Currently viewing the category: "Signal Flies"

Subject:  What type of fly is this?
Geographic location of the bug:  Brantford, Ontario
Date: 07/26/2019
Time: 11:26 AM EDT
Your letter to the bugman:  Hello Bugman,
I am hoping that you can help me identify this fly. I was leaning toward a type of syrphid fly but could not find a match online. Any help would be greatly appreciated.
How you want your letter signed:  Dan

Signal Fly (left) and Red Milkweed Beetle

Dear Dan,
The image of the Fly with the Red Milkweed Beetle is an easier image for identifying purposes as it clearly shows the wing pattern on this Signal Fly in the genus
Rivellia which we determined thanks to images posted to BugGuide where it states the habitat is “on foliage, feces.”  We tried to determine if there is a relationship between Signal Flies and milkweed, and we located this BugGuide image and this BugGuide image and on The Pathless Wood we found an image and this information:  ” I did come across this interesting fly in my search, however, and later determined it is some sort of Signal Fly, a member of the Genus Rivellia. These flies are often difficult to identify from photographs alone; they are quite small, and identification depends on the presence or absence of tiny hairs called setae on the dorsal thorax, as well as the colour pattern of the wings and legs. They get their name from their patterned wings, which they tend to wave around as if signalling other individuals. I didn’t see this behaviour as this individual rested on an unopened milkweed blossom, so I was immediately taken with the unique pattern of its otherwise clear wings.”   So, for some reason, Signal Flies are attracted to milkweed, but we are not certain why.  Are there soybean fields nearby?  Your individual reminds us quite a bit of the Soybean Nodule Fly, Rivellia quadrifasciata, which is also pictured on BugGuide.

Mating Signal Flies

Hi Daniel,
Thank you for this information. There was a soybean field right next to this patch of milkweed so I think it may be safe to say Rivellia quadrifasciata is a match. I’ve seen other flies exhibit this behaviour of waving their wings around. Now I know where to start when trying to identify them.
Thanks again!

Subject:  Possible fly species??
Geographic location of the bug:  Western Ohio, Youngstown area
Date: 07/05/2019
Time: 08:22 AM EDT
Your letter to the bugman:  We were on a truck delivery when we spotted this little guy on our side mirror. I never saw a bug like it before. He hung around, fended off a normal house fly, and was eating the dried bug guts off the mirror casing. No mandibles, one wing set. He was feisty. Lost him on our way to the next location. Got a good close-up of it eating.
How you want your letter signed:  Nadori

Signal Fly

Dear Nadori,
Isn’t Youngstown considered eastern Ohio?  This looks to us like a Signal Fly, possibly from the genus Rivellia based on this and other BugGuide images.  Of the family Platystomatidae BugGuide notes:  “Occur mostly in fields, some in woodlands.  Adults found on tree trunks and foliage; attracted to flowers, decaying fruit, excrement, sweat, and decomposing snails. Larvae found on fresh and decaying vegetation, carrion, human corpses, and root nodules.”

Subject:  Flies on Zululand coast
Geographic location of the bug:  South Africa, KwaZulu Natal, Mabibi
Date: 01/25/2019
Time: 03:25 PM EDT
Your letter to the bugman:  Flies on a tree in coastal Zululand. Mabibi.
How you want your letter signed:bewilderbeast

Buzzard Signal Flies

Dear bewilderbeast,
These are really crazy looking Flies, almost like toy flies.  This is only the second posting we have made in 17 years of the Buzzard Signal Fly,
Bromophila caffra, from South Africa.  According to WTB? contributor Piotr Naskrecki on his awesome blog The Smaller Majority where he uses the descriptive common name Red Headed Fly, they are:  “large, slow moving insects, reluctant to take to the air, and much happier to hang in clusters from low tree branches. They are truly striking animals, showy and clearly unconcerned about attracting anybody’s attention, including that of potential predators. …  But for an insect as conspicuous and common as the Red-headed fly, shockingly little is known about its biology. In fact, the last scientific paper that mentions it by name (according to an extensive MetaLib cross-database search) is from 1915, and it does so only to compare the fly’s strikingly red head to another species. As already pointed out in an excellent post about this species by Ted C. MacRae, there exists only anecdotal evidence that the larvae of this species might be feeding on the roots of Terminalia trees, potentially sequestering toxic cyclic triterpenes, which would explain the adult flies’ aposematic coloration. But, as is the case with so many African invertebrates, nobody really knows.”  A very detailed image of the Buzzard Signal Fly can be found on Encyclopedia of Life.

Buzzard Signal Fly

Subject: What bugs are these?
Location: Cairns, QLD, Australia
December 3, 2016 7:11 am
Found these in my yard.
Signature: CE

Signal Fly, we believe

Signal Fly, we believe

Dear CE,
We believe this is a Signal Fly in the family Platystomatidae based on this BugGuide image of a member of the genus
Rivellia.  According to BugGuide they are found:  “worldwide, incl. most of the Americas” and “Found on foliage, feces.”  Australian species are represented on FlickR and Discover Life.  Because we will be away from the office during the holidays, we will be postdating this submission to go live at the end of the month.

Subject: Fly identification
Location: Grand Police, Mahe, Seychelles
December 3, 2015 12:23 am
Hello! We are currently trying to identify present species within the wetlands on Mahe (Seychelles) and we found these flies on a palm leaf in the forest. Any idea what it could be? Your help will be greatly appreciated 🙂
Signature: Kristina

Fruit Flies

Signal Flies

Dear Kristina,
We are having a bit of a problem identifying your Fruit Flies beyond that we can state they are in the family Tephritidae.  Islands often present identification challenges because there is the possibility of endemic species that are not well documented, and there is also the strong possibility of introducing non-native species from distant locations.  Perhaps one of our readers will be able to provide insight into the actual species represented in your image.

Dear Daniel,
thank you for your reply! Even having the family helps us a lot. i am aware that islands to pose certain difficulties identifying species and especially here on Mahe there are a lot of introduced species some of which are morpholocilally quite similar to endemic ones.

Correction:  December 15, 2015
Thanks to a comment directing us to one of our own postings, we now agree that this is a Signal Fly in the family Platystomatidae, that is classified along with the Fruit Flies in the family Tephritidae in the superfamily Tephritoidea.  We stand corrected.

Subject: What’s this bug?
Location: South Africa
December 4, 2014 10:46 pm
On a recent trip to a game reserve in South Africa (Pilanesburg), we stopped at a picnic area and came across these weird looking “flies”. They where large, being approximately 2 cm long and there where about 20 of them in one concentrated area. They where very lethargic and did not fly off when approached or even moved with a stick. They move slowly.
Signature: Regards, Sean

Buzzard Signal Fly

Buzzard Signal Fly

Dear Sean,
To say that we were taken aback when we first viewed your images is an understatement.  We could not even decide if this was a wasp or a fly.  The general shape of the body indicated to us that it is a fly, yet the head almost looked more like a wasp.  To further complicate matters, our first stop for South African identifications, iSpot, is currently doing a site migration and though we found images that looked similar, we were unable to read about those sightings on iSpot.
  We eventually located a posting on FlickR that identified this unusual fly as a Rooikopvlieg, Bromophila caffra.



Searching that scientific name lead us to Beetles in the Bush where a lengthy posting provided a common name of Buzzard Signal Fly.  According to Beetles in the Bush:  “It is a member of the family Platystomatidae, commonly known as signal flies and part of the great superfamily Tephritoidea of fruit fly fame (i.e., true fruit flies – not “the” fruit fly which belongs to the family Drosophilidae and which are more properly called vinegar flies). … But what about Bromophila caffra? Aside from being one of the most recognizable of flies in Africa, it’s sluggish disposition and apparent noxiousness were obvious even to early naturalists. Marshall (1902) noted the similarity of its coloration (black body, blue wings, red or yellow head) to that of two Pompilus spp. and one sphecid wasp with which it occurred sympatrically.”    In closing, Beetles in the Bush coins a heretofore lacking common name with this justification:  “I find it surprising that a large, strikingly distinctive, abundant insect such as Bromophila caffra should lack a common name, but it appears this is the case. None was given in Field Guide to Insects of South Africa, nor amongst the several South African wildlife and dipteran websites which I encountered featuring photos of this insect. In thinking about what common name Bromophila caffra could have, I can’t help but draw comparisons between this insect and the turkey vulture (Cathartes aura), or “buzzard,” of North America (despite their belonging to entirely separate phyla). Both species are among the larger members of their respective orders and make their living eating repulsive foodstuffs. Hulking black with naked, red, plastic-like heads, most predators regard them as too vile and noxious to bother with, leaving them free to pass their lives in unmolested disdain. With this in mind, I hereby propose ‘buzzard signal fly’ as the official common name for this insect.”

Buzzard Signal Fly

Buzzard Signal Fly