This bee-mimicking fly caught my eye the other day because of the vertical lines on its thorax and horizontal lines on its abdomen. Looking for a Halloween costume? This fly is a referee on top and Waldo (from “Where’s Waldo?”) on the bottom.
The narrow-headed marsh fly or Helophilus fasciatus is a fairly large fly, about a half-inch long, and one of the earliest and the latest syrphid flies to be out and about each year.
What is this word, “syrphid,” you ask? It’s short for Syrphidae, a family of flies that imitate bees and wasps, and are important pollinators. Because they hang out around blooms, they’re also known as flower flies or hover flies. It’s a large group, with about 900 species known in North America.
The wetland part of the common name is interesting. Female narrow-headed marsh flies lay eggs on vegetation that overhangs ponds. The larvae are white, with long, rat-like tails, and they drop into the water and spend that part of the life cycle there, eating decaying vegetation. Helophilus is Greek for “marsh lover.” Fasciatus means “striped.”
I think this individual is female, because in most Helophilus species, they have four yellow abdominal stripes to the male’s three, and are somewhat leaner and longer.
See more of Karen’s work here.
Wikipedia has surprisingly extensive information: https://en.wikipedia.org/wiki/Helophilus_fasciatus. Accessed 10/18/23.
Link to a photo of a tailed larva: https://bugguide.net/node/view/1756696/bgimage. Accessed 10/18/23.