Tuesday, February 25, 2014

Moth Fly in the Men's Room

We, like most of the country, have had a colder than usual winter.  Of course, I am in Texas, so compared to people repeatedly digging out from under feet of snow I can't complain, but it has been cold enough to keep me out of the field.  No problem though - insects are everywhere - including just down the hallway in the men's room.

I first spotted these little guys many months ago and thought, "Flies in the bathroom.  Maybe someday I will take a look at them."

Collecting in the bathroom is a lot warmer than collecting outside right now, so get ready to meet the moth fly.

This image was taken with my cell phone camera in the bathroom.  The fly is on the tile wall, not in the urinal.  (Even I have some limits as to where I will collect.)  Yes, the legs and shoes reflected off the tile are mine.

Note the white spots on the wing edges and on the legs.  The scientific name for this little guy is Clogmia albipunctata.  I don't know the root of clogmia, but alb is from the Latin albus, which means "white",  and punctus is from the Latin for "spotted."  White spots.
Clogmia albipunctata has lots of common names - moth fly, moth midge, or drain fly to list a few.  This is an image of a living fly inside of a Petri dish.  Note the scale bar - these insects are small.
A ventral view of the moth fly hanging on the upper lid of a Petri dish.  The wings are iridescent.

In this image Clogmia has managed to get itself stuck to the lid of the Petri dish via static electricity.  Not only are these flies small, but they are amazingly hairy which makes them hydrophobic.  According to Borror and DeLong's The Study of Insects, the larvae have hydrofuge hairs - water shedding hairs.  I also think that is the function of the hairs on the adult flies, making it possible for them to enter drains to lay eggs without being wetted and getting stuck due to surface tension and the adhesive properties of water.
In this image Clogmia is standing on the side of the Petri dish looking straight up at the dissecting scope.  Note the plume-like antennae and the white spots on the legs.
The next set of images were made with the flies in 70% isopropyl alcohol.  The alcohol preserves the insects.  Also, filling the Petri dish so that the insect is completely submerged eliminates unwanted glare.  I learned this trick from Dr. Joe Rutledge at Children's Medical Center in Dallas about 30 years ago.

Head-on view showing the plumose antennae and the halteres or vestigial wings of the fly.    
All flies have only two functional wings.  In fact, that is the easiest way to identify an insect as a fly.  It's order name is Diptera.  Di- means "two" and ptera means "wing".  The other two wings are reduced to counterweights called halteres.  Halteres also flap and are thought to help stabilize the insect during flight.  The halteres are visible in the image above as two tan blobs just above the legs and below the tufts of whitish hair on the side of the thorax.

This image is a composite of two images taken with the digital dissecting scope.  One of the most unexpected features of this insect are the plumose antennae.
Small insects can be difficult to work with.  They are easily damaged and the mounts we use for the electron microscope are disproportionately large for the insect.  Below are some images of the mounting I engineered for the moth flies.  These images will also give you some idea of the fly's actual size.

To make sure I can see most of the insect I mounted it on a regular sewing pin.  The pin is held in place with a strip of double-stick copper tape.

How do you attach an insect to a sewing pin?  Super glue.  I often use wood glue but the hydrofuge hairs on the insect repelled the glue since it is water based.  
In this image you can see the size of the moth fly in relation to a penny.

The images below were made with the Hitachi S3400-N Scanning Electron Microscope.

Head and eyes

The head of Clogmia.  [138x]
In this image you can see the ommatidia, the plumose antennae, and the scales on the legs.  Everyone is familiar with the fact that moth and butterfly wings are covered with scales, but until I began imaging insects I never realized the some flies also have scales.  (In a previous blog you can find images of a bee fly, which also has scales. http://tinyurl.com/kd8ntrk)  [95x]
Ommatidia of the eye.  [500x]
Ommatidia - approximatley 21 microns across.  [1,390x]


Wing at 50 x magnification.  The entire wing is only about 2mm from base to tip.
This image shows the hairs on the margin of the wing.  [37x]

Wing surface [130x]

The white spots on the wings are caused by dense patches of hairs.  [160x]

The dense hairs that make up the white patches are flattened scales.  [456x]

Close up of some of the hairs on the wing.  [2,000x]


The structure of the moth fly antennae are complex and wonderful.  

Middle segments of an antenna.  [189x]
Terminal segment of antenna with sensory structures.  [349x]

Connection between antenna segments.  Note the sensory openings.  [901x]

Sensory openings on the terminal segment of an antenna  These opening are between 1 and 2 microns - bacteria sized.
More sensilla on the terminal antenna segment.  [4,000x]

Now for the bad news - Bacteria

The larvae of Clogmia albipunctata grow on the slime inside of bathroom and kitchen drains, at sewage disposal sites, and in garbage cans.  They can serve as mechanical vectors for human diseases. (Ahmen)

In 2012 The Journal of Hospital Infection reported that for the first time Clogmia albipunctata has been found in Germany and is becoming a problem in German hospitals. Forty-five bacterial species were found to be colonizing Clogmia. (Faulde and Spiesberger)

Bacteria on basal segment of antenna.  [750x]

Coccus bacterial and bacillus bacteria (arrows) on hairs of antennae.  [4,000x]
Coccus bacteria on serrated hairs of Clogmia.  [8,500x]

Some of these structures, which may be bacteria, seem to be attached to the serrated hairs by a stalk.  [1,710x]

The arrow indicates a tuft of hair just below the wing.  The tip of the sewing needle is the large object at the bottom of the image.  The head of the insect is to the left of the image.  [40x]

Same tuft of hair.  You can see that some of the hairs got stuck in the super glue I used to mount the insect.  Bacterial are obvious even at this magnification.  [130x]

The tuft hairs are covered in bacteria.  [600x]

At this magnification you can see what appear to be hairs with structures that seem to really hold bacteria.  [2,500x]

Knob-shaped projections are about 500 nm across.  [4,000x]

Coccus bacteria with a diameter of 2 to 3 microns attached to knob-shaped structures on hairs. [2,500x]

Observations, conjecture, and suggestions for future work.

Why would moth flies have what appear to be specialized hairs for holding bacteria?

Could the bacteria be a food source?  I did notice that even though there were lots of bacteria near the base of the antennae, there were none farther out - exactly what I would expect of a fly cleaning its antennae. 

If not a food source, could this be how the adult fly insures that the bacteria its larvae need for food are always on hand? Complex structures are expensive for an organism to make and maintain.  If the organism is going to expend the energy to make a structure it must have a benefit, otherwise that structure would be selected against by natural selection.

Though I am not set up for it in my lab, it would be a great project for someone to culture and identify the bacteria present on our moth flies.

Also, it would be a pretty neat experiment to sample the bacterial  populations present in a drain without infestation of moth flies and then introduce moth flies and repeat the survey.

When I first discovered these little flies I didn't expect to find such an interesting subject.  I ended up with ninety-two finished images that I could have used in this blog.  

A gentle reminder that all images are covered under a Creative Commons license. You MAY copy, reproduce, modify and use any of these images in any way you like just as long as you credit Eastfield College, Mesquite, TX, and don't sell them.


Ahmen, A.  Insect vectors of pathogens in selected undisposed refuse dumps in Kanduan Town,northern Nigeria.  Science World Journal [serial online]. December 2011;6(4):21-26. Available from: Academic Search Complete, Ipswich, MA. Accessed February 25, 2014.

Borror, D. J., & White, R. E. (1970). The Peterson Field Guide Series: A field guide to insects of America north of Mexico. Boston, MA: Houghton Mifflin. 

Faulde, M., & Spiesberger, M. (2013). Role of the moth fly Clogmia albipunctata (Diptera: Psychodinae) as a mechanical vector of bacterial pathogens in German hospitals. Journal of Hospital Infection83, 51-60. Retrieved from  http://www.sciencedirect.com 

Jaeger, Edmund C. A Source-Book of Biological Names and Terms. Springfield:
Thomas, 1972. Print

Triplehorn, Charles A, Norman F. Johnson, and Donald J. Borror. Borror and Delong's Introduction to the Study of Insects. Belmont, CA: Thompson Brooks/Cole, 2005. Print.


  1. Its incredible the images that you took with the Hitachi SEM! Its a whole different world at the micron level. On a side note I find it cool that one of your sources uses flies collected from a dump in northern Nigeria!

  2. Thanks! These little guys seem to be in a lot of places an spreading. The other article of interest was about their discovery for the first time in Germany.

    I am delighted you like the blog.


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