It was eerie. The patches of blue-white light amongst the leaf litter under the live oak tree were unusual. What could be causing this phenomenon? Bioluminescent fungi? Fireflies? Something else?
After a bit of investigation, we decided that this glow was probably produced by the larvae of click beetles. Click beetle larvae are sometimes called wireworms and they live in soil and leaf litter for several years. Most of them are said to glow. And the adults have two bioluminescent spots on their heads giving them the appearance of having glowing yellow eyes. They are not very big, only about an inch long, and resemble fireflies (except the light is in the wrong place).
Click beetles resemble fireflies because both of these insects are beetles. A beetle is an insect with its front pair of wings hardened into wing-cases. These wing-cases flip up and the flying wings are unfolded from below so the insect can fly. Examples of beetles include ladybugs, June bugs, lightning bugs, and cockroaches (ugh!). If you’ve ever watched a ladybug take flight, you have seen how it lifts its wing-cases to release the delicate wings. All beetles are designed this way.
Not all beetles exhibit bioluminescence, of course. However, the click beetle’s eyespots and the lightning bug’s glowing abdomen are well-known. You may have not seen many click beetles, but chances are you have had experience with lightning bugs or (aka) fireflies. Since they are neither true bugs nor flies, they really deserve a better name. Other than the genus name, Photinus, there isn’t one. In fact, where you live in the United States pretty much determines what you call this insect. In New England and in the West, people usually call them fireflies, while in the South and Mid-West, we say lightning bugs.
I grew up in Central Texas and the term “lightning bug” was the one we used. Lightning bugs were a staple of summer nights’ entertainment. People would pull out lawn chairs and enjoy the relative cool of twilight and watch the light show. Kids would catch a few of the hundreds of glowing insects and put them in a mason jar. I remember going to sleep watching the flashes. Do you have similar memories?
Have we lost our lightning bugs? There certainly has been a decline in numbers and in the diversity of lightning bug species. According to TPWD, there are about 175 species of lightning bugs in the United States, and 36 species are known from Texas. However, even dedicated firefly enthusiasts rarely observe more than just five species. In some areas, only one species is encountered. What happened? Well, as you probably suspect, people happened. Fireflies prefer moist vegetation and long grasses in habitats with native plants, brush, and woodlands. These kinds of habitats have been declining for decades. Although “mosquito sprays, ravenous fire ants, and light pollution” have all been proposed as causes for the decline in lightning bugs, a May 20, 2019 Texas Monthly article by John Nova Lomax also points out that “each theory on its own is insufficient.” Lomax suggests that “habitat destruction—unspecified” may be the root cause. “While they can withstand fire ants, mosquito toxins, and light pollution, perhaps it’s just that they can’t handle not all three and the wholesale paving over and/or manicuring of the grassy fields and well-watered woodland edges they favor.”
In suburbia and in rural areas you should still be able to see fireflies. That is if you leave some suitable habitat, don’t use pesticides, turn the lights off, and if it is not too dry. Drought is a serious problem for fireflies and not one we can correct. Still, if creeks, ponds and their accompanying vegetation exist in an area, there should be some fireflies. So, I have been watching for them.
Here in our corner of the Brush Country I have been seeing lightning bugs flashing about an hour after dusk on nights when the temperature is above 75 degrees. Their flashes seem to occur about every four seconds. They do not appear to form flash streaks. With this information, I can go to the firefly.org website and possibly identify our species. This wonderful website has a “Flash Guide to Texas Fireflies” as well as lots of other information on this charismatic insect. The website even tells you how to catch a firefly! Of course, both the website and I urge you to not harm the delicate insects and to release them to carry on their life cycles. After all, the flashing is the fireflies’ means to attract mates and to make more fireflies.
So, go out after dark and look for lightning bugs. Take a child and introduce him or her to these amazing creatures. Make memories (and remember yours) about a fascinating aspect of nature!