SEPTEMBER
1998

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

9-10-98

Last Glow of Summer for the Insect World

They are the dying embers of the blazing fire of summer insect life. Glowworms, the immatures of fireflies, provide the finale, the curtain call for the season of insects.

Glowworms, like adult fireflies, have the ability to produce light. Unlike their parents, however, glowworms do not flash. They produce a constant glow, which is the basis for their name.

Many people have never basked in the glow of a glowworm. Unlike adult fireflies, glowworms do not produce aerial displays that are hard to miss. Glowworms, like all immature insects, are wingless. They crawl on the soil surface or live in the soil. Generally, they are out of sight and, therefore, out of mind for most humans.

Most glowworms are associated with moist environments. Swamps, creek banks and edges of ponds are prime glowworm habitats. However, large concentrations of glowworms have been spotted in drier areas, such as in the leaf litter of an oak wood.

Glowworms are predators. They feed mainly on slugs and snails but also will make a meal out of other soft-bodied creatures like caterpillars.

Without their lights, glowworms are hard to spot. They are brown to black colored and blend in nicely with moist soil. To most people, glowworms resemble those creatures we know as pill bugs or sow bugs. Pill bugs are not insects but are common creatures found in decaying plant material, such as compost piles or mulched flower beds.

If you want to see glowworms, you need to head out to a creek or pond. Dark nights work best since the lights are difficult to see in bright moonlight or, for that matter, under a street light.

Patience is a virtue when it comes to glowworm viewing. Glowworms are somewhat shy creatures, so when they are disturbed they douse their lights. A person walking through their habitat will prompt a mass extinguishing of the little lanterns.

So, if you go looking for glowworms, walk into the area and stop. As you stand quietly, focus your eyes on one spot. Stare at the spot as you might stare at a 3-D picture. Suddenly, the glowworms will reward you with first one and then other little blue-green lights. Once you have spotted the light, you will find them everywhere.

One of the great scenes for nature lovers is to witness literally thousands of glowworm lights lining their favorite stream bank on a dark night. It is an awesome sight.

Generally, scientists cannot explain the function of the light for glowworms. One suggestion is that the light allows them to mark their territory. It also has been suggested that the light works as a reverse-flash protective device. The insect is easy to see with its light on but when disturbed, it turns the light off and moves. This makes it difficult for a predator to find it again.

Whatever the biological reason, the little lights of immature fireflies are another miracle of nature. Glow little glowworm, glow!

 

Writer: Tom Turpin
Editor: Olivia Maddox