The Science of Glow-worm Beetles By Erin Mae Dul.
The more popular, yet less-encountered glowing insects pictured above belong to the beetle family of Phengodidae, or in layman’s term glow-worm beetles, or glowworms. In the first, top image is a male glow-worm beetle in adult form; the branched antennae that almost look like the bone structure of a pair of wings aid in the detection of female glow-worm pheromones.
There are three stages of life for glow worms. The females start at the egg stage, as do males, before birthing into larvae. After larvae it takes 12-13 days for the females pupation into Zarhipis integripennis, and 20-35 days for the males.
Although the name gives a simplified explanation of the beetles’ luminous abilities, it is still a little known fact that not all glow-worms actually glow, and it is actually the females in apparent larviform who are able to produce a glow. The paired photic organs that produce the light found on adult females are located on each body segment, one spot for each side, which are said to resemble train-car windows lit up at night, earning them the nickname of railroad-worms. Sometimes these photic organs manifest into luminous bands between each body segment as opposed to singular spots.
Unlike the female glow-worm, males are not in larviform, rather resembling other beetles. The male glow-worms boast two pairs of wings, along with the branched, feather-like antennae that are present within males of most species. However, it should be noted that in certain documented instances, it has been found that larvae as well as the males within the Mastinocerini tribe [as well as others] produce a luminous glow from their larval photic organs, which like the respective female photic emissions, are believed to serve as a defensive function.
Even though the females, larvae, and with some exceptions certain males, of the glow-worm beetle family may glow brightly, they aren’t always easily found. If one was inclined enough to look, it would be best to search for these glowing insects at night, which is when they are suspected to be most active, either within moist soils or on the bark and leaves of trees, preferably in a tropical region with high above-ground moisture levels. Similar to worms, glow-worm beetles seem to enjoy coming out onto the ground surface after a summer rainstorm. Since they are not one of the more commonplace insects that humans happen to come across without meaning to that even when they are found, they aren’t always recognizable to layman’s eyes, especially during the daytime when their glow is more subdued.
So if you’re out on a warm, moist night, make sure to keep your eyes open, and remember that glow-worm beetles are not the only bioluminescent creatures crawling around on the ground. If you see something glowing in the grass, or on a tree, put that scientific curiosity to use and see if you can figure out what it is. Even if you can’t make a good educated guess, it’s still an amazing natural phenomenon to witness, and definitely one to not forget.
- Read more about glow-worm beetles here.
- Read more about how bioluminescence works, and what other types of creatures from around the world produce luminous glows here, here, and here.
Image Credits [From top to bottom]: First image, Colin Hutton | DeviantArt | Flickr. Second image, James E. Lloyd, University of Florida. Third image, James E. Lloyd, University of Florida.