March Flies

Subject: New to gardening
Location: Royal Palm Beach, Fl
March 15, 2014 8:42 am
Starting a new garden about two weeks ago. Just planted some seeds and starter plants. Noticed last night that these little bugs were everywhere. I think they might be fungus gnats. Some were mating. Climbing mostly on the wood of my raised garden bed. What are they and how do I get ride of them if they are bad bugs?
Signature: Cheri

March Fly
March Fly

Hi Cheri,
We are nearly certain that both of the images you submitted are of March Flies in the family Bibionidae, and we are certain they are of different sexes, and they might be of different species.  First we will discuss the male March Fly.  His big head and larger eyes are typical of the sexual dimorphism or visual difference between the sexes that is typical of this family.  He looks like he might be Bibio albipennis, based on images posted to BugGuide, and BugGuide indicates it is:  “The most common and widespread species of
Bibio.”  The female with her smaller head appears to be a different species because of the black wings.  She might be Dilophus orbatus, which is pictured on BugGuide.  The family page on BugGuide indicates:  “larvae live gregariously in the top layers of soil and leaf litter, rotten wood, and dung; adults often found on flowers” and “larvae feed on leaf and needle litter, decaying organic matter, also on subterranean structures of live plants.”  If you started your garden with rich compost, that might explain the large numbers of March Flies that are appearing in your garden.  BugGuide also notes:  “Adults emerge synchronously in huge numbers and often form dense mating aggregations. Males form loose “swarms” and copulate immediately with females as they emerge from the soil. After mating, female bibionines dig a small chamber in the soil with their fossorial fore tibiae, lay eggs, and die within the chamber (Plecia lay eggs on the soil surface). Adults are short-lived (3-7 days).”

Female March Fly
Female March Fly


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