Tanks & Fireworks: Bugs of Summer
by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
With the 4th of July upon us, my thoughts turn to creatures that epitomize the sights and sounds of summer, such as the June bug and the firefly. Almost anywhere in the U.S., you'll encounter these bugs on your doorstep or flickering in the night sky. Most of us have caught one or the other in glass mayonnaise jars. One in every four species of animal on the planet is a beetle. The group comprises about 40 percent of known insect species, with the most diversity of any animals on earth.
June bugs, also called May or June beetles, are scarab beetles in the genus Phyllophaga. There are over 200 species in North America. These red-brown beetles commonly appear in the Northern Hemisphere on warm spring evenings and are attracted to lights. Heavy-bodied, they are 0.5 – 1 in. (1.2 – 2.5 cm) long and have shiny wing covers. Dead giveaway features include spiny legs that stick to everything including your screen door and your hair, and a very clumsy method of “flying.” The adults emerge as early as late April in southern states and much later (June-July) as you travel further north into Canada. June beetles are classified in the phylum Arthropoda, (jointed feet), class Insecta (6 legged), order Coleoptera (beetles/sheafed wings), family Scarabaeidae (Scarab beetles), and subfamily Melolonthinae (chafer beetles). My pick of the week for super cool websites that show tons of photos of these guys is http://bugguide.net/ which is hosted by Iowa State University Department of Entomology. To add to the confusion, in some parts of the country, a “June bug” is actually a green June beetle with a much more triangular shape (Cotinus nitida).
Steven Katovich, USDA Forest Service, Bugwood.org" allowable educational use
June Bugs live up to their genus name of Phyllophaga, which comes from the Greek words phyllon, which means "leaf," and phagos, which means "eater." The adults are called chafers for their leaf munching skills because they gnaw the leaves and flowers of many deciduous trees, shrubs and other plants. June bug larvae are white grubs (reaching 40-45 mm long when full grown) that live in the soil and feed on plant roots, especially those of grasses and cereals, and are occasional pests in pastures, nurseries, gardens, and golf courses. Evidence of white grubs munching on grasses shows up as poorly growing patches that quickly turn brown in dry weather. The grubs can be found immediately below the surface, usually lying in a characteristic comma-like position. Just a few species are responsible for most of the turf damage encountered in lawns and most control methods do more damage to beneficial insects than to the target bug.
So why are they called May bugs and June bugs? They are named for the month in which we see them flying around looking for mates. Most of the time, the ones hitting your screen door are males, the females are typically heading off to the “nursery” already gravid with eggs. After feeding several nights and mating, females burrow into moist soil to a depth of 2-6 inches where they lay 20-50 eggs individually packed into balls of soil. These eggs must absorb moisture from the surrounding soil to develop. After 20-40 days, the eggs hatch and the young larvae burrow upwards in search of plant roots. Commonly called white grubs, the “c”-shaped, cream-colored bodies resemble inch-long maggots with six tiny legs. Underground, they dine on dead plants or any roots and organic matter they can reach, then they hibernate through winter. Each species seems to prefer to feed on a particular variety of plant roots, though some feed on any organic matter present in the soil. Their life cycle can be from 1-4 years with shorter cycles in the far south and longer larval development times in the northern U.S. The adults emerge from the soil at dusk and fly to trees and shrubs for a meal of foliage. If the evening temperatures are high enough, the adults continue feeding until dawn when they return to the soil for hiding. Very high populations can severely defoliate preferred plants such as oaks and maples.
The beetles are nocturnal, and extremely attracted to light, which is why we have huge piles of them on our porches. Scientist think their strong light attraction is an navigational tool designed to work with sunlight or moonlight and other far away lights that is stymied or thrown off by our use of outdoor lighting. June bugs make a pretty loud buzzing sound during flight due to their large and ungainly form, obviously stealth is not their strong suit. Ventral hair (hair on the underside of their bodies) is a characteristic of these beetles. Their natural habitats are deciduous forests and grasslands and, of course, agricultural fields, golf courses, and suburban lawns with a range that includes most of North America and parts of Europe.
These beetles are actually good eating! Check out this video (http://www.spike.com/video/bizarre-foods-june/3064489 ) of the Travel Channel Show Bizarre Foods with Andrew Zimmern to see June bugs prepared three ways. This article (http://www.wwmag.net/junebug.htm) in Volume 2, Issue 4 of Wilderness Way magazine gives more information on the nutritional value and sweet nutty taste of June bugs. By the way, although some people really hate these beetles, they are harmless and cannot hurt you; so there is no reason to kill them. If you want to reduce the number on your deck, turn off your lights at night or switch to yellow bulb which are less attractive to them.
So besides humans, what eats June bugs? June bugs make excellent bait for fish and they are used for catching everything from catfish to bass. Early almanacs told farmers to put pigs into their fields if a white grub infestation was suspected as the little porkers love to root out the nutritious beasts. Birds and toads also eat the adults and moles, raccoons, and skunks will eat the grubs. June bug populations have been theorized to be on the decline as compared to the 60s and 70s due to an abundance of pesticide use for control of the bugs in agriculture and turf management.
Last but not least, some favorite June bug activities from my childhood: wearing a June bug as a “brooch,” tying fishing line or other very light string to one leg of the June bug and flying them like a awkward airplane, June bug races (requires patience), and the ever popular game of throwing them on your younger brother or sister.
Now for the fireworks, the warmth of summer nights (at least the 1-2 we have had so far) brings out fireflies. Fireflies, or lightning bugs, are beetles (same order as June bugs: Coleoptera) from the family Lampyridae. The larval form and larvae-like females (larviform) of some firefly species are sometimes called glowworms to distinguish them from the winged forms. There are about 2,000 firefly species. These insects live in a variety of warm environments, as well as in more temperate regions, and are a familiar sight on summer evenings. Fireflies love moisture and often live in humid regions of Asia and the Americas. In drier areas, they are found around wet or damp areas that retain moisture. Some fireflies are strictly crepuscular creatures which means they are primarily active during twilight as opposed to nocturnal (true night-time loving) and diurnal (daytime) animals. Fireflies have a lifespan of about two months and can grow to a size of one inch (2.5 cm). Not all adult firefly species glow, but most of the larval forms do.
Fireflies get their name from the bioluminescence coming from a light-producing organ in the beetle's abdomen that contains a substance called luciferin (a substrate) which when combined with luciferase (an enzyme), ATP (adenosine triphosphate), and oxygen reacts chemically to release energy in the form of light. This chemically-produced light, emitted from the lower abdomen, may be yellow, green, or pale red in color, and has a wavelength from 510 to 670 nanometers. The eggs, larvae, and pupae of members of this family are often luminous as well as a way of signaling predators that they are not tasty (and in fact are mildly toxic). A firefly's glow is an extremely efficient process converting 90-100% of the energy to light instead of heat. The average incandescent light bulb only converts 10% of its energy to light, wasting the rest as heat.
So why do the adults glow? Well, just as one would think, to pick up a date (or a meal as we'll see below). Around dusk, the male takes to the air and flies over and around vegetation, flashing its species-specific code. The female, usually perched on vegetation, responds by mimicking the signal a few seconds later. After five to ten signal exchanges, the male will have homed in, and mating takes place. Aspects of male flash patterns are also thought to be affected by sexual selection. Female fireflies have been shown to prefer certain characteristics of a male's photic signal (such as increased flash rate) and respond preferentially to males that possess these "sexy" signal components (Branham, M.A. and M.D. Greenfield 1996. Nature 381:745-746). Where this light dance goes horribly awry for one of the pair is when it involves the female of the genus Photuris, a large eastern U.S. Species, who is the “femme fatale” of the firefly world. She is capable of mimicking the flash code of other species and thus lures in many different males – not for mating but for eating!
Females deposit their eggs in the ground, which is where larvae develop to adulthood. Underground larvae are predators and feed on worms and slugs by tracking them down via their slime trails and injecting them with a numbing fluid (a perfect B-Movie script). Adults typically feed on nectar or pollen, though scientists believe that some adults might not eat at all. For more information go to the Firefly Files at http://iris.biosci.ohio-state.edu/projects/FFiles/frfact.html. According to this site, it is rare to find a flashing firefly west of the middle portion of Kansas and scientists are not exactly sure why. It may be related to the firefly's natural gravitation to wetter climates, but some arid species exist. Yet another mystery for the future entomologists of the world.
To attract fireflies to your yard, cut back on pesticides and outside light. One of the reasons why summer, although chilly, can be enchanting on Nantucket is our limited light pollution which makes it easy to pick out these glowing beauties which have been around for a couple of weeks. Get out there and enjoy the bugs of summer.