Coleoptera Families 1
Scarabaeidae: scarab beetles
Biology and Behavior: Scarab beetles, chafers, or just scarabs, comprise a hugely-diverse family with over 30,000 species worldwide. Many are familiar to us including junebugs, may beetles, Japanese beetles, rhinoceros beetles and dung beetles (among many others). Indeed, some scarabs were considered sacred (particularly dung beetles) by the ancient Egyptians and many today are prized for their sporting abilities, especially in male vs. male wrestling matches in Asia. Among beetles, scarabs seem to hold a special place in the hearts of many insect enthusiasts, probably because they come in many different forms and have some interesting lifestyles. Most feed on decaying matter as larvae, such as rotting wood and other debris. However, larvae may feed on other sources including dung (i.e., dung beetles), living plant roots (e.g., white grubs), fungi and, sometimes, other insects (e.g., Cremastocheilus that live in ant nests and feed on the ant larvae). Most larvae are inconspicuous, living underground or hidden in logs and such. Adults are often good diggers, having powerful front legs. There are many adults, though, that are at home on flowers, and a major subfamily (Cetoniinae [1]) are even generally called flower chafers. Adult scarabs are often attracted to lights and sometimes fly at peoples' house windows (resulting in a loud THUD) to get at the lights inside. Dung beetles (mostly Scarabaeinae [2]) make up a huge group known for their use of a strange resource - dung - but also because of the ways in which they handle their food choice such as rolling balls, or building elaborate burrows and dung balls on which their young feed. Dung beetles are also known for being good parents, some being monogamous and others only lay a few eggs in their lifetime (taking more care for their offspring's survival than most insects).
Economic Importance: Scarabs are economically important in many ways. Common pests include masked chafers (Cyclocephala spp.; right), June bugs (e.g., Cotinis sp. [3] and other "June bugs"), May beetles (many species and genera [4]), and others that do not have common names. Scarabs feed on a wide range of plants. Some are pests of turfgrass, crops, ornamentals, and/or small trees, usually damaging these commodities by feeding on their roots. Several species or groups are important in this way, and are usually called white grubs. Adults of some species (e.g., Japanes beetles, Popillia japonica) also feed on the leaves and flowers of plants, including popular ornamentals like roses and trees. Other scarabs are known to also feed on damaged or ripe fruit with thin skin. Despite some being pests, many scarabs are in fact beneficial. Dung beetles are highly important for decomposing the feces of many animals, especially the dung of large herbivores including many of our livestock. Through their actions dung beetles bury large amounts of nutrient-rich dung, reduce the number of pest flies and worms that can breed in dung, and help to churn and aerate soils like earthworms. Without their impact, we would have acres upon acres of land covered in dried animal feces. Additionally beneficial scarabs include flower chafers that regularly visit flowers and probably help to pollinate plants.
How to identify Scarabaeidae: Scarabs range in size from 1-175 mm (<1/16 inch-7 inches), but most in the US are 10-30mm. Most have a typical beetle appearance, with thick elytra and usually being quite bulky relative to their size. Though many are dull brown or black, quite a few are brightly colored and/or patterned.
Some are extremely metallic, especially species of Chrysina which appear to be made of gold or silver [5]! Many scarabs are also well known for their horns (e.g., rhinoceros beetles and many dung beetles), which can grow from their clypeus (the "top lip"), head or pronotum, almost always in the males. The main characteristic of scarab beetles is their lamellate antennae (see pics;right), where the segments near the tip (last 3-7) are flattened and form a moveable club, like fingers being spread and closed. They often have thick, spiny legs (especially their front legs) with large claws and a 5-5-5 tarsal formula. The common subfamilies in the US are fairly easy to identify using a few particular traits, though to list them would be out of the scope of this page. Larval scarabs are typical "grubs", being c-shaped and pale with a dark, hardened head. They also have a blunt abdomen tip and c-shaped spiracles down the side of the body. Different groups of scarab larvae can be identified using body shape, mouthpart characteristics and features on the tip of the abdomen.
Links & References:
Scarab Central at University of Nebraska
The Scarab Beetles of Florida, Robert Woodruff, Florida Department of Agriculture and Consumer Services, 1973
The scarab beetles of Nebraska, Brett Ratcliffe, University of Nebraska State Museum, 1991
Scarab beetles (Coleoptera: Scarabaeidae) of South Carolina, Phillip J. Harpootlian, Clemson University Public Service, 2001
Buprestidae: jewel beetles or flat-head borers
Biology and Behavior: Jewel beetles (also called metallic wood borers or flat-head borers) are among the most beautiful insects and comprise a family of over 15,000 species worldwide. As their name suggests, many are often metallic and/or brightly colored, and many species are popular with collectors (sometimes being sold on the black market), or artists and jewelers. They are even considered money in some cultures. Larvae of all species feed on plants. Many feed on dead or dying trees (even into late decay) and may burrow just under the bark or further into the wood. Some species mine leaves and stems of plants, including grasses and other herbaceous types; a few will even create galls on plants. Adult jewel beetles also feed, usually on their host plant's leaves or on flowers, but some feed on fungus. Though jewel beetles can be good fliers, others prefer to play dead when confronted, tucking their legs close to their body. Some species take advantage of trees killed by wild fires and even have specialized sensors to find these heat sources in nature. Under certain conditions, larvae are known to survive for decades (perhaps up to 50 years!) inside wood - even emerging from furniture in people's houses!
Economic Importance: Jewel beetles are usually interested in dead or dying trees, but many species will attack apparently healthy trees. These species can become important forest, orchard and nursery pests. For example, the infamous emerald ash borer (Agrilus planipennis [6]) has recently invaded the US killing off ash trees (50-100 million estimated so far) across the northcentral states and neighboring Canada. Other jewel beetles may mine leaves and stems of plants as larvae, causing aesthetic damage or destroying plants altogether. While there are many species that damage plants we are interested in, some are important pollinators. Adults often visit flowers and some fuzzy ones become covered in pollen, transferring it to other flowers in subsequent visits.
How to identify Buprestidae: Jewel beetles range in size from 3-100 mm long, though most are only a centimeter or two. They are usually metallic, brightly-colored, or both. Their metallic colors are often silvery or bronze, but some are brilliant greens, blues, purples or reds (right). When they are patterned they often have yellow spots. Some are thickly covered in hairs or scales that may be arranged in tufts. As far as physical appearance, most are extremely hardened, tear drop- or bullet-shaped (pointed toward end of abdomen) beetles with a pronotum that is equal (or almost equal) in width to the abdomen and head. Their head is usually round and held flat against the prothorax (looking like it has no neck) and has large eyes. Unlike longhorn beetles, jewel beetles have short antennae, at most reaching the base of the elytra. Their antennae are often weakly serrate, but may be pectinate. Larval Buprestidae are elongate, pale, grub-like beetles that lack legs and have a conspicuously-enlarged anterior region (head plus thorax) that is also quite flattened - hence the name flat-head borers (right).
Links & References:
Elateridae: click beetles or wireworms
Biology and Behavior: Click beetles represent a commonly-encountered family of beetles with over 9,000 species worldwide. They get their name from the ability of adults to snap their body up and down (making a "click" sound), to scare enemies or right themselves when flipped over. They do this using a mechanism on the underside of their body (sternum) consisting of a small, spine-like process that fits into a locking area; the mechanism snaps in and out causing the body to quickly flex. When they flip themselves into the air they sustain some of the most powerful g-forces in nature. Biologically, click beetles are fairly diverse. Larvae of many are found in rotting wood or in the soil, where they feed on decaying materials. Many are predators, while others feed on plants, usually on the roots, tubers and freshly-planted or germinating seeds. Adult click beetles may feed on plant tissue, including leaves and flowers, but may also scavenge spores and other materials on leaf surfaces; some adults do not feed. Elateridae is one of three beetle families that include members capable of producing light (bioluminescence). Adults of some species have a spot on each side of their pronotum that glows [7], and their larvae may also glow (some even attracting prey with the light [8]). Lastly, some species like the eyed click beetle (Alaus oculatus [9]) are large and have menacing-looking eye spots to scare enemies.
Economic Importance: While some larvae may be beneficial by preying on wood-boring larvae (such as Cerambycidae and Buprestidae), most of the economically important species of click beetles are those that attack crops. These include what are familiarly known as wireworms, named because of their elongate appearance. Wireworms live in the soil and move around easily in search of food. When abundant, they can consume or damage large amounts of commodities such as potatoes, sweet potatoes, turfgrasses, corn, onion, and many other crops. They are especially damaging when they attack young plants and almost always do so through feeding on the roots and seedlings.
How to identify Elateridae: Click beetles range in size from 1-60mm, though they are generally about 15mm long. Adults are often a shade brown, but some have patterns, iridescence, and/or colors (usually red, orange, or yellow). Many are covered in coarse hairs and some even have scales. Click beetles are fairly similar in appearance across species: they are cigar-shaped, somewhat flattened, blunt near the head and pointed toward the tip of the elytra (sometimes with points). Their pronotum is diagnostic, being somewhat-humped and extending to a point at the hind corners (easily seen from above; see right). Their heads are small with large eyes, and they have moderately-long antennae that can be filiform, serrate or even pectinate. The clicking mechanism described above is also characteristic for the family, though a few closely-related families have small mechanisms (including false click beetles, Eucnemidae, that are very similar in appearance). Adults also have a 5-5-5 tarsal formula. Larvae (right) have moderately-developed legs, are elongate to extremely elongate, shiny, and reddish-brown or cream-colored. They have long mandibles and a distinct head that is often conical from the side and wide from above (having a sharp clypeus or upper lip). The tip of the abdomen of wireworms is variable (often used for identification), being blunt or with distinct spines or plates (urogomphi). They also often have a fleshy, leg-like bump on the underside of their abdomen tip.
Links & References:
Anobiidae: death-watch and spider beetles
Biology and Behavior: Death-watch beetles and spider beetles (Ptininae [10], formerly their own family) represent a diverse group with over 2,200 species worldwide. Their common names are due to some members of the former knocking inside their tunnels (sometimes in homes), a sound that was thought to foretell death; the latter beetles are so named because of their long legs and antennae, and small round body, resulting in a spider-like appearance. They are somewhat diverse in feeding habits, but are mainly associated with dead and/or dried materials. Food sources include wood and bark of dead trees, twigs, timber, woody fruits (including pine cones), seeds, fungus, galls, and sometimes living plant tissue. To feed on these tough substances, many have special microorganisms in their gut to help digest their food. Spider beetles may inhabit the nests of other animals (birds, mammals, bees and ants) where they feed on food stores, detritus and/or their host's refuse.
Economic Importance: Because death-watch beetles feed on wood and dried materials, they can become pests of human commodities and products. The most famous examples are the drug store beetle (Stegobium paniceum) and the cigarette beetle (Lasioderma serricorne) which attack stored products, tobacco, spices, and other dried goods [11]. Other anobiids may attack the structural and decorative wood of houses and wooden furniture [12]. Some spider beetles infest houses and feed off of flour, dried materials (crumbs & dead insects), and even wool.
How to identify Anobiidae: Death-watch and spider beetles are small to minute (1-9mm) beetles that are generally reddish-brown, brown or dark (black/brown). They are often dull and sculptured, or with setae all over or in patches. Some, like certain spider beetles in the genera Gibbium [13] and Mezium [14], are shiny. All are cylindrical, pill-shaped or spherical in shape. One of the best-defining features of the group is their hood-like pronotum, which covers the head (itself directed downward). Many death-watch beetles have legs that can be held tightly against their body, while spider beetles have elongate legs. All have a 5-5-5 tarsal formula. The antennae of Anobiidae come in many forms, most being 11-segmented, and either long (filiform, serrate, or pectinate) or with the last three segments elongate; some have a small club. Anobiid larvae (right) are pale, c-shaped grubs, with well developed heads much like tiny scarab larvae.
Links & References:
Death-watch and spider beetles on Bugguide
There are too many families of beetles to cover here, thus only ones of human importance are included. However, some other beetle families in this group are commonly encountered but do not usually interfere with our lives. Here is a brief synopsis of those families that are likely to be encountered, but that pose little concern to our well being.
Carabidae: ground and tiger beetles - [15] This large family of over 40,000 described species is one of the most commonly encountered by people. As their name implies, most are found running along the ground where they hunt for prey. Most have very large mandibles used to dismember their food. Some are specialized to hunt certain organisms while others are generalists. A few species are known to feed on seeds, and may become minor pests. Some are parasitic on other insects, while some are now known to specialize in attacking and feeding on amphibians. Bombardier beetles (Brachinini) are famous members of the family for producing tiny explosions by mixing chemicals out of their rear, while tiger beetles (Cicindellinae) are famous for their beautiful colors, big eyes and mandibles, and quick hunting style. Lastly, some species are known to live with ants inside the colony. Because of their diversity, they can come in various forms. However all have a 5-5-5 tarsal formula, notopleural sutures (the seams connecting the top and bottom of the prothorax), jellybean-like hind trochanters, and hind coxae that separate the first abdominal segment. In addition, most have filiform antennae and antennal cleaners on their front legs.
Staphylinidae: rove beetles - [16] Perhaps the largest family of organisms on Earth (over 60,000 described species), rove beetles are very common in nature. Most are easily distinguished from other beetle families by their shortened, leathery elytra (under which the hind wings fold) that only cover half of the abdomen. The rest of the abdomen is usually flexible and used to fold the hind wings. They also have a 5-5-5 tarsal formula. The family, however, is extremely diverse, especially since many groups that were once thought to be different are now lumped in this family. Most species are predators, though many others feed on decaying materials and fungus. A few species are ectoparasites of fly pupae. Some are found in the nests and fur of mammals, where they are though to feed on parasites. Some are associated with water, while many can be found in decaying logs, leaf litter, under rocks or at carcasses & dung.
Lampyridae: fireflies - [17] Almost everyone is familiar with fireflies (also called lightning bugs), but few people know they are not flies or bugs, but beetles. They represent one of three families of beetles that are able to produce light (the others being Elateridae and Phengodidae). Most adults and all larvae in the family produce light, larvae doing so throughout their body while in adults the organs are restricted to the tip of the abdomen. Some adults, however, do not produce light. Larvae are predators, some specializing on slugs, snails and worms, while adults are either predators or do not feed. Fireflies generally use their flashes to warn predators (they are usually distasteful) or attract mates. However some mimic the flashes of other species to attract a meal - the unfortunate species responding to the signals! Many species flash randomly, while a few are synchronous (all individuals in an area flash in unison). Most fireflies are readily identified as such by the light organs on the tip of the abdomen. However, since not all have this feature, other characteristics are useful, including a head hidden by the front of the pronotum, usually red and black coloration, enlarged eyes in many species, and filiform, serrate or pectinate antennae.
Cantharidae: soldier beetles - [18] This family, composed of over 5,000 species worldwide, is moderately common. Adults of one of the most common species, Chauliognathus pensylvanicus (right), can often be seen mating atop goldenrod and other flowers in the late summer/early fall. Adults will feed on other small insects, but also on nectar and pollen. Those that visit flowers can be regarded as important pollinators. Larval soldier beetles are predators and are sometimes seen walking across the ground. Soldier beetles resemble fireflies, though their head is not covered by the pronotum. Many have brightly-colored bodies, often being shades of orange, red or yellow, contrasted with black; this type of coloration warns predators that they are defended by many different chemicals. Their elytra are soft and leathery (sometimes with many hairs), and they have a 5-5-5 tarsal formula. Larvae are easily recongizable due to their bodies being caterpillar-like and velvety in appearance.
Other beetle pages:
Coleoptera: Introduction
Coleoptera Families 2: powder-post beetles, sap beetles, ladybugs, and relatives
Coleoptera Families 3: leaf beetles, longhorn beetles, weevils, and relatives
