COME TO THE LIGHT!!

A Bugs Life is one of the most popular digitally animated movies about insects. It was made in a while ago, in 1998, but still remains a classic despite the digital film advances since then because of its witty humor and detailed observations about insect life. One classic joke is when Flick the ant, the main character, arrives at the insect "city" and encounters other types of insects. His arrival at the city opens with two insects being drawn to a bug-zapper light, with one warning the other "don't look at the light!!" as his partner slowly swirls closer to it, exclaiming "I can't help it!!" as he get zapped.

Don't look! Image from http://www.kwaree.com/blog/wp-content/uploads/2007/05/bug-zapper.jpg

    The reason everyone laughs at this joke is because almost everyone knows that many insects are drawn to artificial lights at night. This is why bug-zappers work, and why you'll find a pile of dead insects under your porch light [or in your porch light, if its not sealed correctly!]. Its so ubiquitous in our culture, there even is an iPad app for bug zapping. Even before electricity insects were noted for being drawn to candle light. If you search on Google for "Poem, moth, candle" you get over 1 million references for poems about moths being drawn in a death waltz with a candle flame. So, why are insects drawn to the light that it makes it an effective trap?
     Many insect groups are drawn to light because of a property called phototaxis, which is an organisms to or away from light [photo=light, taxis=movement]. Many insects are actually negatively stimulated by light, and run to darkness. Cockroaches are a good example of this...turn on a light in a room full of them, and they go hide. Most other insects, however, are attracted to light, especially at night. This is because many groups of insects, especially flying insects such as Lepidoptera (moths) and Diptera (flies, mosquitoes) use the moon for navigation at night. Before electric lights and other artificial lights came about by humans in the last couple of centuries, moon light was the strongest light source available at night. By using the light to orient themselves, they could migrate, and find new habitats.

What the insects adapted to use to navigate, until we hijacked their system. Flynn, Texas

    The way the phototaxis works is one sensor on the bugs (often the eyes) gets the information from the light as wavelengths, and the insect then turns in the direction of the source of the light so both sensors or eyes get the same amount of light. This turning towards the direct of the light causes an insect that passes the bug zapper to pick up the light information, turn towards it, then slowly keep getting in closer. It keeps getting closer and closer with tighter circles around the light, until its zapped by the light's electrical current. Using just light, and not the zapping part, many entomologists can draw in insects to observe their behavior and collect specific ones that they need to study (this is called spot lighting, UV lighting, or using light sheets), and leave the other insects they are not interested in alone.

Fellow entomologists being creative by using a white garage door as a "light sheet"

      While bug zappers are effective at killing insects, its often effective at killing both "good" AND "bad" insects. Most people purchase bug zappers to kill mosquitoes, which are annoying due to their bites and dangerous because they can transmit diseases. However, bug zappers are effective at killing insects like moths which are good pollinators in some cases, beetles that are good predators of garden pests, and various other insects that happen to use the moon to navigate in their otherwise harmless lives.
    So, the lesson here? Before humans brought artificial lights, many insects used the moon at night to navigate. However, when we brought in much brighter light sources that are actually within reach of the insects in flight, we were able to take advantage of it for trapping them and studying them. Next time you see bright light at night swarming with insects, come to the light yourself and see what other six-legged friends are drawn to it. Have a good week!