Beetle

Beetles belong to the family of insects of the Coleoptera order, the largest among all orders having approximately 4,00,000 species.  Their hardened forewings distinguish them from a host of other insects. They have been famous since time immemorial, used for gambling and entertainment, and even kept as pets. They are the most prevalent type of insects found worldwide, occurring in land and also water.

Appearance and Physical Description

Size: Their size varies from one species to the other. The smallest is less than 1 mm, while the more significant kinds could have a length of 6 inches.

Weight: They also differ from each other when it comes to weight. The male goliath beetles weigh between 2.5 and 3.5 oz. On the other hand, the elephant beetles are 1.8 oz.

Color: They can camouflage, mostly due to the structural coloration present in them. Beetles come in bright shades of green, blue, violet, gold, red, and copper.

Head: Beetles have a large and hard head, comprising mouthparts projecting in front or at times turned in the downward direction. The antennae, mouth, and eyes are located on their heads.

Eyes: Beetles have compound eyes, located in the front part of their head, giving them a distinct vision. The pattern and size, however, differs from one species to the other. Certain longhorn beetles, weevil, and fireflies possess divided eyes, helping them to see above as well as below the waterline. Some even have ocelli (single-lensed eyes that are small and simple) at the rare end of their head, which is mostly seen in the larvae.

Wings: Their forewings are not used for flight and are formed into a hard-shelled structure, elytron, shielding the hindwings. On the other hand, their hindwings, which remain within the elytra at rest, are used while flying. When the beetle prepares for flight, the thin wings emerge from the elytra. The soldier beetles have soft elytra, earning them the name leatherwings. Net-winged beetles have highly brittle wings, which can easily rupture when they try releasing chemicals for defending themselves.

Thorax: The thorax is segmented, and when seen from below, it seems as if the wings and legs are rising from it.

Legs: The adult species possess six legs, with each of the thorax segments having a pair each. The last section of the legs has a claw.

Abdomen: A host of rings make up the abdomen, each having a hole known as a spiracle, facilitating in respiration. The spiracle has three segments, namely the pleura, tergum, and sternum. The tergum is soft and membranous, hidden within the elytra and wings when the beetles are not flying. The pleura also remains concealed, while the sternum is the abdomen’s most visible part.

Distribution

Most of the beetle species have a wide distribution located in almost every continent except Antarctica. The goliath beetles occur in the tropical forests of Africa. In contrast, the Hercules beetles thrive in the Central American rainforests alongside the Lesser Antilles and South America. The elephant beetles, on the other hand, exist in South and Central America as well as Mexico.

Where Do Beetles Live

 The beetles have a diverse habitat, found in coastal and freshwater regions. They even dwell in moist and dark places, under leaves, rocks, and logs, as well as in gardens, ponds, lakes, and grain fields. Adults of certain species often dig burrows in the soil for laying eggs.

How Long Do Beetles Live

The lifespan of a beetle differs ranging from a few weeks to years. The carpet beetles live for 13 to 44 days, while the Eastern Hercules beetle survives for 3 to 6 months.

What Do They Eat

Beetles eat various types of food like the seeds, fruits, or leaves of plants, as well as small animals, preyed upon by few species. Some of them even feed on fungus growing along with the litter of leaves and even dung. The diet of the larvae differs from that of the adults.

Behavioral Characteristics

• They are versatile, and adjusting, adapting to diverse environmental conditions.
• Beetles communicate with one another in several ways, like using pheromones (secretion of a chemical factor for triggering a social response). For instance, the mountain pine beetle takes the help of a pheromone for attracting other members to a tree.
• Certain species show great parental care protecting their young ones from predators and any adverse conditions. However, some of them do not care much for their young ones after the eggs are laid. 
• Cooperative brood care exists in certain beetle species, with the larvae often feeding on the adult’s semi-digested feces.  

Adaptation

• They can balance themselves while moving because of how they walk. Their fore and hind leg remain on one side and the middle legs on the other, creating a tripod. The formation of a new tripod occurs each time they walk, making their movement smooth and efficient.
• The elytra help them to move and fly about through confined or limited areas.
• They can fold and unfold their wings flexibly because of the muscles present at the base of their wings.
• Certain species like the rove beetles have strong abdominal muscles and a soft body stature that help them pass through minute cracks with ease.
• Due to their structured coloration, beetles can camouflage well to protect themselves from predators. The avocado weevil resembles a bird’s dung, whereas, those dwelling in sandy conditions blend into the coloration of their habitat. Long-horned beetles with their yellow and black flashy bodies often mimic yellow jackets and paper wasps, giving the impression of being highly dangerous.
• They are also capable of mimicry, with some of them behaving like wasps with which they already bear a striking similarity.
• Chemical defense is another way of beetle to fight against their predators. They have special glands for producing chemicals which they eject as a mode of defense for shielding themselves against any potential danger.
• Through the mechanism of stridulation, which involves producing sound by rubbing certain parts of their body together, certain species can startle or confuse their enemy.

Life Cycle of a Beetle

The life cycle of a beetle comprises of four stages, namely the egg, larva, pupa, and adult.

The small-sized eggs are white or yellow, deposited among rotten wood, animal feces, or decayed leaves. They mostly have a smooth surface with a soft structure, though eggs of the Cupedidae family are hard.

The larvae are voracious eaters, having a worm-like appearance. Some like the leaf beetle species feed on plants; a few eat the timber’s cellulose structure while some beetle larvae like the weevils are internal feeders. The larvae stage varies from one beetle species to the other, sometimes even lasting for many years.  As they start growing, the larvae pass through the molting phase that may occur about seven to ten times before they transcend into the pupal stage.

The larva forms the cocoon in the next stage and mostly remains dormant. This phase is crucial, as the larvae gradually grow into an adult beetle. The time they take to develop may vary from about 30 days to 2 or 3 years. On stepping into adulthood, the matured beetle comes out of the cocoon, starting a new life cycle afresh.

The final stage of a beetle’s life is the adult phase, with its longevity spanning from a few weeks to many years. Certain wood-boring beetle species live for a long time.

Reproduction and Mating

Beetles have a host of mating behaviors, one of them being, reaching out to one another through pheromone communication. The male and female beetles may stridulate or even interact with each other by vibrating the objects that they sit on. Different families or genera have varied mating techniques. In fact, in the Meloidae family, the male climbs upon the female’s dorsum, stroking her palp, antennae, and head with his antennae. Competition plays a prominent role in the mating rituals of most beetles. Males are mostly territorial, fighting vigorously with one another to prevent other intruders from coming into their space. Post mating the males go away and do not play any role in bringing up their offsprings.

Are Beetles Endangered  

The ICUN marks approximately 72 of the beetle species as endangered. Some of the common reasons for their depleting numbers include loss of habitat, pollution, and diseases.  Efforts are on for conserving the population, though awareness should come from humans who must make a conscious effort of not using these insects for trade or entertainment or even as a common food source.

Beetle- FAQs

1. Can all beetles fly?

No, do they have elytra and wings, all beetles cannot fly. Ground beetles and certain weevil species have lost their flying ability. The tansy beetle is also incapable of flight, often walking between habitats.

2. Which beetles are poisonous?

Though the bites of beetles are uncommon, some of them like the blister and lady beetles release toxic substances that may prove harmful to animals.

3. Do beetles have pincers?

No, but the mandibles in front of their mouth resemble large pincers.

4. Are beetles carnivorous?

Some like the scarab beetles are carnivorous.

5. What is a group of beetles called?

A colony

6. How do beetles communicate?

They communicate through vibrations or even through sounds produced by rubbing the bodies using their legs.

Interesting Facts

• Titanus giganteus belonging to the Cerambycidae family indigenous to South America is the world’s largest beetle.
• Certain species like the scarab beetle have been highly revered in the Egyptian culture.
• About 344 beetle species are consumed as food, particularly when in the larval stage. The commonly eaten species include the rhinoceros and darkling beetle.
• These insects form an integral part of folk medicine used for treating several disorders and illnesses.
• The territorial insects of several species of male beetles are channelized well, and many countries like China use them for entertainment sports as well as gambling.
• Beetle collecting became immensely popular during the Victorian period. Alfred Russel Wallace collected about 83,200 beetles as described in his book in the year 1869.