Why Are There Dragonflies on My Car?

Blue eyed darner, Rhionaeschna multicolor, flying

Blue eyed darner, Rhionaeschna multicolor, flying

I’ve been thrilled by the recent swell in the number of dragonflies out and about.  There are a lot of dragonflies flying this year, and they’re out earlier than usual.  Not everyone is happy about the glut of dragonflies though and several people have already written to me to ask how to get rid of the dragonflies in their yards.  I get several of those e mails every year, so that’s not unusual.  However, I’ve had a lot of people asking me why there are dragonflies hovering around their cars and that is odd.  I’ve responded to a good 15 e mails about this in the past week alone when I normally get somewhere between 2 and 4 a year.  Rather than typing out the same thing over and over to every individual who writes to me, I thought a blog post was in order.  So, today I give you the answer to the mystery of why there are dragonflies flying around your car!

Dragonflies require water to complete their life cycle.  The adults fly on land, but they start their lives in water.  Most dragonflies lay their eggs in water.  When they hatch, the nymphs develop underwater, feeding and growing until they are ready to molt into adults.  At that point, they crawl up a piece of vegetation or onto the shore, break out of their nymphal skin, puff out their wings, and fly away as a brand new adult.  Dragonflies spend the majority of their lives in water, often 10 months (or more!), before spending a month or two on land as adults.  Then they repeat the process and start the next generation.

For this to work, dragonflies have to be able to find bodies of water in which they can lay their eggs.  Luckily, they are able to do so!  They simply fly about and look for a particular pattern of polarized light.  When they see that pattern of light, they know that they’ve found water and can get down to the serious business of forming and defending territories, finding mates, and laying eggs.  That pattern of light is incredibly important for dragonflies, so it is highly attractive to them.

flame skimmer

Flame skimmer (Libellula saturata) resting on a car antenna

Unfortunately for the dragonflies, humans came along and started building cars.  Some of those cars give off the same pattern of polarized light as water, especially red or dark-colored cars.  As far as the dragonflies are concerned, a red or dark car IS a body of water because it gives off the correct light signature.  The result is that dragonflies mistake cars for bodies of water and go about doing what they normally do at water: making territories, finding mates, and laying eggs.  You might see a male dragonfly perched on your radio antenna.  He’s likely defending your car as his territory.  You might see two dragonflies mating above you car, indicating that a female decided that the “water” she found is an acceptable place to lay her eggs.  Sometimes you’ll just see a dragonfly bouncing up and down off the hood of your car.  That’s the female laying her eggs as she would in a pond.  Of course her eggs end up splattered across your car rather than in a pond, so they’re never going to hatch.  That’s bad for the dragonflies, and sometimes bad for you too.  Occasionally the eggs can cause minor damage to your car’s finish if they’re allowed to remain in place for extended times.

If you have a lot of dragonflies around you car, it’s best to try to discourage them from trying to lay eggs.  I have a white car and couldn’t care less about the finish (my vehicle is a field vehicle – you can tell), so let me state up front that I have very little personal experience with preventing dragonflies visiting my car.  However, I do have a few suggestions for things you can try:

1. Cover your car when it is not in use.  This is a huge pain, I know, and it makes you look like one of “those people” who are obsessive about protecting their cars.  However, if you are in an area where there is a lot of dragonfly activity and you repeatedly have problems with dragonflies laying eggs on your car (they’ll be visible as little yellow streaks or blobs), this is a surefire way to keep the dragonflies off your car’s finish.

2. Park in the shade whenever possible.  Parking under a tree will make your car less obvious from above.  It will also decrease the light hitting your car and reflecting off.  This should reduce the attractiveness of your car.

3. Try waxing your car.  I’m guessing here, but light reflecting off wax will likely have slightly different properties than light reflecting off the clear coat on your car.  It might be just enough to discourage dragonflies.  Wax should also add an extra layer of protection between the dragonflies and your car’s finish.

4. Start carrying a spray bottle of water and a rag or paper towels in your car to wipe off any eggs you see.  It’s easy to do a quick walk around of your car a few times a day and simply wipe away any eggs you find.  Getting them off your car as soon as possible should help minimize any damage the eggs might cause.

Yellowstone River

Natural water, where aquatic insects should lay their eggs

Discouraging dragonflies from visiting your car is a good thing.  Apart from the small risk of dragonfly induced damage, there is some real concern that the attractiveness of cars to dragonflies may eventually lead to a decrease in dragonfly populations.  Dragonflies need to find water to complete reproduction and they are unable to do so if they’re distracted by cars.  Some buildings, dark gravestones, solar panels, and other man-made objects are attractive to dragonflies too.  And dragonflies aren’t the only insects fooled by cars either!  Mayflies, horse flies, and other insects with aquatic stages have similar problems.  Eventually, we might need to reconsider how we build our buildings and finish our cars to protect aquatic insects, but anything you can do to discourage aquatic insects from mistaking you car for water is good for you and good for the insects – a real win-win for everyone!

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Additional Reading

György Kriska, Balázs Bernáth, Róbert Farkas, and Gábor Horváth.  2009.  Degrees of polarization of reflected light eliciting polarotaxis in dragonflies (Odonata), mayflies (Ephemeroptera) and tabanid flies (Tabanidae).  Journal of Insect Physiology 55: 1167–1173.

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth