About 300 million years ago, insects were scales larger than they are today: a shudder-inducing thought for anyone with entomophobia. Griffinflies, for instance, were massive dragonflies with wingspans reaching 28 inches. Insects were able to reach gargantuan sizes largely because the earth's atmosphere was rich in oxygen in prehistoric times. Since then, as oxygen levels have decreased, insects' air pipes have shrunk to adapt, and their bodies along with them.
However, there are still many species around the world that have maintained impressive sizes. They are mostly found in oxygen-rich and scarcely populated areas, such as rain forests, that have allowed them to evolve without intrusion.
Stacker compiled a list of 20 of the biggest insects in the world using various news, scientific, and other sources. However, defining "biggest" can be more complicated than it seems. For instance, the insect with the largest wingspan is Queen Alexandra's birdwing, which can stretch to an entire foot in width. The longest or tallest insect would be Phyrganistria chinensis Zhao, a stick insect that can grow to 24.6 inches. The heaviest insect is the Giant wētā, weighing up to 70 grams.
By all units of measurement, beetles and moths tend to be found in larger sizes more often than other insects. Read on to find out just how big these impressive creatures can get and what that means for their diets, habitats, and defences.
Attacus atlas: Atlas moth
- Size: 11-inch wingspan
The Atlas moth is immediately recognizable for its large wingspan, which is covered in a distinct orange-and-white pattern. The largest of the moth species, it is found only in tropical forests in Asia.
Chalcosoma atlas: Atlas beetle
- Size: 5.1 inches long
Atlas larvae are notably defensive, known to bite anything that touches them, and will fight among each other to death if food is scarce. With a life span of 12 months, the species is found mostly in Indonesia.
Deinacrida heteracantha: Giant weta
- Size: 8 inches long, 2.5 ounces
The wētā derives its name from the indigenous Maori language, meaning "god of ugly things." It is endemic to New Zealand. Because the nation was void of mammals for an extended period, the wētā could evolve to a rodentlike size, though the introduction of actual rodents to the island has decimated much of its population.
Dynastes hercules: Hercules beetle
- Size: 7 inches long
The horn takes up almost half of the body length of male Hercules beetles, though females lack this appendage entirely. The species has been rumoured to be able to carry up to 850 times its body mass, though this may be closer to a still-impressive 100 times its body mass in reality.
Eacles imperialis imperialis: Imperial moth
- Size: 7 inch wingspan
Most of the imperial moth's life is dedicated to pupating, the stage in which it grows from larva to a mature adult. Because of this, it takes great care in choosing a place to settle and pupate, as it will be completely vulnerable to predators during that time. Once an adult, the moth doesn't waste any time eating, instead focusing entirely on mating before death.
Enoplocerus armillatus: Giant longhorn beetle
- Size: 5.9 inches long
This insect is spread far and wide across the South American continent, observed in Argentina, Colombia, French Guiana, Guyana, Venezuela, Trinidad and Tobago, Ecuador, Peru, Brazil, Bolivia, Paraguay, Panama, and Suriname. It is recognizable by its long black antennae and light brown wings.
Gauromydas heros: Mydas fly
- Size: 2.8 inches long, 3.9-inch wingspan
The Mydas fly's greatest defense is its ability to perform convincingly. By imitating the sting of more threatening wasps and bees, it successfully wards off predators. It is also a natural predator itself, commonly eating other flies.
Goliathus regius: Royal goliath beetle
- Size: 4 inches long, 2.5 ounces
Found across central Africa, this is the largest of all beetles, able to grow to nearly the size of a human hand. It typically nourishes itself on fruit, bark, and tree sap; it has also been raised in captivity on a diet of cat and dog food.
Lethocerus grandis, Lethocerus maximus: Giant water bug
- Size: 4.7 inches long
If you haven't heard of a giant water bug, you might be thinking of one of its many nicknames, including "toe-biters, Indian toe-biters, electric-light bugs, alligator ticks, or alligator fleas." These bugs call freshwater streams and ponds its home. They are also a popular snack in Southeast Asia.
Lucanus cervus: European stag beetle
- Size: 3 inches long
The European stag beetle has long front mandibles, which males use for both courting females and wrestling opponents. The species' population is growing smaller, partly due to over-clearing in forests.
Macrodontia cervicornis: Sabertooth longhorn beetle
- Size: 6.7 inches long
This species has extra-long mandibles, thus earning the Macrodontia prefix (translating to "long tooth"). It spends most of its life as larvae, a stage extending for up to a decade. It is found in rain forests in Ecuador, Peru, Brazil, Colombia, and Bolivia.
Macropanesthia rhinoceros: Giant burrowing cockroach
- Size: 3 inches long
These creatures are native to Australia and can weigh up to 1.2 ounces. Unlike other cockroaches, they do not have wings. They are natural composters, feeding on dead leaves.
Megasoma actaeon: Actaeon beetle
- Size: 5.3 inches long
This beetle gets its namesake from Actaeon, a hero of Greek mythology who was transformed into a stag. It can be found across South America, including in French Guiana, Guyana, Panama, Peru, Bolivia, Brazil, Suriname, Colombia, Ecuador, and Venezuela.
Megasoma elephas: Elephant beetle
- Size: 5.1 inches long
The elephant beetle can be found in the rain forests of central and South America. Males use their horns to battle others over mating partners and food supply—not by injuring, but by forcing others away.
Ornithoptera alexandrae: Queen Alexandra's birdwing
- Size: 11-inch wingspan
This species is the largest butterfly on Earth. It was named after Queen Alexandra of Britain, wife of King Edward VII, who sat on the throne at the beginning of the 20th century. It has marked sexual dimorphism, meaning males and females have very distinct appearances.
Pepsis pulszkyi: Tarantula hawk
- Size: 2.7 inches long, 4.5-inch wingspan
True to its moniker, the tarantula hawk is a wasp with the remarkable habit of eating tarantulas, despite being dominated in size by the spider. To do this, they immobilize the tarantula by stinging them, dragging them away, and consuming them whole. Perhaps unsurprisingly, the tarantula hawk also packs a punch against humans, able to deliver a painful—but nonlethal—sting.
Phryganistria chinensis: Stick insect
- Size: 25.2 inches long
The stick insect's name is the key to its natural defense system: When predators are nearby, this species camouflages itself among twigs and branches to hide. These insects can even lose (and later regenerate) limbs or play dead to further evade danger.
Tenodera sinensis: Chinese praying mantis
- Size: 7 inches long
Though this bright green insect mostly relies on other insects for nourishment, it has been observed to eat small reptiles and mammals from time to time. The species has a decently large population in the United States thanks to its eggs being commercially available to the public.
Titanus giganteus: Titan beetle
- Size: 6.6 inches long
The Titan beetle is an insect to be reckoned with: When cornered, it will make a hissing sound to ward off predators, and its jaw is strong enough to penetrate human skin if necessary. This beetle is also so large that it cannot take off through wing power alone; it needs to first launch itself off of a tree to fly.
Tropidacris: Tropidacris grasshopper
- Size: 5 inches long, 9-inch wingspan
The Tropidacris grasshopper uses colour to protect itself: Nymphs use black and yellow to ward off predators, while grown adults adopt green, yellow, and brown to camouflage themselves. It also hears via the belly: its tympanal organ, which is in the abdomen, completes this task. The antennae, on the other hand, house its sense of smell.
