Toxonevra jucunda flutter fly.
At the risk of repeating myself, this week’s crawly is another rare one!
This is to be expected as we are in our twelfth year of Crawlies, and we’ve gotten to know many of our more common critters!
This week you’ll be happy to know there truly is a fly with the fun moniker of “Flutter Fly.”
Meet the Toxonevra jucunda flutter fly. They are in the Family Pallopteridae and are also known as flutter-winged flies, trembling-winged flies and waving-winged flies.
You may have already guessed this family of flies likes to show off those nifty wing patterns by holding their wings up and waiving them up and down rhythmically like little signal flags on a post.
If this seems familiar, there are other fly species with similar pretty patterns and behavior such as picture-winged flies (Family Ulidiidae) and signal flies (Family Platystomatidae).
Even though all these fancy, stained-glass-like winged flies are pretty amazing and fun to see, it’s the rarity of flutter flies which makes them extra special (as well as at least one other bonus we’ll get to).
There are about 140 species of picture-winged flies in North America and 41 species of signal flies. Meanwhile there are a mere 9 species of flutter flies!
But wait! There’s…less!
There are only six recorded sightings of flutter flies in Oregon on BugGuide with a few more on iNat – a “whopping” 10 recordings.
To be fair, it can be quite difficult to separate out flutter flies from signal-winged or painted-winged flies or even from some species of marsh fly (Family Sciomyzidae) and fancy fruit flies (Family Tephritidae) – there are a lot of very lovely fancy-winged flies out there!
The ID difficulty may account for some of the shortage of flutter fly sightings, but overall scarcity in the West is the largest factor. Of the just over 1,000 sightings of flutter flies on iNat nearly all of them are east of the Mississippi River.
Here on the West Coast, and especially in Oregon the best we can do is hope we get a lot more of them.
Why?
It turns out flutter fly babies (larvae) have quite a beneficial diet. Beneficial to them because it helps them grow and beneficial to humans (and every other critter living in the PNW forests!) because they are free pest control.
One of the main dishes for bitty baby flutter flies are the larvae of longhorn and bark beetle larvae (Cerambycidae, Curculionidae: Scolytinae). How cool is that?!
Some may feed on fungal mycelium under maple bark in the absence of beetle larvae, and that’s beneficial too. We certainly have lots of maple trees for them to live on and clean up.
Adult flutter flies feed on nectar, pollinating as they go. Not only are they very pretty flies, but pretty dang nifty to have around.
Along with our pictured jucunda we have at least three other species of flutter flies here in Oregon.
Because of the overall scarcity of flutter flies they haven’t been studied as much as we’d like them to be. We do know they are teeny, about one-eighth of an inch, and that jucunda live in boreal forests from Colorado west and north, and that females lay their eggs on the food source plant (so any tree with bark beetle larvae, or a maple with fungus).
Flutter flies are frequently found in shady areas in wetlands, and we have plenty of that type of habitat here in our area.
Final fun fact: Our featured flutter’s Genus name “Toxonerva” means “bow vein” for the bow (as in bow and arrow) shaped border on their wings. Their species name “jucunda” means “pleasing” and aren’t they just!