No, this is not an account chronicling a British invasion, especially during the month we celebrate the country’s 250th anniversary of its separation from commonwealth rule. This is instead a short introduction to some of the numerous regional insects of the order Coleoptera.
Globally, there are somewhere between 300,000 and 2 million or more species of beetles, depending on who’s doing the enumerating. A commonly settled upon number is 400,000, which makes beetles account for about 40% of the known insect species and 25% of the animals in the world. In the United States, there are almost 30,000 species.
Morphological variation among individuals in a population of beetles is easily observed. These differences often manifest into adaptations that provide a survival advantage and speciation. It therefore comes as no surprise that beetles were among the life forms studied by Charles Darwin as he pondered natural selection and preparation of The Origin of Species.
During the nineteenth century, Professor Samuel Stehman Haldeman and other members of the Linnaean Society of Lancaster City and County made sizeable collections of beetles. Haldeman mentored society treasurer Simon S. Rathvon’s interest in the insects and he in turn curated the 12,000 beetles in the society’s holdings. The beetle case seen in the photograph is on display at the North Museum on the campus of Franklin and Marshall College in Lancaster. Many of the Linnaean Society of Lancaster City and County’s specimens were moved from the custody of the college to the museum upon its opening in 1953. (For more on the Lancaster Linnaeans, see our post from February 25, 2018, titled “A Century of Extinction” or, better yet, visit the North Museum.)
If it’s organic, living or dead, a beetle has probably become specially adapted to fill the role of reducing it or consuming it. Beetles are indispensable members of the ecosystems they inhabit. Many function as scavengers, breaking down dead plants or animals into the basic nutrients that renew life. There are those that consume rotting wood, dung, and carrion. Sometimes they eat these things when people would rather they didn’t—such as moist wood that’s part of a house. Then there are species of beetles that are herbivores, consuming plants and parts of plants that got their energy directly from the sun. There are beetles that eat stems, roots, leaves, buds, flowers, nectar, sap, seeds, and fruit—many specializing in particular plant species or families. Some of these beetles come to our attention because their populations explode in response to our creation of monocultures of their favored food, but many more act as pollinators for plants critical to human survival. Linnaean Society treasurer Rathvon made these herbivore-plant relationships the focus of many of his nineteenth-century writings, particularly as they affected agriculture. On the upper trophic levels, there are the predatory beetles that feed on herbivores or other carnivores. Many of these species have narrowed their choice of prey to one or fewer species. For example, there is a beetle that feeds only on the subterranean nymphs of cicadas.
Beetles occupy numerous trophic levels within the food chain. Staghorn or stag beetle (Lucanidae) larvae are reducers that feed on rotting wood. Meanwhile the adults, which are sometimes attracted to man-made lights, consume sap. A herbivorous primary consumer, the Red Milkweed Beetle (Tetraopes tetrophthalmus), a member of the long-horned beetle family (Cerambycidae), feeds exclusively on Common Milkweed. Ladybird beetles (Coccinellidae), also known as ladybugs, are secondary consumers and favorites of gardeners due to their appetite for aphids throughout most of their lives. (Click the image for a larger version)
Ladies and gentlemen, the beetles…
The Dogbane Beetle (Chrysochus auratus) is one of the leaf beetles (Chrysomelidae), a family which includes numerous agricultural pests. However, as its name suggests, this beetle feeds on dogbane (Apocynum species), a milkweed-like plant of woodland edges and early successional habitats, so it poses no threat to crops or ornamentals.The large family of scarab beetles (Scarabaeidae) includes dung beetles and other important detritus-feeding decomposers. The may beetles, also known as junebugs, seen here are probably of the genus Phyllophaga, but species-level identification typically requires lab examination.Adult may beetles feed on a variety of leaves throughout the night. The larvae consume the roots of grasses and other plants. Neither life stage does significant damage, but skunks have a passion for digging in lawns to find the larval grubs.Like the others shown in our images, these may beetles were photographed after being attracted to man-made lighting. They’re frequently very noisy when tumbling in for a visit because their soft wing membranes, seen here protruding from the beetles’ posteriors, often tangle with their elytra, the hardened pair of front wings that make up over half of their armor-like dorsal surface when closed.A more colorful may beetle, aka Junebug.Big Brown Bats are the only commonly encountered flying mammal remaining in the lower Susquehanna valley. To provide the nutrition and energy they need to raise young and store up reserves for hibernation, Big Brown Bats consume large quantities of night-flying scarab beetles (including Phyllophaga species) throughout the summer and fall. In addition, their survival relies in large part upon the availability of adequate summertime birthing roosts in places like warm attics. Later in the year, their needs shift to wintering sites in caves, mines, and quiet old cellars where they don’t need to share space with colonies infected by the fungus Pseudogymnoascus destructans, the pathogen that causes White-nose Syndrome (WNS), a fatal disease that has wiped out 95% of the bats in some hibernacula. (United States Fish and Wildlife Service image by Pete Pattavina)Adult Green June Beetles, also known as June Bugs, are often most evident in July. These diurnal herbivores normally consume fruit like this watermelon only after it begins rotting or has been damaged by some other animal. The larvae are mostly detrivores, specializing in consuming mold and humus, especially among the roots of plants that lie beneath layers of mulch or thatch. The grubs are preyed upon by skunks, birds, and moles.Skunks digging among grasses are often harvesting the larvae of many different species of scarab beetles.Mealworms are the commercially raised larvae of the Yellow Mealworm Beetle (Tenebrio molitor), a species of darkling beetle in the family Tenebrionidae. Perpetual pests in food storage, the grubs are now raised for research and as food for humans and insectivorous animals like this Eastern Bluebird supplementing its winter diet at our headquarters feeding station.Click beetles (Elateridae) have an articulating prothorax that snaps and propels the insect into the air as a protrusion resembling a spine “clicks” into a furrow on its ventral surface. These sudden launches can help the click beetle escape a potential predator.Like the previous individual, this click beetle was attracted to man-made light. The larvae consume small rootlets, seeds, and tubers in soil and among decaying organic matter.Another member of the click beetle family, the Eyed Elator (Alaus oculatus) mimics the head of a snake or other predator to avoid assuming the role of victim. The larvae feed among the stumps and roots of dead and dying forest trees consuming the larvae of wood-boring insects.The Six-spotted Tiger Beetle (Cicindela sexgutata) is a familiar sight on sun-dappled forest paths. It is a fast-running predator, consuming ants, spiders, and other small arthropods. The larvae ambush hunt from the entrance to their burrow, quickly snagging prey as it passes by.The aquatic larvae of the Giant Water Scavenger Beetle (Hydrophilus triangularis) are voracious predators consuming snails, other invertebrates, tadpoles, and even small fish. In some waters, they may contribute to the control of mosquitos. The adults are herbivores and scavengers. Some, like this one, are attracted to lights at night.Fireflies, also known as lightning bugs, are renowned for their ability to produce a flash of light to attract a mate on a warm summer evening. Both sexes of fireflies in the genus Photinus (seen here) produce pulses of yellow light through the chemical reaction known as bioluminescence. Their larvae feed mostly on earthworms. The genus Photuris includes the Pennsylvania Firefly (Photuris pennsylvanica), a species which is probably not particularly common in the keystone state. Photuris flashes are greenish in color and begin a bit later, usually after dark. Their larvae are scavengers, consuming fallen insects and fruits. A third genus, Pyractomena, flashes amber light. Its larvae consume snails and can be seen ascending vegetation above damp soil along quiet segments of the lower Susquehanna River at nightfall. Want to see more fireflies around your place next summer? Skip the the lawn treatments and let more space rewild to tall, mature grass and herbaceous growth, turn out the lights, then watch the magic. The star-like twinkles of glowing beetles will be signaling, “I want to hold your hand,” throughout your private firefly refuge.
