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Anita’s Blog – The Flies Have It

Updated: Dec 18, 2022


Black Bee Fly. (Photo by Anita Westervelt)

This post is about one tiny aspect of planting a garden, It’s about flies.


But first, winter is the best time to plant in the Valley, while temps are cooler and shrubs and trees and other plants won’t be stressed from drought and heat. As you plant or begin to design a garden, whether you want to attract birds, pollinators, bats, butterflies, moths or our friendly flies, plant a diversity of flowering species that bloom throughout the year. Think about planting to create mixed habitats and include decomposing materials like leaf litter or other organic matter.

To help with plant selection, a few notable publications are listed at the bottom of the list of local native plant growers at this link: https://www.stbctmn.org/post/valley-native-plant-growers-nurseries.


Consider plants with a variety of colors and shapes; plant in clumps and layers from low-growing perennials to vines, intermixed with flowering annuals.


Insects need shelter and overwintering habitats, like dense shrubbery, undisturbed soil areas, small piles of sticks and vegetative debris or a rotting log tucked under shrubs. Some flies act as scavengers, consuming rotting organic matter, like rubbish, garden waste and compost pile ingredients.


Learn more about our special and fascinating Valley habitat and the critters that depend on it through Texas Master Naturalist classes. Check out how to take the classes at this link and then come back and read all about flies in the rest of this post. https://www.stbctmn.org/the-next-class But hurry! Classes begin Jan 10th.


I was going to round out the year with twelve of my favorite bugs, but there were way more than twelve. Then I thought I’d showcase my 12 fav photos of 2022. Again – waaaaay too many.


Earlier this month, I Zoom-attended an Insect Appreciation Workshop that included a lecture about flies. Because of the nature of flies – flighty, skeptical and a bit paranoid – I’ve only managed to capture about dozen good shots of flies and that averages out to my year-end wrap-up.


There’s a lot more to flies than being the annoying pests at a summer barbeque, so let me say this right up front:

Those pestering common houseflies and bluebottles are important pollinators of crops,

like mango and avocado – so, step away from that fly swatter!


One of my most exciting finds during this year’s fall pollinator bioblitz was when I spotted black and white stripes in the innards of a rotting musk melon that had escaped the compost pile. It was a banded-wing fly, in the genus Chaetopsis and so tiny I’m amazed I saw it at all. There are more than 100 species in North America of these metallic-looking flies, considered picture-winged flies; their larvae feed on decaying organic materials, including rotting fruits.


Banded-wing Flies, Genus Chaetopsis. (Photo by Anita Westervelt)


Close up of the Banded-wing Fly (Photo by Anita Westervelt)

Flies live nearly everywhere on earth. There are more than 160,000 species of flies. They have interesting names, like hoverfly, soldier, black scavenger, root maggot, hairy-legged and sawfly.

The most interestingly named fly, which I found on the bathroom wall, was coincidentally named the bathroom moth fly, Clogmia albipunctata. These flies have a worldwide distribution in tropical areas and are found near sewer drains, sewage treatment plants, plant pots, swamps – basically near decaying, moist organic matter. The larvae have an important role in sewage treatment. The adults have weak flight, rest a lot, consume water and flower nectar and only live about 12 days.


Bathroom Moth Fly. (Photo by Anita Westervelt)

Although some flies are pollinators, they don’t get the big kudos like bees and butterflies. They might not be big and have splashy wing colors like butterflies and moths, but they do have some interesting and beautifully designed wings.

A few facts I learned during the Fly Lecture:

Flies cover more distance than bees.

Flies work in the rain.

Flies can remain active at low temperatures

Flies need energy and minerals which they get from nectar and pollen


Flies sip nectar and carry pollen from one flower to another, many fly species have evolved hairs on their bodies that pollen sticks to, but exchanging pollen is incidental. Some flies have specialized relationships with specific flowers, while other flies are generalists, feeding from a wide variety of flowers. Many flies are predators, feeding on insects such as aphids and others help to break down organic matter, which in turn, releases nutrients back into your garden.


Flies frequently hover in mid-air, like hummingbirds; they can move vertically and even fly backwards. Some flies enjoy a bit of mimicry fun looking like bees and wasps. To tell them apart, flies have large eyes, short antenna, three pair of legs at the thorax and one pair of wings, also at the thorax. Bees have two pairs of wings, one pair smaller than the other; most wasps also have two pairs of wings, one pair smaller.


Striped horse fly, Tabanus lineola. Several visited the black light/moth sheet during the summer. Most species of horse flies are multicolored with stripes on the abdomen and thorax. Both male and females feed on sugars for flight energy; males feed on pollen; females suck vertebrate blood for egg development. Horse flies usually bite cows and horses and can give humans a painful bite.


Flies have big eyes and short antennae like this Striped Horse Fly. (Photo by Anita Westervelt)

Striped horse fly. (Photo by Anita Westervelt)

Some flies are nutrient recyclers – this is a scientific definition by Wikipedia: “Nutrient recycling, or ecological recycling, is the movement and exchange of inorganic and organic matter back into the production of matter.” In other words, decomposers break down the organic matter that is present in dead and decaying plants and animals into inorganic nutrients, which can then be used by plants.


Flies are second in importance to bees as pollinating insects, according to a University of California Agriculture and Natural Resources blog, “The Pollen Nation.” In other countries, flies are essential for pollinating flowers of the cocoa tree. Other fruits and vegetables flies help pollinate include, pears, apples, strawberries, cherries, plums, apricots, peaches, rowanberries, raspberries, blackberries, roses, fennel, coriander, caraway, kitchen onions, parsley, carrots, and many more.


Hoverflies have developed yellow and black stripes on the abdomens, though they are not related to bees or wasps, it’s mimicry, perhaps a defense mechanism to deter predators – flies pretending to be stinging insects, though they cannot sting. Hoverflies are the most important fly pollinators. I photographed a margined calligrapher, Toxomerus marginatus, in mid-January on the petal of a plant. Calligrapher flies are bee mimics; they are a hoverfly and common in North America. Adults feed on flowers; larvae feed on plant pests like aphids, thrips, small caterpillars and other plant pests.


Margined Calligrapher Fly. (Photo by Anita Westervelt)

Poecilognathus unimaculatus is a genus of bee flies. Bee flies are bee mimics. They are extraordinary flyers that can hover in midair, move very fast and maneuver with great skill, changing directions in the blink of an eye, according to the U.S. Forest Service, U.S. Department of Agriculture. They have a stiff and long tongue (proboscis) and can probe into flowers to sip nectar while hovering in front of them. They still manage to carry and disperse pollen. It is thought that they avoid predators by not landing on the flower, predators like crab spiders and ambush bugs.


Poecilognathus unimaculatus. (Photo by Anita Westervelt)

Poecilanthrax lucifer predominantly occur in the West Indies and southern Gulf States. It is a species of bee fly. The larvae develop as parasites inside caterpillars of various cutworms and armyworms, which isn’t a bad thing as those moths are noted as being agricultural pests.


Poecilanthrax lucifer. (Photo by Anita Westervelt)

Hoplitimyia mutabilis, is a soldier fly and honey wasp mimic. There is precious little information about H. mutabilis other than BugGuide.net, mentioning they visit flowers. In general, soldier flies are found worldwide. Adults frequent near larval habitats, mostly in wetlands, damp places in soil, sod, animal excrement and in decaying organic matter, according to Wikipedia.


Hoplitimyia mutabilis, a soldier fly. (Photo by Anita Westervelt)

Genus Hedriodiscus possibly Hedriodiscus trivittatus, also a soldier fly. (Photo by Anita Westervelt)



Mexican fruit fly, Anastrepha ludens. Adult fruit flies feed on flower nectar but are not considered important pollinators. Male flies use their highly patterned wings for courtship. Fruit fly larvae are the bad guys in Texas orchards; they feed and live on fruits, nuts, flowers, stems, leaves and plant roots, and, sadly, for all their adult beauty, they are serious commercial pests in fruit orchards.


Mexican Fruit Fly. (Photo by Anita Westervelt)

Black bee fly, Anthrax georgicus, the cover photo, is a genus of bombyliid flies, commonly known as bee-flies, because of their resemblance to bees. They are mostly dull black with striking wing patterns. Adults feed on nectar and pollen, and some are important pollinators; larvae are mostly parasitoids of other insects, including wasps, flies, beetles, grasshoppers, lacewings, butterflies and moths.


Black Bee Fly. (Photo by Anita Westervelt)


Chrysops flavidus is a species of deer fly identifiable by its yellow legs. Female deer flies are persistent blood feeders, but the males do not consume blood. Instead, they subsist by feeding on pollen and nectar from plants. Larvae are aquatic and feed primarily on organic debris. Chrysops flavidus is a widespread livestock pest in southeastern U.S., Caribbean and Central America. Adult female deer flies lay eggs in masses of 100 to 1,000, on foliage, rocks or in grass in moist soil. The adult female has a blade-like mouthpart to cut through hide in order to feed on blood.


Chrysops flavidus, a deer fly. (Photo by Anita Westervelt)

Genus Efferia, a robber fly. Robber flies exhibit a generalist feeding behavior. A Texas A&M article calls them voracious predators of a wide variety of pests: beetles, wasps, grasshoppers, leafhoppers, wasps and other insects. Another common name for them is assassin flies.

The name robber fly reflects the insect’s notoriously ferocious predatory habit of lying in wait and ambushing their prey in flight. They can take off from a resting position on the ground or on a branch to intercept other flying insects in mid-air. Robber flies are among the few insects that catch their prey in mid-flight. They are active in the hottest part of the day and shelter in vegetation at night.


The larvae, too, are aggressive predators. They live in the soil, in rotting wood and other decaying organic materials and feed on organic matter, other arthropods such as white grubs, worms, beetle pupae, grasshopper egg masses, other eggs, larvae and soft-bodied insects.


And that’s a wrap as we fly out of 2022.

A Robber Fly. (Photo by Anita Westervelt)

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