Flies

Flies swarmed over my ornamental shrub and I was confused. One expects to see flies collecting around, well, around less desirable resting spots. I have dogs and chickens, so there were plenty of other, more odiferous opportunities, but the flies clearly were more interested in my shrub. What was going on? Let’s find out.

Brown spots (fly poop) on leaves

Crane flies, dragonflies, butterflies, fruit flies, whiteflies, hoverflies, you’ve heard plenty about these flying insects in the garden, but what about the lowly housefly? It turns out, houseflies (Musca domestica) are not necessarily the pests they have always been made out to be, not completely anyway.

True, nobody wants a fly landing on their food. There’s too many awful places they may have been. Those hairy legs of theirs may have been walking around in some nasty messes. You may be surprised to learn, however, that one of the most common places to find houseflies… is in the flowers of your garden.

Housefly (USDA) Public Domain

The nature of flies

Most flying insects have four wings. Flies only have two. True flies are all members of the Diptera family. Unlike busy bees and industrious ants, most fly species are lazy. They are mostly meat eaters. They also feed on manure, rotting stuff, and even open wounds. (Ew!) What you may not know is that flies also enjoy cleansing their palettes with a sip of nectar now and then. When flies land on a flower for a sweet sip, their hairy/spiky legs collect pollen. Most of them don’t eat the stuff, or hoard it, the way bees do. It just sticks to them. When they fly to their next sipping/resting spot, the pollen goes with them and often pollinates that flower. The process continues at a surprising rate. It ends up that flies are probably one of the first pollinators of flowering plants.

Bees vs. flies as pollinators

We all know about honey bees pollinating our crops: the bees go from flower to flower, collecting nectar and pollen and they transfer the pollen to other plants, leading to pollination, fertilization, and food for us. The problem with bees, as pollinators, is exactly that - they take the pollen with them. Eventually, there is no more pollen in a particular flower. That means bees can visit a flower and not pollinate it. Flies, on the other hand, generally do not eat pollen, so there is more left behind as they move from flower to flower, looking for a place to rest and have a drink. In a study conducted by the North Central Region Plant Introduction Station (NCRPIS), it was shown that adding blue bottle flies (Calliphora sp.), along with honey bees, as pollinators, carrot production was significantly increased. Also, flies are active within a wider temperature range than honeybees.

Crops commonly pollinated by flies

There are a surprising number of crops regularly pollinated by flies, besides members of the carrot family. These include apples, raspberries, strawberries, pear, plum, cherry, peach, nectarine, blackberries, and pawpaw. There is a group, called flower flies (Syrphidae), that pollinate dozens of our food crops. One particular species of fly, Ornidia obesa, is the reason we have chocolate. Yes, I said it. Flies pollinate cocoa plants.

Flies may not pollinate as many crops as bees, but they are already a close second, and that claim is made with only minimal research. We may find they are responsible for far more pollination. That being said, flies can also carry disease. They are free to roam my garden and landscape, but my patio is draped overhead with fly paper. Simple, yet effective.