wasps (members of the family Mutillidae). Their larvae develop as parasitoids on the larvae of other wasps (in the case of Timulla vagans, their hosts are Crabronids and Eumenine wasps (Marshall 2023)). The males of Timulla vagans are winged unlike the ant-like females and will carry the wingless females in their mandibles during their mating flight (Waldren et al 2020).

Physocephala marginata, Backyard, July 2023:

Although this insect drinking nectar appears to be a wasp, it is actually a fly of the Family Conopidae. Female Physocephala marginata seek out their lookalikes (wasps and bees) at flowers. After apprehending a host wasp or bee, P. marginata uses its abdomen to insert an egg inside the host’s abdomen (Marshall 2012). The egg hatches inside and the larval Conopid consumes the host from the inside.

Tachinid Fly (Exorista sp.), Backyard, August 2023:

Tachinid Flies are yet another group of parasitoid insects. Stephen Marshall, in his giant book on flies had this to say about this huge family of flies: “The Tachinidae is in many ways the ultimate fly family. With almost 10,000 named species and thousands more awaiting description… exhibits an unparalleled variety of sizes, shapes and colors. The range of life history strategies is equally amazing, at least within the constraint that every know species in the group is a parasitoid that develops inside another insect… or related arthropod” (Marshall 2012, p 386). Hosts of this genus are caterpillars or sawfly larvae.

Brown Marmorated Stink Bug (Halyomorpha halys), Backyard, August 2023:

This species of Stink Bug is native to East Asia but was introduced to North America accidentally in the 1990s. As with many successful and widespread introduced species, the Brown Marmorated Stink Bug can feed on a wide diversity of plants and can be a serious pest of agriculture and gardens. The pictured insect is a nymph, not quite an adult because it is missing fully developed wings across its back.

Green Heron (Butorides virescens), Waterford Ponds, August 2023:

The above photo was actually taken by my wife on an outing to Waterford Ponds. She was quicker on the draw to find and focus on this beautiful bird amidst the morning mist and tangled reeds of its marshy habitat. I’ve written an article about these amazing birds because of a different close encounter I had, go here to learn more!

Common Whitetail Dragonfly (Plathemis lydia), Front of House, September 2023:

As I was entering my house, I was stopped by the sight of this wondrous insect framed perfectly on my siding beside my door. I carefully entered the house to retrieve my camera in order to get this picture. One of the first Dragonflies photographed at my house since I don’t have a backyard pond… yet. The Common Whitetail pictured is a male, distinguishable because it has the chalky white abdomen which it uses as a signal to chase other males off of its territory. Females of this species have multiple bands on their wings and a dark abdomen.

Double-crested Cormorant (Nannopterum auritum), Lynn River, September 2023:

When swimming in the water, a cormorant reminds me of a hook-billed loon or a merganser, but their especially long neck gives them away. Like loons and mergansers, cormorants are underwater divers, pursuing fish prey amid lakes and rivers. This one was foraging in the Lynn River right in the middle of Simcoe, and I was very excited to get a close look at its sleek profile as it dried off on the bank. You can’t see them in the photo, but it was amidst a crowd of Canada Geese.

Great Spangled Fritillary (Argynnis cybele), Backyard, September 2023:

I at first thought this large butterfly was a Monarch (Danaus plexippus) as it was nectaring among our milkweed patch, but I quickly realized it was a different species. After patrolling our garden, this fluttering visitor rested and spread its wings on our orange plastic picnic table where I snapped this picture. The caterpillars of this species make it through our winter, after hatching just before the cold arrives (Hall et al 2014).

Black Swallowtail Caterpillar (Papilio polyxenes), Backyard, September 2023:

These colourful caterpillars feed on plants in the Carrot family (Apiaceae), and there were several munching away on our garden carrots this year. My 3-year old son helped me demonstrate one of their defensive strategies for this photo. If provoked these conspicuous caterpillars unfold the orange organ featured here, named an osmeterium, which has a foul odor (I would describe it as old rotten cheese, it was surprisingly powerful for such a small creature) (Marshall 2006). If I were a caterpillar-foraging bird or mammal, I would avoid such smelly prey.

Virginia Giant Hover Fly (Milesia virginiensis), Backus Woods, September 2023:

As the name implies, this fly was large and conspicuous in a sunny clearing. The larvae of these large flower flies (Syrphidae) develop inside rotting trees, sometimes inside tree holes (Skevington and Locke 2019).

Shadow Darner (Aeshna umbrosa), Backus Woods, September 2023:

Darners are huge dragonflies (over 7 cm long), instantly noticeable when in flight but this one cooperated in staying still while I took its picture. The Shadow Darner is named after its habit of flying late in the day (even at dusk) and staying mostly in shade (Marshall 2006). This one was photographed in the afternoon.

Chinese Mantis (Tenodera sinensis), Backyard, September 2023:

There are no Mantids native to Ontario, both of our common species: the European Mantis (Mantis religiosa) and the Chinese Mantis pictured here, were introduced to North America over a hundred years ago (Marshall 2006). This very large and impressive insect was clambering through my garden and nicely posed for a few pictures but this was my favourite photo I took, showcasing its powerful grasping forelegs and its triangular head.

References:

Bezener, Andy. 2016. Birds of Ontario. Partners and Lone Pine Publishing.

Hall, Peter, Jones, Colin, Guidotti, Antonia, and Hubley, Brad. 2014. The ROM Field Guide to Butterflies of Ontario. Royal Ontario Museum.

Harding, James H. and Mifsud, David A. 2017. Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press.

Marshall, Stephen. 2006. Insects: Their Natural History and Diversity. Firefly Books.

Marshall, Stephen. 2012. Flies: Their Natural History and Diversity. Firefly Books.

Marshall, Stephen. 2023. Hymenoptera: The Natural History and Diversity of Wasps, Bees, and Ants. Firefly Books.

Skevington, Jeffrey H. and Locke, Michelle M. 2019. Field Guide to the Flower Flies of Northeastern North America. Princeton University Press.

Waldren GC, Roberts JD, Pitts JP (2020) Phoretic copulation in the velvet ant Sphaeropthalma pensylvanica (Lepeletier) (Hymenoptera, Mutillidae): A novel behavior for Sphaeropthalminae with a synthesis of mating strategies in Mutillidae. Journal of Hymenoptera Research 78: 69-89. https://doi.org/10.3897/jhr.78.55762

For last year’s photo recap, see: Norfolk Naturalist Year in Photos (Dec 2021-Nov 2022)

Categories
diptera Species Profile

Callopistromyia, the Peacock Flies

For this article I’d like to consider one of the most beautiful insects I’ve ever had the pleasure of observing: the Peacock Fly (Callopistromyia annulipes) and its relative, the only other member of its genus the Peahen Fly (Callopistromyia strigula)*. The main difference in appearance between these two species is in their wings: C. strigula contains much narrower wings than C. annulipes (Kameneva and Korneyev 2006).

*There is no common name for C. strigula, so I made one up. You might be surprised that there isn’t a common name, but consider that there are hundreds of thousands of species of Flies, and many of these are only known within specialist groups that study the differences between them. This is also the reason that there isn’t much information available for these Flies despite their beauty and conspicuousness.

Callopistromyia annulipes, the Peacock Fly. Note the wide wings and the position they are held in above the body.
Callopistromyia strigula, the Peahen Fly. Note the relatively narrow wings, and their position held out to the sides of the body.

C. annulipes is distributed across the United States and occurs in three provinces of Canada: British Columbia, Alberta, and Ontario, while C. strigula is found in Manitoba, Ontario and Saskatchewan as well as several States. Over the past several years, this species has spread into Europe as well, no doubt via human means (Pintilioaie and Manci 2020). 

In both species males and females display, contrasting with many fly species in which only the males display for the females to choose from among them. I don’t want to discuss sexual selection and mate choice here in any depth. Suffice to say that because both males and females perform displays there is likely mutual sexual selection going on in these species, meaning that traits are preferred and chosen by both sexes in this species, rather than a female-choice bias or male-choice bias.*

*of course, this only applies if the displays and accompanying appearances are sexually selected for, but there are other ideas for what forces are selecting these displays (see further below).

Video of Peacock Fly (Callopistromyia annulipes) displaying on a bridge railing on the Lynn Valley trail in Simcoe.

Little is known of these species’ biology other than that they display on conspicuous surfaces (more on this below), and there are records of the adults of C. annulipes feeding on the frass from wood-feeding beetle tunnels* (Steyskal 1979). Their puparia** have been found beneath the bark of various deciduous trees, so it’s presumed that their larvae feed on dead wood, or fungi within dead wood or something associated with dead wood. 

*Frass is a fancy way of saying “insect excrement and related material” usually used in connection with wood-boring insects… that ‘related material’ bit is key here since although a lot of what we call frass passes through an insect’s digestive system it can also be broken up bits moved behind a wood-boring beetle, so less insect “poop” and more insect “debris”.

**puparia refers to the hardened larval skin that encloses the pupal stage of derived Diptera… which probably doesn’t explain very much unless you know what those other terms mean. Basically, instead of nothing surrounding the pupa (the transformative stage of insects, between larva and adult), a huge branch of the Fly Family Tree (the Cyclorrapha) hardens their final larval stage skin into a protective case, sort of the fly version of a chrysalis.

As with many Diptera, their larvae are mysterious. After much searching, I managed to find a few pictures of Callopistromyia larvae online. I was amazed and contacted the person who recorded these organisms to obtain permission to share the relevant information and images.

The pictures depict larval and pupal C. strigula which were found feeding on the inner bark of a boxelder tree (Acer negundo) (van der Linden 2018). I can’t find any pictures or information pertaining to C. annulipes larvae, but presumably they have the same or similar feeding habits. 

Finally, the most attractive thing about these species are their displays. The reason I’m writing about these flies is because I noticed them, and the reason I noticed them is because they strutted about on the railings of bridges on the Lynn Valley Trail. The Peacock Fly (Callopistromyia annulipes) in particular raises its large wings so that they meet above its back presenting a very noticeable display. By contrast, C. strigula adults display their wings in a more horizontal fashion. Presumably, these displays are about attracting mates and because the displays are performed by both sexes, they are about mutual mate choice. In other words, males are displaying to attract the attention of females and females are displaying to attract the attention of males. An intriguing possibility is that these wing displays are about more than finding a mate… they could also be an example of predator mimicry.

Can you see the face of a Jumping Spider in the Peacock fly’s wing-pattern?

A fascinating paper with an excellent title* describes how other species of Ulidiidae (the family of Flies that includes Callopistromyia) have wing patterns and displays that mimic the appearance of Jumping Spiders (Salticidae) (Hill et. al. 2019). The reason? Jumping Spiders are visually hunting predators of basically any insect they can catch. The wing patterns are possibly exploiting the visual system of Jumping Spiders by causing the spiders to believe they are staring down another Jumping Spider and so to be cautious. I can’t help but be intrigued by this idea, and somewhat skeptical. Despite its appeal, there are some problems with the hypothesis. One problem that came to my mind is that Jumping Spiders will hunt other Jumping Spiders. So if the pattern is supposed to resemble a Jumping Spider and deter them from predating the fly, why would it? The paper acknowledges that there are still many unknowns, but the authors make a good case that at least some insects are manipulating salticid responses to prey with visually deterrent patterns. And they also note: “In a natural setting even a brief delay in the attack of a salticid could allow these flies to escape” (Hill et. al. 2019). As always in science, more studies are needed…

*The title, for those of you who don’t read through the References section, is “Do jumping spiders (Araneae: Salticidae) draw their own portraits?” The idea is that in avoiding hunting insects that resemble themselves, jumping spiders leave those ones alive to reproduce in like kind and so jumping spider resemblances are crafted by the natural selection of the jumping spiders themselves.

There is always more to learn, and always new organisms to explore in the world. I hope you enjoyed my dive into the beautiful flies of the genus Callopistromyia, the Peacock Flies. 

References:

Hill, David, A. P. C., Abhijith, and Burini, Joao. 2019. “Do jumping spiders (Araneae: Salticidae) draw their own portraits?” Peckhamia 179.1: 1-14. (full pdf available here: https://peckhamia.com/peckhamia/PECKHAMIA_179.1.pdf)

Kameneva, Elena and Korneyev, Valery. 2006. “Myennidini, a New Tribe of the Subfamily Otitinae (Diptera: Ulidiidae), with Discussion of the Suprageneric Classification of the Family”. Israel Journal of Entomology. Vol. 35-36, 2005/6: 497-586.

Pintilioaie A-M, Manci C-O (2020) First record of the peacock fly Callopistromyia annulipes (Diptera: Ulidiidae) in Romania. Travaux du Muséum National d’Histoire Naturelle “Grigore Antipa” 63(1): 87-91. https://doi.org/10.3897/travaux.63.e50920

Steyskal, George C. 1979. “Biological, Anatomical, and Distributional Notes on the Genus Callopistromyia Hendel (Diptera: Otitidae)”. Proceedings of the Entomological Society of Washington. 81(3): 450-455.

van der Linden, John. 2018. https://bugguide.net/node/view/1510354

For other blogposts focused on Flies (the vast insect Order Diptera), see:

–5. Robber Fly Hunting Queen Ant

–Flies: The Natural History and Diversity of Diptera, by Stephen A. Marshall

–Flies Falling to Fungi and Other Dipteran Observations

–Fuzzy Flies and Song Sparrows

–Eastern Band-winged Hover Fly

Categories
book review

Flies: The Natural History and Diversity of Diptera, by Stephen A. Marshall

People are always going on about how Beetles are so diverse, biologists are always explaining to theologians that God must really love Beetles*, and whenever anyone asks “What’s the most diverse group of organisms?” Beetles are always top of the list. UNTIL NOW.

*in case you don’t know the anecdote this is referring to, the earliest source (according to quoteinvestigator.com) runs thus: “There is a story, possibly apocryphal, of the distinguished British biologist, J. B. S. Haldane, who found himself in the company of a group of theologians. On being asked what one could conclude as to the nature of the Creator from a study of his creation, Haldane is said to have answered, “An inordinate fondness for beetles.”” (Hutchinson 1959).

Stephen Marshall proposes in his magnificent volume on the diversity of flies that there are historical reasons why beetles are held up as so diverse when the truth is that they might just be more closely studied than other insect groups… other groups like the order Diptera (true Flies), for instance. And if you read through this 600 page volume loaded with superb photographs and covering every single family of flies in some detail you will come away with the powerful impression that Stephen Marshall is on to something. Flies, a group often neglected because they don’t always photograph well, many look very similar to each other, and a lot of them have distasteful feeding habits, are showcased as the hyper-diverse evolutionary marvel that they are.

Metallic Green Long-legged Fly (Condylostylus sp.), photographed in my backyard, June 2018. I’m just going to post some of the many interesting flies that I’ve photographed myself throughout this article. Stephen Marshall mentions that digital photography is opening up the realms of entomology to amateurs in a way that hadn’t been possible in the past. I wholeheartedly agree!

The book’s first part: “Life Histories, Habits and Habitats of Flies” runs through a sampler of what flies do as larvae and adults. This includes the life cycles of Diptera in general, but elaborates on more specific groups where appropriate. Other sections in this part describe flies interacting with plants, fungi, invertebrates and vertebrates. This entire section comprises about 90 pages and goes into considerable detail on specific guilds* such as the worldwide coastal communities of “wrack flies”, flies that have larvae that feed within decomposing piles of seaweed washed upon shores. Along with the various interactions between flies and invertebrates, this section also includes a discussion of the many human diseases caused or carried by flies such as mosquitoes (Family Culicidae) or house flies (Musca spp.).

*A guild is a group of animals that are united by a common feeding strategy or resource use, but not necessarily united in relatedness. For example, flies from different branches of the Dipteran family tree are considered part of the leaf-mining guild if their larvae produce mines in leaves.

Eutreta novaboracensis, a Fruit Fly of the family Tephritidae, photographed in my backyard, June 2018.

The second part of the book is titled “Diversity” and reading through this catalog of fly families and subfamilies truly does drive home just how incredibly diverse the Order Diptera is. Each chapter covers a large portion of the fly family tree and opens with a diagram of the proposed relationships between the fly groups within. This opening section of each chapter moves from family to family, and describes the basic characteristics of each group detailing subfamilies where possible as well. Within these descriptions are not just lists of characters used to distinguish one family from another but also the basic biology of each group when known. A couple of key things to note here: even when dividing up the flies into smaller and smaller groups it can be hard to generalize because you are still dealing with huge swaths of species in some instances and in others you are simply dealing with species doing very different things despite their close-relatedness. Marshall does a good job of explaining this and I’ll provide an example here from the section on Tipulidae (the Crane Flies, of which there are more than 15 000 described species): “Although most larvae with known biologies are saprophagous and eat microbe-rich organic matter (normally, decaying plant material) in wet environments, some crane flies are predaceous, fungivorous or phytophagous… Some groups have become specialists in extreme environments such as caves, marine intertidal zones and deserts, but most occur in humid forests and wetlands. Most Tipulidae are unknown as larvae.” (Marshall 2012 p. 110).

Crane Fly (Tipula sp.) photographed on the Lynn Valley Trail, May 2018.

The above quote demonstrates the way in which Marshall overviews the lifestyles of the fly groups providing tantalizing glimpses of their diverse life histories, but it also provides an example of something that is rife within the 600 page volume: the overwhelming amount of flies or fly habits that are unknown. To demonstrate, here are some quotes from throughout the book (Marshall 2012):

“Valeseguya rieki is known only from a single male specimen” (p 136)

“Larvae and larval habitats of the Lygistorrhinidae remain unknown” (p 141)

“Nothing is known of the biology of these obscure little flies [Ohakunea]” (p 141)

“adults of Oreoleptis (and thus the family Oreoleptidae) have yet to be collected in the field” (p 198)

“The 500 or so species of Acroceridae occur in every part of the world, but most are known from only a few specimens” (p 205)

“Essentially nothing is known about the biology of either Apystomyia or Hilarimorpha” (p 235).

“Even though signal flies [Platystomatidae] are usually conspicuous and attractive flies, many species remain undescribed.” (p 332).

“Larvae are unknown for most species in the family [Lonchaeidae] and little is known about behavior” (p 335).

“The biology of most Pallopteridae species remains unknown” (p 339).

“The truth, however, is that we know almost nothing about the life histories of these bizarre flies [Ctenostylidae]” (p 340)

“Nothing is known about the biology of this group [Nothybidae]” (p 348)

“Despite a worldwide distribution, with about 140 known species spread over every zoogeographic region, not much is known about asteiid biology.” (p 363)

“Nothing is known of the biology of the Neotropical dwarf fly genera [Periscelididae]” (p 365)

The quote list above is not comprehensive, but rather a sampling to show some of the many groups of flies that are mysterious despite their ubiquity in some cases. I don’t want the quotes above to be taken as evidence that the book contains little in the way of information on the flies of the world, seeing as so little is known overall. On the contrary, this volume is chock-full of biological details found nowhere else except the specialized literature and I found myself blown away by many intriguing and fascinating descriptions of fly families and subfamilies. Below are a few of the more interesting groups I had never encountered before reading through this book.

Frog midges (Corethrellidae) are attracted to singing frogs where the females feed on the frog’s blood. Some Phorid flies lay their eggs inside ants, where their larvae consume the ant’s head from the inside. After feeding within, the larvae decapitate the ants and pupate within the armored shelter before emerging as adult flies. These flies are known as ant-decapitating flies, and there are more than 300 species of them in the genus Apocephalus. Vermileonidae is a family of flies known as “wormlions” which are essentially the antlions of the diptera, their larvae constructing cone-shaped pits to trap wandering insects for prey. The Fergusoninidae is a family of flies that “develop only in galls induced by a specialized and codependent group of nematodes” (Marshall 2012, p 366).

Probably my personal favourite are the smoke flies. The smoke flies, platypezid Microsania spp., are attracted to fires (even campfires) but are rarely seen elsewhere. The smoke fly swarms are often followed by the predatory empidid dance fly Hormopeza which “seems to be a specialized predator of smoke flies. Like Microsania, the smoke dance flies are rarely seen except when they appear in plumes of smoke.” (p 298). I feel like the smoke flies, a group of species that can be attracted to something as common as a campfire, and yet are known from basically nowhere else (and thus poorly understood biologically) perfectly encapsulate the mystery and wonder of flies that I have gained from reading this book.

All of this fascinating information is found within the comprehensive and authoritative text, and after going through family by family in this fashion, each chapter in the “Diversity” section has a “photographic guide” portion which covers representatives of most subfamilies with further notes on natural history and significance of genera pictured. The scope of the pictures is mind-boggling and further bring home the diversity of flies, as well as their surprising beauty.

Transverse-banded Flower Fly (Eristalis transversa), photographed in my backyard, September 2018.

The final, shortest section covers collecting, preserving and identifying flies, and contains notes for those interested in starting insect collections of their own (as in, pinned specimens) as well as keys for identifying the major fly groups.

I can honestly say that if this book were published with only the text portions I would buy it because the text is just that valuable in overviewing the enormous diversity of the fly families. And I can also say that if this book were published with only the pictures and captions, I would also buy it for the incredible amount of biodiversity on display, captured in wonderful images of flies from around the world.

I cannot recommend this book highly enough. If you are an insect enthusiast, if you are at all interested in the diversity of life and if you enjoy gasping at revelations about the tiny wonders that flit around the world you have to read this book.

References:

Hutchinson, G. E. 1959. “Homage to Santa Rosalia or Why Are There So Many Kinds of Animals?” The American Naturalist, 93(870), 145–159. http://www.jstor.org/stable/2458768

Marshall, Stephen A. 2012. Flies: The Natural History and Diversity of Diptera.

For previous book reviews, see:

The Paleoartist’s Handbook, by Mark Witton

The Social Biology of Wasps, ed. by Kenneth Ross and Robert Matthews

Pterosaurs, by Mark Witton

Flora of Middle-Earth, by Walter Judd and Graham Judd

And for a podcast review, see:

The Field Guides

Categories
Species Profile

Eastern Band-winged Hover Fly

Ocyptamus fascipennis

Ocyptamus fascipennis adult, spotted at Algonquin Provincial Park, August 2019

When you’re interested in insects, you’re always going to be running into something new. There is always one more creature that you have never seen before, one more behaviour you haven’t heard of, and that’s because insects are incredibly diverse. Today, I’m going to pick out just one of the many species of insects to zoom in on, and explore its story.

The species I’ve chosen is Ocyptamus fascipennis, or the Eastern Band-winged Hover fly. Let’s start from the top: Ocyptamus fascipennis is a “True Fly”, a member of the Order Diptera, which is a division of the Class Insecta. Diptera means “two wings” which gives you the easiest way to identify this group of insects when you encounter them. Almost all insect groups have 4 wings (two pairs) but these pairs of wings have been modified into very different structures in different lineages of insects. For the True Flies, one pair of wings still provides lift and flight, while the other has been reduced into tiny knobs known as halters. These reduced wings act as stabilizers, giving the flies the ability to perform aerobatic feats of agility (as I’m sure we’re all familiar with in House Flies (Musca domestica)). The halters of Diptera are more than just balancing beams, they’re actually sending complicated signals to the fly about its aerial position.

Ocyptamus fascipennis is part of a Family of True Flies called Hover Flies, or Flower Flies (Family Syrphidae). The Syrphids are common insects in gardens where they feed on nectar and pollinate flowers. Because of this habit, many species of Syrphids have taken on the appearance of more conspicuous flower visitors such as bees and wasps, in order to gain some protection from the classic warning colours of black-and-yellow stripes. O. fascipennis in particular seems to mimic solitary wasps or types of parasitoid wasps with its elongated and narrow abdomen.

So far, we’ve been talking about adults of these flies, but all insects go through multiple life stages, some more dramatically varied than others. Diptera undergo holometabolous growth which is a fancy way of saying that they have life stages that look very different from each other and one of those stages is a transformation phase which is mostly immobile. When young hoverflies (larvae) hatch from eggs, they look very different from the adults landing and lifting from flower petals in gardens. Larval O. fascipennis have no wings, and no legs, and are sometimes known by the name that many fly larvae receive: maggots. O. fascipennis larvae don’t consume garbage or dead animals, but instead are active predators, squirming across leaves in search of their prey: aphids.

Stephen Marshall, in his incredible book about Insects describes Syrphine larvae hunting as this: “at night they move blindly among the aphids, grasping victims using typical maggot mouth hooks, then holding the doomed aphids up off the surface to consume the body contents.” (Marshall, 2006).

A Syrphine larva hunting a herd of aphids (photo credit: Christine Hanrahan)

It seems then that Flower Flies are very beneficial insects to have in the garden. They provide pollination for flowers, and their larvae consume plant-eaters such as aphids and related scale insects.

While I was unable to find very much information pertaining to Ocyptamus fascipennis specifically, one other member of the genus deserves special mention because of its interesting larval habitat: tank plants (Bromeliaceae). The Central American and South American species of Ocyptamus that inhabit these confined aquatic habitats (pools of water within the plant itself) ambush and consume other aquatic insect larvae that live in the plants alongside them. The larvae are even thought to use a paralyzing venom to subdue their prey (Rotheray et al, 2000).

All in all, Ocyptamus fascipennis and its relatives are fascinating flower flies with intriguing habits. I hope you’ve enjoyed taking a closer look at them today.

UPDATE NOVEMBER 2021: Near Point Pelee, Ontario, individuals of Ocyptamus fascipennis were observed apparently migrating. The flies were observed moving East to West along with several other insects including tens of thousands of potter wasps (Ancistrocerus adiabatus) (Skevington and Buck 2021). The authors of the paper note that insect migration is a largely understudied phenomenon, especially in North America, so further study is needed to figure out the details.

References:

Rotheray, G. E., M. Zumbado, E. G. Hancock and F. C. Thompson. 2000. “Remarkable aquatic predators in the genus Ocyptamus (Diptera, Syrphidae).” Studia Dipterolologica 7: 385-98. (full text available here: https://repository.si.edu/bitstream/handle/10088/17095/ent_FCT_89.pdf?sequence=1&isAllowed=y )

Marshall, Stephen. Insects: Their Natural History and Diversity. 2006.

Marshall, Stephen. Flies: The Natural History and Diversity of Diptera. 2010.

Skevington, Jeffrey H., and Buck, Matthias. 2021. “The first documented migration of a potter wasp, Ancistrocerus adiabatus (Hymenoptera: Vespidae: Eumeninae)”. Canadian Field-Naturalist 135 (2): 117-119.