Two Flower Flies

by Carl Strang

Fresh eyes are a huge help in preserve monitoring. I always benefit when others join my exploratory walks at Mayslake Forest Preserve. Now I have it even better, as a second naturalist now has an office at Mayslake. Nikki Dahlen has a special enthusiasm for arthropods, and the first fruits of her presence are the topic of this post. I had noticed that plenty of flower flies have been active on the preserve in recent days, but when Nikki made mention of them, I was encouraged to take a closer look. They turned out to be almost entirely in two groups, which for now I am assuming are two species. Photos were enough to identify the genera of both, and the probable species of one.

The longitudinal stripes on the thorax, yellow cross bars on the abdomen, and a peculiarity of wing venation, place this fly in genus Helophilus, but I don’t know which species.

Obviously a bee mimic, as was the case in the narcissus bulb flower fly I featured earlier in the season. The other abundant species of recent days meets the criteria for Eristalis dimidiata.

Different in color, but similar in general body shape and size to the Helophilus, Eristalis also loves flowers. Notice all the pollen stuck to it.

I look forward to additional insights from Nikki, and to seeing if these two flower flies are equally abundant in future autumns.

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