In my mind, the word “flies” has been synonymous with “SWAT!, SWAT! & RE-SWAT!” No thinking, no hesitation, just get rid of them!
However, the object of my murderous intent, the common housefly (Musca domestica), is just one species of fly in the huge order Diptera. There are 120,000 known species and still counting. Literally thousands of these species have earned a much more benevolent response than instant smashing.
These Diptera species are the pollinators, performing a vital function for all of earth’s life. Among these essential tiny creatures are gnats, midges, no-see-ums, and, of course, a diverse assortment of flies.
As members of the Diptera order, pollinating families share certain defining characteristics including:
● Only one pair of functional wings (a few species are wingless);
● Halteres, a second pair of wing remnants. Dipterans use them as stabilizers or airspeed detectors;
● Large eyes;
● Life cycle is a complete metamorphosis; and
● Larvae have no true legs.
The relationship between pollinating flies and flowers is an ancient one, dating back at least 150 million years. Fossil evidence reveals that flies and beetles were the primary pollinators of the earliest flowers, instead of today’s hero, the bee. Bees simply had not evolved yet.
Flies visit more than 1,100 species of flowers and have the potential for pollinating each species at each visit. Flowers need efficient pollination, which requires a minimal loss of pollen and as little energy as possible spent on nectar production. Flies need nourishment, which involves finding the most nectar at each stop, simultaneously avoiding predators, watching for mates, and staying warm enough to fly.
Some pollinating fly species have evolved hairy bodies that much pollen can stick to at one stop and drop off at the next. In a reciprocating gesture, some flowers have even evolved ways to keep their insect guests warm.
A few of the best-known of our flying fertilizing friends are:
Hover Flies (also known as Syrphid Flies, Flower Flies & Drone Flies):
At 6,000 species worldwide, hover flies are by far the most numerous of the pollinating flies. Several species commonly occur in the Galveston-Houston region. In fact, an abundant population of hover flies typically exists from late spring to late fall in our area. However, they are not likely to be correctly recognized and oftentimes are misidentified as small wasps and bees. Most members of the family Syrphidae can fly like a helicopter, hovering and moving back and forth, side to side over flowers.
Size ranges from 4mm to 25mm. Colors range from drab gray or black to bright orange and yellow. Some species are confused with wasps and bees because their black and yellow abdomen mimics that of their more famous cousins.
In some agricultural systems, especially orchards, hover flies have been shown to out-do native bees in pollinating fruit such as apples, mangoes and peppers. Hover fly larva are second only to lady beetles and lacewings in their appetite for aphids, scales, thrips, and caterpillars.
Biting Midges and Gall Midges:
Species of no-see-ums from the Ceratopogomoidae and Cecidomyiidae families are the only known pollinators of cacao trees. The cacao bean is the foundation of that all-important food group, CHOCOLATE! For that, even I am willing to donate a little blood.
Yes, even these irritating little bloodsuckers have an up side. Actually, only female mosquitoes are of medical importance as male mosquitoes feed on flower nectar. Species from the genus Aedes pollinate Habenaria obtussta, an orchid found in the northwestern United States.
Lovebugs (also known as March Flies)
Come next spring, when you are scrubbing the gluey little black bodies of the Bibionidae family off your car to preserve the paint, just remember: the adult lovebugs are efficient pollinators. Also, their larvae hasten the recycling of organic matter.
Houseflies and Blowflies:
In one study of the pollinators found in Israeli mango orchards, blowflies were as important in pollination as the honey bee. The housefly still served as a pollinator, but was less effective.
It would be difficult to overestimate the significance of flies in their role as pollinators. So, for me, that means a revision of my SWAT & RE-SWAT philosophy: I will be far more discriminating before I smash!
Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.
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