There is no way I can save this fly to post for Fantastic Fly Fridays, so I am improvising here and making a special DAY for a very cool fly. Marsh Fly Monday, it must be!
This is, as the title suggests, a Marsh Fly in the family Sciomyzidae (say “/sigh-oh-MIZ-ih-dee/”). The etymology of the name is from Greek skia meaning ‘shadow’ and myzo meaning ‘to suck.’ They are named so because the aquatic larvae of this group are parasitoids of snails, slugs, and fingernail clams. They are also referred to as Snail Killers. Some larvae are actually predatory and “hunt and kill” up to 30 snails before they reach their pupation stage of development. This particular species is Sepedon fuscipennis.
I observed this specimen for a few minutes in our unmowed yard. It’s got very cool, grasshopper-like hind legs, and weirdly, it moved (quite adeptly) backward when it was in the grass, before finally flying off.
From Cole, F. 1969Sepedon fuscipennis, From Cole, F. 1969
If you are curious to know more, check out the reference section below. Always be curious!
Bugguide. 2026. Sepedon fuscipennis. Bugguide.net. Iowa State University.
Cole. F. 1969. The Flies of Western North America. University of California Press Berkeley and Los Angeles.
ELBERG, KAUPO & ROZKOŠNÝ, RUDOLF & Knutson, Lloyd. (2009). A review of of the Holarctic Sepedon fuscipennis and S. spinipes groups with description of a new species (Diptera: Sciomyzidae). Zootaxa. 2288. 51-60. 10.11646/zootaxa.2288.1.3.
Peterson, M. 2018. Pacific Northwest Insects. Seattle Audubon Society.
Today, I am sharing photos I took yesterday of one of our PNW early spring pollinators. This interesting specimen is a male species of Dance fly in one of my favorite fly groups, the Empidoidea ( Dance Flies, Long-legged flies, and allies). It is in Genus Iteaphila. The name Iteaphila translates to “Willow lover” (from Greek ἰτέα, willow, and φιλία, love).
These small, blackish flies are quite frequently found in early spring visiting the flowers of willows, salmon berries, wild cherry, maples, and currants. My specimen was visiting the flowers of our yellow plum trees. Flies in this genus are exclusively anthophilous, feeding only on pollen (Sinclair & Shamshev, 2012). Others in the superfamily Empidoidea are predatory on smaller invertebrates.
The Iteaphildae have undergone some taxonomic revisions. Now, they include individuals with both branched and unbranched radial wing veins. On this specimen, I was able to discern the presence of a branched radial wing vein. There is also the distinguishing scutellar setae (seen in Figure D) in the diagram (Sinclair et al., 2023).
(Sinclair et al., 2023).Branched radial vein
Iteaphila flies are widespread across North America. The Genus ranges from Alaska and the Yukon, south to Baja, California in the West and from Northern Quebec to the southern Appalachian Mountains in the East.
Iteaphila sp. Dance Fly
I spent a fair amount of time reading over the literature I used in my references throughout the day when I could take a break. It’s getting late, and I’d hoped to have my post finished earlier. Working later in the evening is a mixed bag. It’s quiet and calm, but fatigue sets in and you can easily make a mistake. I may come back and revise this, but after going through the taxonomic keys by Anderson, I believe this is quite likely to be the species Iteaphila fuliginosa. Then again, I may end up corrected by someone more knowledgeable than me, or I may end up correcting myself. I’m 100% certain, I wouldn’t be the first to do this either.
From Anderson, 1973From Anderson, 1973
One might ask, “What is the value of a small, seemingly insignificant fly like this?” Aside from its role as an early spring pollinator, flies like this are part of the overarching food web. They provide nourishment for many organisms, ranging from other invertebrates (insects and spiders) to amphibians, reptiles, and baby birds. I would add that there is also value in the wonder of diversity in nature. It enriches our world. Hopefully we don’t take it for granted. It may be that a day comes along when it all disappears.
References
Anderson, D.R. 1973 A revision of the genus Iteaphila Zetterstedt of North America (Diptera: Empididae). MSc thesis, Utah State University, Logan, Utah, 59 pp.
Bugguide. 2026. Iteaphila. Bugguide.net. Iowa State University Department of Plant Pathology, Entomology, and Microbiology. https://www.bugguide.net/node/view/332912
Cole, F. 1969. The Flies of Western North America. University of California Press. Berkeley and Los Angeles.
Melander, A.L. (1946) The Nearctic species of Iteaphila and Apalocnemis. Bulletin of the Brooklyn Entomological Society, 51, 29–40.
Sinclair, B.J. & Shamshev, I.V. 2012. World revision of Iteaphila macquarti group (Diptera: Empididae). Zootaxa, 3561 (1), 1–61. https://doi.org/10.11646/zootaxa.3561.1.1
Sinclair BJ, Shamshev IV. 2021. World revision of Iteaphila with unbranched radial vein (Diptera: Empidoidea: Iteaphilidae). Zootaxa. May 7;4968(1):189. doi: 10.11646/zootaxa.4968.1.1. PMID: 34186945.
Sinclair, B.J., Brooks, S.E., and Cumming, J.M. 2023. An illustrated identification key to Nearctic genera of Empidoidea (exclusive of Dolichopodidae sensu stricto) (Diptera). Canadian Journal of Arthropod Identification. CJAI 48. doi:10.3752/cjai.2023.48 https://cjai.biologicalsurvey.ca/articles/sbc-48/
It was 51 and sunny to partly cloudy yesterday afternoon about 4pm when I meandered down to our unkempt orchard to look for pollinators. The temps had dropped the night before to around 34-35, so you could say it is still pretty chilly here in the PNW on San Juan Island. At least it is in our neck of the woods.
We have a couple of Yellow Plum trees in bloom. Don’t ask me the species. I don’t know. I might get ONE or TWO plums a year if I get lucky. It’s not for lack of fruit. It’s my lack of ambition or desire to go down and collect them all and I am NEVER EVER peeling plums again to make jam or anything like that ever again in my life. The time I did, it took my wrists months and months to recover. Also, I just don’t want to be a homesteader. Don’t get me wrong, I love living on 7 acres, but it is not because I can have a garden. It’s largely because I didn’t want to have close neighbors. I won’t get into that here, but let me tell you that 7 acres is nowhere near large enough. You need a hundred, and your house needs to be in the middle.
So, what flies do I have to show you today? There were four species I counted, maybe five, but the fifth one was so tiny, I didn’t work on any identification for that one. There was only one solitary bee. I’ll point out here that there were ZERO honey bees. #1, it’s too cold, and #2 because they can’t fly in temps over 50, they are not going to be the ones pollinating your fruit trees. It’s largely flies, moths, and maybe some ants and beetles. Mostly it is flies.
(Melanostoma mellinum) Variable Duskyface Fly
(Melanostoma mellinum) Variable Duskyface Fly
Fly #1 The Variable Duskyface Fly (Melanostoma mellinum). This is a species of Syrphid Fly and I believe my specimen to be male. Syrphid flies are wonderful in gardens and orchards. They not only pollinate, but they scavenge aphids away in their larval form. Watch this one in action here
(Melanostoma mellinum) Variable Duskyface Fly
Fly #2 The Cluster Fly (Pollenia sp.) Pollenia flies have had some taxonomic revisions that I am not completely up to speed with, but suffice to say that they are now in their own family (Pollenidae) and I’ll attach some references at the end if you want to deep dive into the literature and try and figure out the species here.
What I can tell you about these flies is they got their name because they will sometimes overwinter in human structures (clustering). They are an Old World group, so these are not native to North America. They are parasites of earthworms, or at least one of the species in the Genus is. They also were ALL over the plum tree. I bet I counted fifty of these.
Fly #3, I believe this one (below) is the Greater Spring Blacklet (Cheilosia grossa), a species of Hoverfly in the family Syrphidae. This species is native to Europe and was introduced to the United States as a biocontrol for thistles. The adult is obviously enjoying its role as a plum tree pollinator and its offspring (the larvae) will help manage the thistles on our property, I suppose.
Fly #4 is Empis barbatoides, a Dance Fly. I had to stand on my tippy toes to try and get this video clip for you. I love this species of fly. They are so cool. The males catch other fly species, like March flies (Bibionidae) and make little balloon packets to woo a female. If you don’t believe me, you can read one of my earlier blog posts about them. I know a spot where the males seem to gather together to dance too. I keep hoping I’ll get some good video of them dancing to share.
And that’s all for tonight. It’s late and I’m going to bed. Just remember to repeat to your friends that FLIES are your friendly pollinators, and some of them are pest predators too. We need more people to advocate for them. They aren’t always a pest! 🪰
References
Alcock , John. 1973. The mating behaviour of Empis barbatoides Melander and Empis poplitea Loew (Diptera: Empididae), Journal of Natural History, 7:4, 411-420, DOI: 10.1080/00222937300770301
Gisondi S, Rognes K, Badano D, Pape T, Cerretti P (2020) The world Polleniidae (Diptera, Oestroidea): key to genera and checklist of species. ZooKeys 971: 105-155. https://doi.org/10.3897/zookeys.971.51283
Jewiss-Gaines, A., Marshall, S.A., Whitworth, T.L. 2012. Cluster flies (Calliphoridae: Polleniinae: Pollenia) of North America. Canadian Journal of Arthropod Identification No. 19, 15 February 2012, available online at doi: 10.3752/cjai.2012.19
Aren’t we all? Hanging on for dear life? Whether it is financial, emotional, or health-related, it sure seems like folks in the world are facing a crisis of one sort or another. Some are facing outright catastrophic ones. We need a global re-set for the chaos. To calm my mind, I ponder bugs. How do you cope?
If you are just seeing my blog, it’s Fantasic Fly Friday. Flies are so varied and amazing. They literally fuel the world as we know it.
I photographed this one last night at my moth light. It was raining on San Juan Island, so there were more than a few bugs enjoying the refugia beneath our covered deck. Some nights it’s quite a party. A bug disco!
This is one of the more primitive flies in the family Trichoceridae (the Winter Gnats or Winter Crane Flies). Sometimes people call them hanging flies. I believe this one here is in the Genus Trichocera. However, I didn’t pluck my specimen off and take his or her life to determine that for certain under the microscope. I rather enjoy watching them alive because they all have quirky behaviors that are far more interesting to observe than counting wing veins on a dead bug.
The Trichoceridae are a family of Nematoceran flies grouped in the overarching infraorder Tipulomorpha (Crane Flies). There are approximately twenty-seven to thirty species of winter crane flies in the family Trichoceridae found in North America north of Mexico, depending on what source you use (Bugguide, 2021; Pratt, 2003). These are small to medium sized flies (wing up to 12mm), with a slender body and long, slender legs are distinguished from other families of crane flies by the presence of three ocelli (the primitive light detecting “eyes” found on the top of the head. Other identifying features include a V-shaped suture on the mesonotum that is incomplete in the middle, and long, hairlike 16-segmented antennae.
The larvae of Trichoceridae develop in moist or wet terrestrial biotopes. They can be found in decaying leaves, manure, fungi, stored roots/tubers, and rodent burrows (Bugguide, 2021). Adults are able to tolerate cool temperatures and sometimes, like I have seen, you may find them out walking on the surface in snow. Being active in winter, means there is little food available, but adults may feed on sap, or other carbohydrate sources. According to The Bug Lady (2015), they have been collected in molasses traps, and I have found them in our hummingbird feeder in winter when I take it down to change the sugar water and they are often on the sides of our seed and suet bird feeders as well. Perhaps taking nutrients in small amounts from the fruit in the bird feed mixes.
Winter Crane Fly in Snow, 2017 – San Juan Island, WA
Even though they are small (perhaps you have never even noticed them), these flies are significant in ecosystems, with the short-lived adults providing a winter protein source for birds and even bats. The larvae feed other organisms that go unseen in the winter (beetles, spiders, millipedes and such) that wake up hungry on warmer days. They are important decomposers, nutrient recyclers, and a wonderful bioindicator of ecosystem health. They do not bite, nor do they transmit disease.
Remember the behaviors I mentioned? Well, these flies dance like the world is ending. At least the males do. They can be find swarming on cool winter afternoons, bobbing up and down in what are known as ghosts (Burton-Hargreaves, 2026). Friendly ones! When I read that, it reminded me of a book by Robert Bright my mother read to me often as a child, Georgie and the Noisy Ghost. Just like the ghost in this childrens’ book, I find these little flies dancing about at my moth light to be delightful.
Winter Crane Flies may have a brief existence, but they make the most of it. We can too. Live in the moment. Read to your child. Be present and helpful. Check on your neighbor. Maybe Clang and Rattle a Bit about the state of our country to your representatives (in a polite email, of course). Stay connected, and hang on for the wild ride that is LIFE.
Pratt, Harry D. (2003). The winter crane flies of North America north of Mexico (Diptera: Trichoceridae). Proceedings of the Entomological Society of Washington, 105, 901–914. https://www.biodiversitylibrary.org/part/55628
Today I have a beautiful Fruit Fly (Genus Anastrepha) to show you. I found this specimen when visiting Tulum, Quintana Roo, MX in late January. The place we stay in Tulum has a swimming pool virtually no one ever uses. I love this place so much because I almost always have the pool entirely to myself. Everyone else is at the beach!
Anastrepha fruit fly
However, this particular pool is not maintained so well. More often than not, the filtration system isn’t turned on. I spend the first 15 minutes or so walking around in the pool to skim off all the bugs with a cup I bring from our room.
Unfortunately, my efforts to communicate, in broken Spanish, a request for a pool skimmer to the maintenance workers was a total failure. Probably they secretly referred to me as loco el bicho señora, or something like that. My Spanish is terrible. If you know me well though, finding bugs in the pool is literally one of the reasons I love staying at this place. I have my own vacay niche! Surveying for entomological diversity found in the pool.
There were more than a few bugs for me to “save,” that had landed on the water surface. Some, like this fly, had unfortunately already expired. I skimmed them all out, photographed them, then uploaded my observations onto iNaturalist. I even resuscitated a few that I thought were dead. Toilet paper or tissue paper “beds” work pretty well for drying them out in a pinch.
Fruit Fly (Anastrepha sp.)
I collected these photographs because I really appreciated the cool picture window patterns on the wings. This is one characteristic of fruit flies. This is also a female specimen as you can see from the longish posterior appendage, her oviscape. Last week, I tried to create a space away from social media to decompress, so I sketched her (to the best of my ability) and used my colored pencils to bring her to life. Probably I did not get all her bristles in the right places. On flies, bristles are diagnostically quite important. I’m not quite there with my artistic rendering, but it was a relaxing activity.
Fruit Fly (Anastrepha sp.)
In spite of their unique and beautiful wing patterns, fruit flies are often considered agricultural pests. Probably they wouldn’t be a pest except that we have these giant industrialized agricultural operations to feed more people than the planet should ever support, and probably, we artificially enable populations of various pests to explode because we are creating extra habitat for them. Fortunately, some targeted biocontrol and Sterile Insect Technique (SIT) has been effective enough to move producers away from utilizing harmful and unsustainable methods of chemical control, although I imagine some operations continue to apply pesticides.
This particular fruit fly is in the Genus Anastrepha. I haven’t really attempted going beyond genus level to identify this one to species. Anastrepha ludens, however, is a name that pops up often in literature from studies in Mexico and California. Anastrepha is a genus in the Family Tephritidae and I believe there are over 200 species of Anastrepha fruit flies in the Americas.
If you are interested in reading more about this genus, I would start off sending you to the 1963 study by Foote and Blanc, referenced below. I am currently waiting on a text I ordered from Abe Books on fruit flies, and will be doing additional reading once it arrives.
One interesting taxonomic tip I can leave you with: Tephritidae are true fruit flies. Those small flies that get into the bananas on your counter or into your rotting compost that many folks refer to as fruit flies aren’t fruit flies at all. They are vinegar or pomace flies, a completely different family called Drosophilidae.
Find out more when you follow me on Fantastic Fly Fridays!
References and Further Reading
Arias OR, Fariña NL, Lopes GN, Uramoto K, Zucchi RA. 2014. Fruit flies of the genus Anastrepha (Diptera: Tephritidae) from some localities of Paraguay: new records, checklist, and illustrated key. J Insect Sci. 1;14:224. doi: 10.1093/jisesa/ieu086. PMID: 25525098; PMCID: PMC5634125.
Greene C. T. 1934. . A revision of the genus Anastrepha based on a study of the wing and on the length of the ovipositor sheath. (Diptera: Tephritidae) . Proc. Entomol. Soc. Wash . 36 : 127 – 179 .
Here’s a unique specimen I have to show you. I found this fly on Wednesday after lunch when I went to look for a different species of fly around our above ground pool. I was actually looking for Woodpecker Flies when I found this one. Since I’ve committed to doing a presentation about them for the Scarab Society in September, I’m hoping to observe these weird Woodpecker flies again in the wild and take additional photos and videos to add to what I have collected already.
I didn’t expect to see anything IN the pool. Mostly, I was looking at vertical surfaces, like the sides of the pool and the sides of a nearby tree. When I glanced across the surface of the water, this little one stood out right away. I got a paper bowl to gently scoop it out, expecting it was deceased. It surprised me when it moved just a bit, then wiggled and flipped off the bowl onto the ground.
Chetostoma californicum
I bent down to inspect it, and when I touched it, it flipped around again like a fish out of water. Strange.
I had a plastic cup, so I managed to recapture the fly, wet and bedraggled as it was. I took it back into the house long enough for me to get my other camera. The lighting was better outside, so back out we went.
In case you are wondering, this is one of the Picture Wing Flies in the family Tephrididae. Also known as Fruit Flies. “Picture” references the patterned spots or stripes on the wings. There are other flies, like Drosophila sp., called fruit flies that aren’t actually fruit flies at all. THIS is a true fruit fly.
Many species of fruit flies are known for their pest status, however, there are over 4,300 described species in this family and the great majority of them are not pestiferous at all. They are merely a part of the local, natural ecosystem at large.
I used a key and geographic distribution records to determine the species for this one and believe it to be Chetostoma californicum. Trying to find host plant information led to me to do some deeper digging and to actually order a few more reference books on Tephridid flies. I have another fruit fly specimen I found when we were in Mexico, and plan to share that one with you next Friday. As I learn more about this particular one though, I will update my blog post accordingly.
The reference material I did find about Chetostoma californicum was largely from California and Arizona. Inferring from the documented host plant relationships recorded, it is likely one relationship possible in our immediate area is with native honeysuckle (Lonicera sp.). I also read adults of this species have been collected from Pines (Pinus sp.). We have a Pine tree just next to our above ground pool where the fly was collected.
Chetostoma californicum, identified by the oral edge of bucca (cheek) with a row of about 10 coarse, black bristles with a few finer black setae at the posterior end of the row. (LeBlanc, 1959)
The only additional personal record I have of this fly on San Juan Island is from February 16, 2024. I would conclude, based on my own observations, that this fly is not particularly an abundant species here. In checking for reports of the species on San Juan, my two posted observations are two of three total for the county.
Now if I can just find out what’s behind the fish flippy behavior…..stay tuned!
Chetostoma californicum (with pollen stuck to it after I accidentally dropped it into a Crocus flower)
Cole, F. 1969. The Flies of Western North America. University of California Press. Berkeley and Los Angeles.
Foote, R.H. and Blanc. F.L. 1963. The Fruit Flies or Tephritidae of California. Bulletin of the California Insect Survey. University of California Press. Berkeley and Los Angeles. https://essig.berkeley.edu/documents/cis/cis07.pdf
LeBlanc, 1959. A new species of Chaetostoma from California (Diptera: Tephritidae). Pan-Pacific Entomologist. 35:201-204. https://biostor.org/reference/225819
Wasbauer MS. 1972. An annotated host catalog of the fruit flies of America north of Mexico (Diptera: Tephritidae). Occas. Pap. Calif. Dep. Agric. Bur. Entomol. 19:1–172.
It has taken a bit of time to finally sort out genus and species for this very cool Robber fly with beautiful caramel-brown mottled wings I spied the evening of June 6, 2025. It perched on a dried apple mint stem from last season, no doubt scouting the terrain to see what might be on the menu for dinner. Robber flies (Family Asilidae) are predatory. They catch other small invertebrates to eat, paralyzing them with special salivary digestive enzymes and then sucking up the liquified contents through the proboscis (Cannings, 2013).
Getting to an identification beyond Genus for this one has been incredibly frustrating, and complicating the process is the limitation of the key I was using (Wilcox, 1946), which primarily describes male specimens.
Robert Cannings has studied the Asilidae for many years in British Columbia and states this genus “sorely requires systematic attention.” I finally just gave up and reached out to Rob for help. He wrote me and said, “I’m pretty sure this is Nicocles canadensis. It’s a female, and some females are difficult, even when under a scope, because the Wilcox key, which is the best we have for now, deals with them poorly and concentrates on males. Nicocles canadensis is the species in the genus most often seen on BC’s south coast and, I assume, in your area.”
This is the only Nicocles fly I’ve ever found on our property on San Juan. According to Rob’s 2014 publication (linked in the references below) in Canada, ” Nicocles canadensis is restricted to Garry oak savanna and adjacent dry woodland on southern Vancouver Island (Saanich is the type locality),” so I anticipate this may be similar for our neighboring area.
Check out the attached references if you are interested in learning more about Robber Flies in our region.
Cannings, R.A. 2013. Robber Flies (INSECTA: DIPTERA: ASILIDAE) Of The Montane Cordillera Ecozone.
Cannings, R.A. 1994. Robber Flies (Diptera: Asilidae) new to Canada, British Columbia, Yukon, and the Northwest Territories with notes on distribution and habitat. J. Entomol. Soc. British Columbia: 91: 19-26. https://www.biodiversitylibrary.org/part/213777
Cole, F. R. 1969. The Flies of Western North America. University of California Press. Berkeley and Los Angeles.
I thought I’d write up a short post about all the wonderful flies (and a few others) pollinating our plum trees in this cool spring weather. Why feature the flies? Well, for starters, the plum tree blossoms are white and flies love the color white. Another reason to feature the flies is because they are under-recognized and under appreciated, but very important pollinators. Some fly larvae even serve as pest predators, eating aphids. Others, like the tachinid fly below, use caterpillars that defoliate trees as hosts for their larvae to develop. Flies are also awesome because they do not sting! Some even “dance!” My favorite fly hasn’t shown up yet. It’s a Conopid Fly. More about that one later though…
Tachinid Fly (Epalpus signifier)
This past week in the media, there have been so many posts about the decline in honey bees. While there are some (unwanted) honey bees showing up on days when the temperatures climb above 50 degrees, honey bees aren’t active if it is cooler. Flies, on the other hand, are quite busy at work pollinating and do just fine when it might only be 40 outside. Flies are awesome! They need our support and appreciation.
I’d like to add (and I do know something about this because of my entomology background), that honey bees are just not necessary on San Juan Island. In fact, they might even be a very bad thing. They showed up at our plum tree as the temperature warmed up the other day, and as they arrived in increasing numbers, they kicked off ALL of the native pollinators that I had been observing. 😦
For honey bees to fly out of the hive and forage, they need temperatures above 50 degrees. In my experience keeping bees (as part of my graduate school work), they typically do not survive well on the island unless they are fed supplemental sugar water. Think about the ecological footprint of growing sugar to feed the bees!
Feeding honey bees attracts (and supports) the buildup of yellow jacket populations which are attracted to honey bee hive resources (including eating the honey bee brood developing in the hive), and honey bees also bring pests and pathogens that impact native bees (especially bumble bees). One more thing! If you are growing tomatoes, bumble bees are your pollinators, not honey bees.
I hope you will read and consider this recent study published about how honey bees were negatively impacting native pollinators on Giannutri Island in Italy. They were causing a decline in the populations of wild bees. In fact, the study cited an “alarming 80% decline in wild bee abundance over 4 years” (Pasquali et al. 2025). You can access this study to read it yourself here: https://www.cell.com/current-biology/pdfExtended/S0960-9822(25)00262-3
Enjoy the gallery of the native pollinators that I was fortunate to photograph and be able to share. Be a fly fan! Be a native bee fan! Learn about our unseen, but important night time pollinators (moths), and PLEASE LEAVE THE HONEY PIGS for the mainland industrial farm operations.
KEARNS, C. A. 2001. North American dipteran pollinators: assessing their value and conservation status. Conservation Ecology 5(1): 5. [online] URL: http://www.consecol.org/vol5/iss1/art5/
That’s right! Herman the Persian found something interesting in the yard when we were outside sunning ourselves a bit this afternoon. He found one of the Bibionid March flies (a female). If you read my post yesterday https://buggingyoufromsanjuanisland.com/2025/04/04/nuptial-gifts/, you might note that Bibionid flies were being hunted by Empis flies who rolled them into little balls as nuptial gifts used to woo the lady Empids to mate.
Female Bibionid fly digging chamber to lay her eggs.
Evidently, a few of these Bibionid flies escaped that destiny and actually mated with their own kind. THIS one, that Herman found, was hard at work digging her own death chamber where she would expire soon after laying her eggs. Incidentally, the adults are very short-lived, and in fact, live only about 5-7 days with the primary objective of mating, and for the adult female to lay her fertilized eggs. In spite of their brief existence, adults are also thought to be important early pollinators of orchard trees. Yes, you heard me right! Flies don’t get nearly as much credit for pollinating as they deserve to receive.
I watched her digging with her fossorial forelegs. It seemed to be an impossible task, but she made slow and steady progress. She was still hard at work before we went back into the house about half an hour later. I marked the spot with a rock so I could go back and check, but I suspect even with the rock nearby as a marker, it will be next to impossible to detect any disturbance in the soil tomorrow. We’re supposed to get rain this evening.
In approximately 30-35 days, the eggs she lays will hatch underground. The larvae will live in the top layer of soil and feed gregariously on leaf and needle litter, decaying organic matter, and sometimes on below-ground parts of plants.
If you’re curious, you can read more about Bibionid flies in the attached links. I did see some additional Empis fly males dancing about today with their Bibionid “balloons” or nuptial gift balls for prospective mates.
Morris, H. No date. The larval and pupal stages of the Bibionidae. Entomological Department, Institute of Plant Pathology, Rothamsted ExperimentalStation, Harpenden. https://core.ac.uk/download/pdf/212009582.pdf
This afternoon I would rate a 10/10 for entomological adventure. It happened outside, just behind our barn about 3:30pm. I went out to feed our resident raven and took a stroll over to a sunny corner of our property. As I neared an old barbed wire fence line, I noticed an aggregation of flies bobbing around over one of the native Ocean Spray (Holodiscus discolor) shrubs. Moving closer, as stealthily as possible, I saw these were Empis dance flies and I got very excited. There seemed to be about 15-20 in the group.
Empis Dance Fly (male) with Bibionid fly nuptial gift
I watched as I stood in the sun. The sun’s warmth felt really good on my body. Hopefully, we will have more sunshine and some days of vitamin D will infuse my cells and pull me out of this funk I have been wallowing in. The flies dancing in the sun were a sight. I crept forward a bit closer, trying not to slip into the fencing, but enough so as to get some video to share.
You will have to forgive me for the shake in the footage. It is not easy to remain steady and focus on a nervous fly that leaves its perch if you so much as breathe too deeply when you are moving the camera close enough to zoom in for a good macro shot. I think I was holding my breath a lot while I was trying to take pictures.
Empis Dance Fly with nuptial offering
This fly should be classified in the genus Empis. Last year, I found Empis barbatoides in our orchard. You can read an earlier blog post I wrote about them here https://buggingyoufromsanjuanisland.com/category/dance-fly/empis-barbatoides/ I believe these may be the same species, but I say this with a caveat. I am hoping to get my hands on a copy of the revisions by Sinclair, Brooks, and Cumming I have referenced below. It appears I may need this and the updated keys to try and ID my fly beyond genus level, so I’ve emailed the lead author and hopefully will hear something back.
If you look closely, you’ll see in some of the photos the fly is holding a balled up insect. This is a species of March fly in the family Bibionidae. I saw a few hiding around in the tall grass like this one in the photo below.
March fly (Bibionidae) hiding in the grass
Evidently, they were being picked out by the male flies and rolled up into a nice nuptial gift to present to a female Empis fly to entice her to mate. The male Empis fly will carry this balled up dead insect and “dance” around to attract a female. That’s what I found so fascinating to actually watch in person. It isn’t every day you see something like this! Since flies seem to be attracted to certain spots for mating aggregations (it’s called hilltopping), perhaps this is a spot where I might be lucky enough to see this action again.
References and Further Reading:
Alcock , John. 1973. The mating behaviour of Empis barbatoides Melander and Empis poplitea Loew (Diptera: Empididae), Journal of Natural History, 7:4, 411-420, DOI: 10.1080/00222937300770301
Sinclair BJ, Brooks SE, Cumming JM. Revision of the western Nearctic species of Empis subgenus Enoplempis (Diptera: Empididae). Zootaxa. 2025 Mar 31;5615(1):1-200. doi: 10.11646/zootaxa.5615.1.1. PMID: 40173481. https://pubmed.ncbi.nlm.nih.gov/40173481/
Bugging You From San Juan Island 