Monday, August 5, 2019

Episode 484 (8-5-19): True Flies, or Dipterans, are Abundant, Adaptive, and (in Some Cases) Annoying or Worse

Click to listen to episode (4:32)

Sections below are the following:
Transcript of Audio
Audio Notes and Acknowledgments
Related Water Radio Episodes
For Virginia Teachers (Relevant SOLs, etc.).

Unless otherwise noted, all Web addresses mentioned were functional as of 8-5-19.


From the Cumberland Gap to the Atlantic Ocean, this is Virginia Water Radio for the week of August 5, 2019.  This is a revised repeat of an episode from July 2014.

MUSIC – ~ 11 sec

This week, that excerpt of “Little Brown Bats Eating Mosquitoes,” by Timothy Seaman of Williamsburg, Va., opens a an episode about large, diverse group of insects, some of whose sounds you probably hate to hear on a summer day or night.  Have a listen for about 30 seconds to three kinds of mystery sounds, distinguishable among various other nature sounds, and see if you can guess this group of insects.  And here’s a hint: water rhymes with swatter.

SOUNDS - ~29 seconds

If you guessed flies, you’re right!  You heard, first, the buzzing of one of several species commonly called gnats, second, the buzzing of a deer fly, and third, the whine of a mosquito.  Scientists include these and many other insect species in the taxonomic order of Dipterans, or true flies, characterized primarily by having only two wings as adults.  True flies have a life cycle of complete metamorphosis through four stages: egg, larva, pupa, and adult.  While most true fly species are terrestrial, for many species—in fact, about 3500 species in North America—a watery environment is required for the larva and pupa stages of their life cycle.  The aquatic habitat for some species is a moist or wet area on land; other species develop in streams, ponds, or other water bodies.  Perhaps the most well-known true-fly water connection is mosquitoes breeding in all kinds of standing water, from salt marshes to water-filled tree holes to discarded tires.

Deerflies buzzing; mosquitoes biting and transmitting disease; gnats swarming—for these and other behaviors, many true flies are truly hard to like.  But one can at least appreciate two important ecological roles played by true flies: recycling nutrients by breaking down various materials, from manure on land to leaves in streams; and providing food for bats, birds, fish, frogs, and other animals.  In vast numbers in water, on land, and in the air, true flies have vast impacts.

Thanks to Timothy Seaman for permission to use this week’s music, and we close with a few more seconds of “Little Brown Bats Eating Mosquitoes.”

MUSIC – ~ 18 sec


Virginia Water Radio is produced by the Virginia Water Resources Research Center, part of Virginia Tech’s College of Natural Resources and Environment.  For more Virginia water sounds, music, or information, visit us online at, or call the Water Center at (540) 231-5624.  Thanks to Stewart Scales for his banjo version of Cripple Creek to open and close this show.   In Blacksburg, I’m Alan Raflo, thanking you for listening, and wishing you health, wisdom, and good water.


This Virginia Water Radio episode revises and replaces Episode 221, 7-7-14.

Virginia Water Radio thanks Eric Day, Virginia Tech Department of Entomology, for providing information for this episode.

The sounds used in this episode were recorded by Virginia Water Radio as follows:
gnats in Blacksburg, Va., on 6/29/14;
deer fly in Blacksburg on 7/3/14;
mosquitoes beside Pandapas Pond in Montgomery County, Va., on 8/8/17.

“Little Brown Bats Eating Mosquitoes,” from the 2004 CD “Virginia Wildlife,” is copyright by Timothy Seaman and Pine Wind Music, used with permission; this music was previously used as the feature of Episode 78, 9-5-11, and in Episode 263, 4-27-15 on bats and water.  Mr. Seaman’s Web site is  The “Virginia Wildlife” CD was a collaboration between Mr. Seaman and the Virginia Department of Game and Inland Fisheries to celebrate Virginia’s natural resources and support non-game wildlife programs.  “Little Brown Bats Eating Mosquitoes” was composed in honor of Virginia’s Non-Game Wildlife Tax Check-off.  Information about Virginia’s program for contributions to organizations and programs through tax check-offs is available online at

Click here if you’d like to hear the full version (1 min./11 sec.) of the “Cripple Creek” arrangement/performance by Stewart Scales that opens and closes this episode.  More information about Mr. Scales and the group New Standard, with which Mr. Scales plays, is available online at


Deer fly collected from a wooded area in Blacksburg, Va., July 3, 2014.

Three out of four parts of the complete-metamorphosis life cycle in a true fly: clockwise from left are a mosquito larva, two pupae, and adult.  Collected from a roadside puddle in Blacksburg, Va., June 23, 2009.  Micrograph (70x) taken on 7-7-14, courtesy of Eric Day, Virginia Tech Department of Entomology.

Larvae and pupae of the mosquito Aedes vexans in a puddle in a tire track on the Virginia Tech campus, June 10, 2009.  Image first published in Virginia Water Central Newsletter, June 2009, online at  Thanks to Dr. Sally Paulson, Virginia Tech Entomology Department, for identifying the mosquito species.


Used for Audio,

W. Patrick McCafferty, Aquatic Entomology: The Fishermen's and Ecologists' Illustrated Guide to Insects and Their Relatives (Chapter 16: Midges, Mosquitoes, Aquatic Gnats and Flies), Jones and Bartlett Publishers, Toronto, 1998; available online at

R. W. Merritt and K.W. Cummins, eds., An Introduction to Aquatic Insects, 2nd Edition, Kendall/Hunt Publishing Company, Dubuque, Ia., 1984.

North Carolina State University, “General Entomology/Diptera,” online at

Ohio State University Extension, “Midges and Crane Flies,” Fact Sheet HYG-2129-91. Online in July 2014 at; not found online on 8-5-19.

Ann Posegate, The scoop on gnats: the weather they like & why they drive us nuts, Washington Post, 7/26/11.

Purdue University Extension, “Black Flies,” online at

University of Florida Department of Entomology, “Featured Creatures” Web site,

Voshell, J. Reese, Jr., Guide to Common Freshwater Invertebrates of North America, McDonald & Woodward Publishing, Blacksburg, Va., 2002.

For More Information about True Flies or Other Insects

Alan Raflo, David Gaines, and Eric Day, “Mosquitoes and Water,” Virginia Water Central Newsletter, June 2009, pp. 6-15 (Virginia Water Resources Research Center, Blacksburg, Va.), online at

Vincent H. Resh and Ring T. Cardé, eds., Encyclopedia of Insects, 2nd Edition, Elsevier Academic Press, Burlington, Mass., 2009.

Virginia Tech Department of Entomology Insect Identification Lab, online at


All Water Radio episodes are listed by category at the Index link above (  See particularly the “Insects” subject category.

Following are links to some other episodes on true flies.

Episode 268, 6/1/15 – on Chironomids (non-biting midges).
Episode 78, 9/5/11 – on bats and mosquitoes, featuring “Little Brown Bats Eating Mosquitoes” by Timothy Seaman.
Episode 259, 3/30/15 – on avian malaria research.
Episode 381, 8/14/17 – on waterside night sounds.


The episode—the audio, extra information, or sources—may help with the following Virginia Standards of Learning (SOLs).

2013 Music SOLs

SOLs at various grade levels that call for “examining the relationship of music to the other fine arts and other fields of knowledge.”

2010 Science SOLs

Grades K-6 Scientific Investigation, Reasoning, and Logic Theme
1.1, 2.1, 3.1, 4.1, 5.1, and 6.1 – Current applications to reinforce science concepts.

Grades K-6 Earth Patterns, Cycles, and Change Theme 3.9 – Water cycle, including sources of water, energy driving water cycle, water essential for living things, and water limitations and conservation.

Grades K-6 Earth Resources Theme
4.9 – Va. natural resources, including watersheds, water resources, and organisms.

Grades K-6 Life Processes Theme
1.5 – animals’ basic needs and distinguishing characteristics.
2.4 – life cycles.
3.4 – behavioral and physiological adaptations.

Grades K-6 Living Systems Theme
2.5 – living things as part of a system, including habitats.
3.5 – food webs.
3.6 – ecosystems, communities, populations, shared resources.
4.5 – ecosystem interactions and human influences on ecosystem.
6.7 – natural processes and human interactions that affect watershed systems; Va. watersheds, water bodies, and wetlands; health and safety issues; and water monitoring.

Life Science Course
LS.1 – understanding of scientific reasoning, logic, and the nature of science, including current applications to reinforce science concepts.
LS.4 – organisms’ classification based on features.
LS.6 – ecosystem interactions, including the water cycle, other cycles, and energy flow.
LS.8 – community and population interactions, including food webs, niches, symbiotic relationships.
LS.9 – adaptations for particular ecosystems’ biotic and abiotic factors, including characteristics of land, marine, and freshwater environments.
LS.11 – relationships between ecosystem dynamics and human activity.

Biology Course
BIO.1 – current applications to reinforce science concepts.
BIO.6 – bases for modern classification systems, including structures, biochemistry, and developmental stages.
BIO.8 – dynamic equilibria and interactions within populations, communities, and ecosystems; including nutrient cycling, succession, effects of natural events and human activities, and analysis of the flora, fauna, and microorganisms of Virginia ecosystems.

Virginia’s SOLs are available from the Virginia Department of Education, online at

Following are links to Water Radio episodes (various topics) designed especially for certain K-12 grade levels.

Episode 250, 1-26-15 – on boiling, for kindergarten through 3rd grade.
Episode 255, 3-2-15 – on density, for 5th and 6th grade.
Episode 282, 9-21-15 – on living vs. non-living, for kindergarten.
Episode 309, 3-28-16 – on temperature regulation in animals, for kindergarten through 12th grade.
Episode 333, 9-12-16 – on dissolved gases, especially dissolved oxygen in aquatic habitats, for 5th grade.
Episode 403, 1-15-18 – on freezing and ice, for kindergarten through 3rd grade.
Episode 404, 1-22-18 – on ice on ponds and lakes, for 4th through 8th grade.
Episode 406, 2-5-18 – on ice on rivers, for middle school.
Episode 407, 2-12-18 – on snow chemistry and physics, for high school.
Episode 483, 7-29-19 – on buoyancy and drag, for middle school and high school.