Cluster Fly - Pollenia spp.When I first uploaded this drab looking specie of Fly to the blog last ye

Cluster Fly - Pollenia spp.

When I first uploaded this drab looking specie of Fly to the blog last year, I had only found one on the leaves. With a name like “Cluster Fly”, you would expect many individuals grouping closely together and hanging around to enjoy the warmth of a new spring. While I can honestly say that the Flies I found weren’t exactly super close to each other, the warm afternoon weather caused many individuals to come outside and swarm around. It was hard to get a moment’s peace outside with Fly after Fly landing on me or nearby and needing to be shooed away. It wasn’t quite a cloud, but there could’ve been at least 20 Flies nearby, and maybe more if some flew away and others took their place! If this is what they’re like outside, just imagine what happens when they hide away in confined spaces during the winter such as inside houses! Have no worries because as pesky as Cluster Flies sound, they only enter houses to escape the cold. When winter arrives, they enter diapause and await the end of winter to become active again: with their metabolism slowed down, they won’t breed. Even if they wanted to breed indoors, Clusters Flies seem to rely on parasitizing earthworms with their eggs. Maybe if have any potted indoor plants you might want to check the soil if you’ve seen adult Flies near them. 

A bigger problem that’s been reported with Cluster Flies is if they were to die indoors they may draw other predators indoors in search of an easy meal. Before searching your homes (inside and out) for a potential cluster invasion, remember that there are always signs you can watch for and ultimately they aren’t as big a pest as other types of Flies. They don’t tend to spread filth (beyond any germs in soil) and they feed on pollen from flowers rather than rotting material or garbage. I’d still recommend you wash your hands after handling them, and speaking of handling them, this is the first time I’ve ever stuck a finger out to a Fly and it actively climbed aboard. These insects aren’t skittish and react much slower compared to BlowfliesorHoverflies. While this makes me appreciative for the closer look at them, I do fear for their safety if they are sluggish aren’t predators. Perhaps the summer broods have more speed to spare, but if there is evidence to support that, I have yet to see it. If I find any answers, I’ll create a follow-up post, but these Flies tend to be overshadowed during the summer by the other flower-loving Fly species.

Pictures were taken on April 11, 2022 with a Google Pixel 4.