Beetles of North America - Order Coleoptera
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Beetles are the dominant form of life on earth: one of every five living species is a beetle, and one fourth of all animals are beetles. Coleoptera is the largest order in the animal kingdom.
Gold and Brown Rove Beetle lateral view
Aristotle described beetles as "insects with wing cases" = Coleoptera, from Greek koleon, "sheath", and pteron, "wing."  There are about 450,000 species of beetles, representing about 40% of all known insects. Beetles live in nearly every habitat, and for every kind of food, there's probably a beetle species that eats it. Beetles first appeared during the lower Permian period, about 270 mya [5].

Along with butterflies, bees, flies, moths and some other invertebrates, beetles have the most complex form of metamorphosis, called complete metamorphosis, or holometabolous development, which includes four distinct phases: egg, larva, pupa, and adult [3].

Eggs develop in the female beetle's ovaries, and are laid in a protected place with conditions suitable for the development of the larvae, including a ready food supply. Eggs are laid singly or in masses; hatching occurs within several days. The young are left to care for themselves.

Longhorn Beetles - Family Cerambycidae
Longhorn Beetles - Family Cerambycidae contains beetles with extremely long antennae, often longer than the beetle's body. There are over 20,000 known species. Many longhorns are serious agricultural pests, as their larvae have the unfortunate habit of boring wood. The Asian Longhorn beetle, for instance has been responsible for the preventive destruction of thousands of trees in Northern Illinois and other locations in the United States and Canada.

Most Cerambycidae larvae feed within dead, dying or even decaying wood, but some taxa are able to use living plant tissue. The larvae of a few species move freely through the soil, feeding externally upon roots or tunneling up under the root crown. Most adult cerambycids, particularly the brightly colored ones feed on flowers and pollen, and as such can be important pollinators of some flowering plants. Other species consume sap, leaves, blossoms, fruit, bark or fungi.

Beetle eggs hatch into a worm-like larval stage variously called grubs, worms, and some are called borers; those being among the most destructive pests on the planet as of this writing. Several distinct larval body forms occur in Coleoptera:
  • C-Shaped, or scarabaeiform: body is distinctly curved, soft. Larvae inactive. White grubs found in turf fit this category.
  • Wormlike, or vermiform: body is round in cross-section, legless like a worm.
  • Campodeiform: larvae resemble bristletails in the genus Campodea. Many larvae of predaceous beetles are of this type.
  • Elateriform: larvae of the click beetles (Elateridae), commonly called wireworms, are elongate with a hard shell and short legs. Wireworms are destructive in a wide variety of agricultural crops, but are especially severe on corn and potatoes. Wireworms feed on the seeds, roots, and stems of their food plants [4].
  • Caterpillarlike, or eruciform: larvae of many beetles that live in the open and feed on foliage fit in this variety. Despite their resemblance to the familiar lepidopteran caterpillar, this larva does not have abdominal legs.
  • Many beetle larvae have characteristics of more than one of these forms, resulting in increased diversity and adaptability.
Beetle larvae, despite their variety of body forms, nearly all have opposable, chewing mouthparts, e.g., bark beetle larvae live in the juicy layer between the bark and wood; their tunneling kills trees by the millions, especially trees already stressed by drought and rising ambient temperatures due to human-induced climate change[2]. Bark beetle larvae are only one of the coleopteran assaults on the world's plants; Pine sawyer beetle, Asian longhorned beetle, emerald ash borer, mountain pine beetle, spruce beetles and others are wreaking havoc in forests and timberlands worldwide [2].

Beetle larvae live in a wide variety of both terrestrial and aquatic environments. Most feed on or within various parts of plants, or in vegetation in various states of decomposition, or animal carcasses; some feed on stored grain, a few feed on fungi. Many larvae are predaceous on other insects or even small animals, especially in aquatic environs. A small number are parasitic, feeding on a single individual prey [3].

The skin of the larva does not stretch to accommodate growth, so the skin is shed in the process of molting, allowing a marked increase in size. The stages marked by such molts are called instars. Some beetle larvae undergo as few as 3 instars, others as many as six. As in most invertebrates, the final instar most resembles the adult insect. After the last instar, the larva changes to the next developmental stage, the pupa.

Leaf Beetles - Family Chrysomelidae is 2nd largest among the phytophagous (plant-eating) beetles, taking a back seat only to the weevils (Family Curculionidae). There are as many as 35,000 described species and perhaps up to 60,000 total species. Presently, the Chrysomelidae are classified in 195 genera and approximately 1,720 valid species and subspecies (plus 149 Bruchinae species) accepted as occurring in North America north of Mexico. [1]

Leaf beetles feed strictly on plant materials. The adults usually consume leaves, stems, flowers, and pollen. Most larvae are subterranean in habit, feeding on roots and rootlets, but others will consume foliage as well. Many chrysomelids are very specific to particular host plants, but most are able to live on a variety of plants, e.g. the so-called dogbane leaf beetle, Chrysochus auratus, which feeds on prairie plants such as milkweed (Asclepias sp.) and plants in the dogbane genus Apocynum. [2]

Clay-Colored Leaf Beetle
Green Tiger Beetle
Ground Beetles & Tiger Beetles - Family Carabidae
Family Carabidae is one of the largest insect families with over 30,000 species worldwide. Most are shiny black, but some are brightly colored. They have a conspicuous prothorax (the wide area in front of the narrow "waist" and immediately behind the head) and long legs with spurs on the tibia.

Tiger Beetles, being a subfamily of Carabidae are naturally quite similar morphologically. The ground beetles differ in the following ways: antennae inserted above the mandibles to the side of the clypeus, and below the eyes. Most ground beetles have a head which is narrower than the pronotum.

Family Cantharidae - Soldier Beetles are soft-bodied, often brightly colored insects almost always found gathered on flowering plants. They are slow, lumbering fliers and easily caught; not surprisingly, they have chemical defenses which make up for these apparent evolutionary shortcomings.

Soldier beetles produce cantharidin, a poisonous irritant produced in paired glands in the prothorax and on each of their first eight abdominal segments. When molested, the beetle emits droplets of toxic, irritating white viscous fluid from pores along their sides.

Colorado Soldier Beetle
Orange Blister Beetle
Family Meloidae - Blister Beetles also produce cantharidin, just like their brethren the soldier beetles. Stored in the insect's blood, the compound is stable and remains toxic even in carcasses. Animals may be poisoned by ingesting beetles while grazing or eating harvested silage.

Absorbed through the intestine, this blistering agent can cause symptoms such as inflammation, colic, straining, elevated temperature, depression, increased heart rate and respiration, dehydration, sweating, and diarrhea. Cantharidin can also cause severe skin inflammation and blisters.

Click Beetles - Family Elateridae
Beetles in the family Elateridae are commonly called click beetles, elaters, skipjack, snapping, or spring beetles. They posess a mechanism by which they can violently launch temselves several inches into the air, a method they use to avoid predators and right themselves if they happen to fall on their backs. A spine on the prosternum can be snapped into a corresponding notch on the mesosternum, producing a violent "click" which can bounce the beetle into the air. There are about 7000 known species.
Scarab Beetles - Family Scarabaeidae
The ancient Eyptians worshipped a scarab beetle Scarabaeus sacer as the incarnation of their sun god, Ra. The species' habit of rolling a dung ball for use as a larval food was analogous to the sun being rolled across the sky.

 The scarab beetles' distinctive antennae are tipped with leaflike plates called lamellae, that can be drawn into a compact ball, or fanned out when sensing pheromones or aromas. The front tibia are evolved for digging. Many scarabs are scavengers that help recycle dung, carrion, and decaying plants. Others are agricultural pests (e.g., the Japanese beetle). The scarab family has about 1300 North American species.

Weevils - Family Curculionidae
Weevils, also known as snout beetles, are among the most destructive insects on the planet.  The Boll Weevil is one of the most famous of all insects, devastating the U.S. cotton crop in the 1920's, and still causing upwards of $300 million in damage each year.

There are over 35,000 species of weevil, with more than 2,500 species in the United States and Canada alone. All are strictly herbivorous. The mouthparts of snout beetles are modified into down-curved snouts, or beaks, adapted for boring into plants; the jaws are at the end of the snout. The bent antennae usually project from the middle of the snout.

Weevils - Family Curculionidae
Some beetles attack plants and stored foods, while others are beneficial as pollinators of flowering plants and predators of other insect pests. However, beetles present one of the greatest threats to our trees and forests in this age of man-made global warming. Across millions of acres in the northern and central Rocky Mountains, the pines are falling victim to beetles that were once held at bay by bitterly cold winters. As Earth's climate warms, scientists say, that control is no longer happening [1].

In the 1990s, the white spruce population of Alaska's Kenai Peninsula was wiped out by beetles [1].  A massive outbreak of pine and spruce beetles in British Columbia and Alberta is killing more healthy, adult trees than logging and wildfires combined [2]. All across the globe, our forests are stressed like never before.

While perhaps not directly related to climate change, the Asian Longhorned beetle is a newly introduced species to North America; its discovery in New York State and near Chicago, Illinois in the late 1990's necessitated the destruction of thousands of trees in order to stop its spread. The Emerald Ash Borer beetle is now in the process of munching its way through the ash trees of North America.

Fire-colored Beetle
Fire-Colored Beetle
Firefly / Lightning Bug
Firefly / Lightning Bug
Lady Beetles
All Lady Beetles
Checkered Beetle
Checkered Beetle
Stag Beetle
Stag Beetle

Net-Wing Beetle
Dung Beetle
Dung Beetle - Geotrupes
dung beetle
Dung Beetle - Copris

Clerid Beetle
 Wood-boring Beetle
Wood-Boring Beetle
Oak Borer Beetles
Oak Borer
References
  1. New York Times, October 1, 2011, "With Loss of Forests, a Loss of Key Climate Protectors"
  2. Luisanna Carrillo-Rubio, The Climate Institute, "A Threat to the World's Forests Aggravated by Climate Change"
  3. Richard E. White, Field Guide to Beetles of North America, Houghton-Mifflin 1983
  4. Wikipedia, "Beetle"
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