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Invasion of the hover flies

According to several sources, Great Britain is being invaded by hordes of hover flies. We in the Pacific Northwest are seeing our fair share as well. So what is going on?

Hover flies are attracted to many of the same plant species as butterflies and bees, so it is no surprise that they are most abundant in the summer months. In addition, many of the hover fly species migrate as do some butterflies. In Great Britain, hover flies arrive in great quantities from southern Europe.

But the invasion of the hover flies is good news for gardeners since many of the larval forms eat yummy critters like aphids, thrips, and leafhoppers. Others eat decaying plants and animals. The adult forms of many species eat nectar and pollen and, in the process, become good pollinators.

Hover flies are so beneficial that many gardeners plant food plots especially designed to attract them to their patches. Among the plants most attractive are:

  • Agastache
  • Alyssum
  • Calendula (pot marigold)
  • Chamomile
  • Convolvulus minor
  • Coreopsis
  • Cosmos
  • Dill
  • Iberis umbellata (candytuft)
  • Lupine
  • Marigold
  • Oregano
  • Parsley
  • Queen Anne’s lace
  • Scabiosa
  • Statice
  • Yarrow
  • Zinnia

Unfortunately, hover flies, like many other invertebrate species, are losing valuable habitat to urban growth and modern farming. Although hover flies often go unnoticed, their ecological importance is significant—something that researchers are only beginning to piece together. Let’s provide them plenty of places to live . . . before they become endangered.

The poster below, prepared by Alvesgaspar and borrowed from Wikimedia Commons, shows a good sampling of the more common hover fly species.

Rusty

Hover flies. Wikimedia Commons photo by Alvesgaspar.

Comments

jess
Reply

since i am cultivating the world’s most prolific aphid population, i am fortunate to be hostess to a great number of hover flies right now. i try to console myself with bedtime stories of symbiotic balance et cetera, but it is a little painful. my poor brussels! the hover flies need to eat a little bit more.

jess
Reply

Maybe you can shed some light on this. I have 2 hives. I was looking at the entrance of the weaker hive, and I noticed a hover fly exploring around the entrance. It would go in for a few seconds, then come back out, then go back in, etc. The bees seemed to ignore it completely. Near the entrance of my stronger hive, I saw a hover fly eating a dead honey bee. Whether the hover fly was involved in the death or just scavenged the corpse, I am not sure. Once again, the bees seemed to be ignoring the hover fly completely. Have you seen anything like this behavior? Is the hover fly confused about its identity?

Rusty
Reply

I’ve never seen any hover flies around my hives. I could imagine the adult flies being attracted to the scent of honey from the hive, and that could be why one was investigating. But since adults are supposed to eat nectar and pollen–and not meat–I don’t know why the adult was playing with the corpse.

All that said, lots and lots of flies eat dead things. So maybe some hover flies eat dead things as well. Or maybe she was going to take it back to the kids for a snack, since the larvae eat meat. It’s hard to say.

As for why the honey bees didn’t seem to care, your guess is as good as mine. Maybe they don’t view hover flies as a threat. Once again, I’m clueless.

Asha
Reply

what is their threats???
(need it for school project)

Rusty
Reply

Asha,

Are you asking what threatens the hover flies? As far as I know, many birds do not prey on them because they are fooled into thinking they are bees. But hover flies are eaten by other invertebrates such as wasps and crap spiders.

beryl boote
Reply

Hi I have seen rather a lot of hoverflies, the ones that look like honey bees, and they seem to be coming in the house and dying. We have put three outside this morning, do you know the reason why? thanks

Rusty
Reply

Beryl,

I don’t know much about flies, but they don’t live very long. Perhaps it’s just their time.

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