Beetle

The group of insects that belong to the order Coleoptera is known as beetles. As of now, beetles are the largest order of insects. There are about 400,000 species of beetles that have been identified this makes about the 40% of the total species of insects. According to the study done in the year 2015, four independent estimations of the beetle species number and gave a surprisingly narrow range which is about 1.5 million beetle species. These are found majorly in all the habitats that include coastal and freshwater habitats, vegetative foliage, from tree barks, leaves, flowers, and near roots. It is also found inside the galls of the plant, dead and decaying matters. The large and diverse fauna of the beetles is majorly found in the tropical forest canopies. 

The heaviest beetle found is the larva stage of the goliath beetle whereas the longest beetle is Hercules beetles. These typically have a hard exoskeleton that includes elytra. Some of the species such as rove beetles consist of short elytra and the blister beetles consist of softer elytra. The general anatomy is quite uniform even though there are several adaptations in water beetles, they trap the water bubbles under the elytra and use them while diving. They are capable of undergoing complete metamorphosis along with the series of changes in the body structure in between the hatching and the adult stage. They are bright in colors and the different patterns found on the beetles provide warning about the toxicity. 

What is a Beetle Taxonomic Classification?

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Coleoptera - It is the largest order of the class Insecta with about 250,000 described species. Obviously, with this many species, there's a good range of diversity during this order with reference to size, morphological characters, biology, and behavior. However, the order is usually characterized by a pair of elytra means hardened front wings and a pair of membranous hind wings. They have chewing mouthparts that will be slightly modified for various functions and undergo complete metamorphosis. Beetles occur in nearly every sort of habitat, from the desert to aquatic systems, and prey on various plant and animal materials.

This taxonomic order name Coleoptera is derived from the Greek word “koleopteros” and it was given to the group of elytra by Aristotle. This English name beetle is obtained from the old English name “bitelia” it is related to the word bitan which means to bite. There is another old English name “ceafor”. 

Types of Beetles

1. Ladybird Beetle: These are commonly called ladybugs. They are small and have polka dots; these are the natural pest controllers. They feed on other insects that are harmful to the crops, orchards, or the ones that threaten gardens.

2. Cockchafers: Also known as doodlebugs or may bug, cockchafers are easily identified by the distinctive "leaves" protruding from their antennae. These flamboyantly coiffed beetles once existed in great numbers throughout Europe, and their voracious appetites made them a standard agricultural nuisance. 

3. Jewel Beetles: Named for their iridescent exteriors, jewel beetles are without a doubt some of the world's most beautiful Coleoptera. The glossy, hardened, and shade-shifting forewings of those wood-boring insects have an extended history of getting used for jewelry, embroidered textiles, and other decorative arts. The most common examples of the ancient craft of "beetle wings" can be found in Asian countries like China, Japan, India, Thailand, and Myanmar.

4. Colorado Potato Beetles: The brilliant orange-yellow hue and ornamental stripes and spots of the Colorado potato beetle its status together of the foremost notorious pests of the potato plant. Over the past century, farmers have tried all sorts of pesticides to combat the beetles' voracious appetites, but due to their ability to rapidly build up resistance to chemicals, nearly all major insecticides have proven ineffective against them.

5. Giraffe Weevils: Endemic to Madagascar, giraffe weevils are named for his or her elongated necks, evolved for fighting and building elaborate nests. They are a sexually dimorphic species, meaning males and females exhibit different physical characteristics besides their sexual organs. A male's neck is double or triple the dimensions of a female's, the San Francisco Zoo says. Both sexes have those characteristic bright red elytra.

6. Golden Tortoise Beetles: There are two sorts of golden tortoise beetle: Charidotella sexpunctata and Aspidimorpha sanctaecrucis. The former is native to America while the latter is taken into account an Old World species, endemic to Southeast Asia. Both have unique tortoise shell-shaped, two-toned elytra, partially colored an excellent metallic gold and partially transparent with spots. Its regal hue has earned it the nickname "gold bug”.

7. Tiger Beetles: Tiger beetles are an outsized group of beetles of about 2,600 insects sharing the Cicindelinae subfamily. They are distinguished by their bulging eyes and long, spindly legs, which allow some like the Australian tiger beetle to run up to 5.6 mph. It is, therefore, the fastest known insect within the world.

8. Namib Desert Beetles: While it's going to appear as an unspecified beetle, the Namib Desert beetle is about a part not necessarily for its appearance, except for its unique way of collecting water. It's called fog basking. The beetle leans its body into the wind and lets water droplets from the damp air accumulate on its legs, then travel down its body into its mouth. Scientists inspired by the hydrophilic properties of the beetle's bumpy back are developing groundbreaking technology that can harvest water from the air.

9. Flower Chafers: Flower chafers is a category of scarab beetles that structure the subfamily Cetoniinae, called so because they survive plant pollen, nectar, and fruit. They are the sole beetles within the Scarabaeidae that have a worldwide distribution. There are about 3,600 species of flower chafer, and while a variety of them exhibit brilliant, iridescent color, a number of them are more subdued in appearance.

10. Longhorn Beetles: Longhorn beetles have extremely long antennae like the huge horns of longhorn cattle. They're quite striking in their imago state, but as larvae, they can be quite invasive. The roundheaded borers, as they're also called, are experts at burrowing into the wood and destroying living trees, wooden homes, and untreated lumber. Of all 26,000 species, the rare titan beetle is one of the most important insects within the world. Known to get older to six inches long, the beetle's mandibles are powerful enough to snap a pencil in half.

11. Stag Beetles: There are about 1,200 species of stag beetle in the world and all have pincer-like mandibles. As a sexually dimorphic species, the male is provided with a group of impressive jaws that he uses to fight other males when competing for a mate. While the mandibles of a female lamellicorn beetle are notably smaller, they will still pack quite painful bites not that they are going for human flesh fairly often.

12. Dogbane Beetles: Found throughout eastern North America, dogbane beetles boast metallic elytra that shine blue-green, metallic copper, golden, and crimson as they catch the light while munching on their favourite hemp plant, dogbane. The beetle belongs to a huge family of leaf-eaters called Chrysomelidae, making it a foreign cousin of the pesky Colorado potato beetle.

Beetle Insect - External morphology

Beetle insects are generally characterized by a very hard exoskeleton and hard forewings not usable for flying. Almost all beetles have mandibles that move during a horizontal plane. The mouthparts are rarely suctorial, though they're sometimes reduced whereas the maxillae always bear palps. The antennae usually have eleven or fewer segments, except in some of the groups. The coxae of the legs are usually located recessed within a coxal cavity. The genitalic structures are found telescoped into the last abdominal segment altogether along with the extant beetles. The beetle's exoskeleton is formed from numerous plates, these plates are called sclerites, these are separated by thin sutures. This design provides armored defenses while maintaining flexibility. 

Like all the insects, beetle’s bodies are divided into three sections: 

• The top

• The thorax

• The abdomen. 

Because there are numerous species, identification is sort of difficult and relies on attributes including the form of the antennae, the tarsal formulae, and shapes of those small segments on the legs, the mouthparts, and the ventral plates such as sterna, pleura, coxae.

1. Head: The head consists of mouthparts that are projecting forward or sometimes downturned, it is usually heavily sclerotized and sometimes they are very large. They have compound eyes and are capable of displaying remarkable adaptability, as in the case of the aquatic whirligig beetles, where they are split to allow a view both above and below the waterline. The anatomical organization of the compound eyes could also be modified and depends on whether a species is primarily crepuscular, or diurnally or nocturnally active. Ocelli are found within the adult carpet bug, some rove beetles, and therefore the Derodontidae. The mandibles appear as large pincers on the front of some beetles. The mandibles are a pair of hard, often tooth-like structures that move horizontally to understand, crush, or cut food or enemies.

2. Thorax: The thorax is segmented into two discernible parts; they are the pro-thorax and ptero-thorax. The pterothorax is the fused mesothorax and meta-thorax, which are commonly separated in other insect species, although flexibly articulate from the prothorax. When viewed from below, the thorax is formed by combining all three pairs of legs and both pairs of wings that arise. In the abdomen, everything is posterior to the thorax. 

When viewed from above, most beetles appear to possess three clear sections, but this is often deceptive: 

• On the beetle's side

• The center section may be a hard plate called the pronotum, which is merely the front part of the thorax

• The beetle's wings concealed the rear part of the thorax. This further segmentation is typically best seen on the abdomen.

3. Legs: The multisegmented legs end in two to five small segments called tarsi. Like many other insect orders, beetles have claws, usually one pair, on the top of the last tarsal segment of every leg. While most beetles use their legs for walking, legs are variously adapted for other uses.

4. Wings: The forewings of beetles aren't used for flight, but form elytra which cover the hind part of the body and protect the hindwings. The elytra are usually hard shell-like structures that must be raised to permit the hind wings to maneuver for flight. However, in the soldier beetles, the elytra are soft, earning this family the name of leatherwings. Other soft wing beetles such as the net-winged beetle, have brittle wings that can be ruptured easily in order to release chemicals for the purpose of defense.

5. Abdomen: The abdomen is present behind the metathorax. These are made up of a series of rings where each of these rings consists of a hole called a spiracle that helps in respiration and breathing. It consists of three different segmented sclerites. 

Beetle Insect - Anatomy and Physiology

1. Digestive System: The gastrointestinal system of beetles is majorly adapted for a herbivorous diet. Most of the digestion takes place within the region of the anterior midgut, although in predatory groups just like the Carabidae, most digestion occurs within the crop by means of midgut enzymes. In the Elateridae, the larvae are liquid feeders that digest their food by secreting some of the enzymes. The alimentary tract basically consists of a narrow pharynx, a widened expansion, the crop, and a gizzard that is developed poorly. This is followed by the midgut, which varies in dimensions between species to species, with an outsized amount of cecum, and therefore the hindgut, with varying lengths. There are typically four to six Malpighian tubules.

2. Nervous System: In the beetles, the nervous system contains all the kinds found in insects, varying between different species, from three thoracic and seven or eight abdominal ganglia which may be distinguished to that during which all the thoracic and abdominal ganglia are fused to make a composite structure.

3. Respiratory System: Like most insects beetles can also inhale air, for the oxygen it contains, and exhale carbon dioxide, and it is traveled through a tracheal system. Air enters the body with the help of spiracles, and during a system of tracheae, air circulates within the hemocoel and tracheoles, through these walls the gases can diffuse. Diving beetles, like the Dytiscidae, carry a bubble of air with them once they dive. Such a bubble is also present under the elytra or against the body by specialized hydrophobic hairs. The bubble is capable of covering at least some of the spiracles, permitting air to enter the tracheae. The function of the bubble is not only to store air but also act as a physical gill. The air that it traps is in touch with oxygenated water, so because the animal's consumption depletes the oxygen within the bubble, more oxygen can diffuse in to replenish it. Carbon dioxide is more soluble in water than compared to oxygen or nitrogen, so it readily diffuses out faster. Nitrogen is that the most plentiful gas that is present in the bubble, and therefore the least soluble, so it constitutes a comparatively static component of the bubble and acts as a stable medium for respiratory gases to accumulate in and undergo. 

4. Circulatory System: Like other insects, beetles have open circulatory systems, with supported hemolymph instead of blood. As in other insects, in the case of beetles also a segmented tube-like heart is attached to the dorsal wall of the hemocoel to perform the circulatory functions. This heart consists of paired inlets or Ostia at intervals down its length, and circulates the hemolymph from the most cavity of the hemocoel and out through the anterior cavity in the head.

5. Specialized Organs: Different glands are specialized for various pheromones to draw the attention of the mates. Pheromones from species of Rutelinae are produced from epithelial cells lining the inner surface of the apical abdominal segments; amino acid-based pheromones of Melolonthinae are produced from eversible glands on the abdominal apex. Other species produce different types of pheromones. To attract a mate, fireflies use modified fat body cells with transparent surfaces backed with reflective uric acid crystals to produce light by bioluminescence. Light production is highly efficient, by oxidation of luciferin catalyzed by enzymes in the presence of adenosine triphosphate (ATP) and oxygen, producing oxyluciferin, carbon dioxide, and light.

6.Reproduction: The typical sort of metamorphosis in beetles passes through four main stages: the egg, the larva, the pupa, and therefore the imago or adult. The larvae are commonly called grubs and therefore the pupa sometimes is named the chrysalis. In some species, the pupa could also be enclosed during a cocoon constructed by the larva towards the top of its final instar. Some beetles, like typical members of the families Meloidae and Rhipiphoridae, go further, undergoing hypermetamorphosis during which the primary instar takes the shape of a triungulin.

Beetle Insect - Behaviour

1. Locomotion: The elytra allows beetles to perform both actions to fly and to move through confined spaces. It can be done by folding the delicate wings that are present under the elytra while not flying, and folding their wings out just before takeoff. The unfolding and folding operation of the wings are performed by muscles that are attached to the base of the wings. as long as the tension on the radial and cubital veins remain, the wings remain straight. In some day-flying species, flight does not include large amounts of the lifting of the elytra, having the metathorax wings extended under the lateral elytra margins. The altitude reached by beetles in flight varies.

2. Communication: Beetles have a spread of the way to speak, including the utilization of pheromones. The mountain pine beetle emits a pheromone to draw in other beetles to a tree. The mass of beetles is ready to overcome the chemical defenses of the tree. After the tree's defenses are exhausted, the beetles emit an anti-aggregation pheromone. This species can stridulate to speak, but others may use sound to defend themselves when attacked.

3. Feeding: Beetles are ready to exploit a good diversity of food sources available in their many habitats. Some are omnivores, eating both plants and animals. Other beetles are highly specialized in their diet. Many species of leaf beetles, longhorn beetles, and weevils are very host-specific, feeding on only one species of plant. Ground beetles and rove beetles, among others, are primarily carnivorous and catch and consume many other arthropods and little prey, like earthworms and snails.

4. Parenting care: Parental care is found in a few families of beetles, perhaps for protection against adverse conditions and predators. The beetle Bledius spectabilis lives in salt marshes, therefore the eggs and larvae are endangered by the flood tide. The maternal beetle protects the eggs and larvae, burrowing to keep them from flooding and asphyxiating and protects them from the predatory carabid beetle such as Dicheirotrichus gustavi and from the parasitoid wasp such as Barycnemis blediator, which kills some 15% of the larvae.