The World's Biggest Bugs

Before we talk about what the world's biggest bugs are, we should define exactly what we mean by the word "Bug." After all, it isn't really a scientific designation. Though often when we use the term "bugs" we mean insects, some dictionaries extend that definition to apply to any creepy crawly, critter. For our purposes we are going to define "bugs" as insects, arachnids and centipedes.

These creatures are all examples of arthropods: invertebrate animals that have an exoskeleton (external skeleton), a segmented body, and appendages with joints. In addition to the animals noted above, other creatures that would fall into the category of arthropods would be crabs, lobsters and barnacles. About 80% of all known animal species are arthropods.

Enormous Insects

Insects are the largest class of anthropods with over a million known species and probably a lot of other ones not yet discovered. Most of the heaviest and largest of the insect species fall into the order of beetles. Beetles are different from other winged insects because they have a front pair of wings that are hard and thick. This front pair of wings act as a protective cover for the back pair of wings which are fragile and folded underneath. A ladybug is a common example of a beetle.

There are several different species of beetle that vie for the honor of being the largest. The Goliath beetle (found in the rainforests of Africa) have been known to grow up to 4½ inches in length (11.5 cm) and weigh 3.8 oz (100g) in their larval stage. Goliath beetles primarily feed on tree sap and fruit. Like all beetles, Goliaths start as eggs laid by their mother which hatch into larva. The larva, after feeding and growing, eventually form a pupa. Inside this protective covering the beetle grows, changes and eventually emerges in its adult form.

Another huge beetle is the Hercules beetle (Dynastes hercules) which lives in the rainforests of Central America, South America, and the Lesser Antilles They have been known to grow up to 6 ½ inches in length (17cm) but most of their length can be attributed to an enormous horn the male carries. Because of this, the Hercules is actually much lighter that the Goliath. A third beetle that is considered amoung the biggest is the Titan beetle (Titanus giganteus) which is native to South American tropics. At 4½ inches, its length is very similar to that of the Goliath.

While beetles seem to have won the contest for the heaviest insects, they aren't the longest by far. Stick insects are an order of insects that camouflage themselves using cylindrical stick-like bodies or flattened, leaflike shapes. One species, Phobaeticus chani or Chan's megastick, can have a body length of 14.1 inches (35.7cm). With their legs extended, a megastick can measure a whopping 22.3 inches (56.7cm) in length. Little is known about this strange species as it was only discovered in 2008. So far only a handful have been found. These ultra-long insects are native to the island of Borneo in Asia, though smaller species of walking sticks can be found around the world.

While they are lightweights compared to beetles and even Chan's megastick, butterflies and moths can grow to some impressive sizes if you consider their wingspans. Atlas moths (Attacus atlas), which are found in the forests of Southeast Asia and the Malay archipelago, can have wingspans 10 inches across (25cm). There are two stories about how the Atlas got its name. First is that the name comes from the giant Atlas, a titan of Greek mythology. The second is that the color pattern on their wings looks like a map or atlas. In Cantonese (a form of Chinese spoken in Southern China) the name means "snake's head moth", which refers to the odd shape and color pattern of the forewing, which looks like a snake's head.

The largest butterfly in the world is the Queen Alexandra's Birdwing which lives in the forests of Oro Province in eastern Papua New Guinea. It has a wingspan of up to 12.2 inches (31cm) and a body length of 3.2 inches (8cm). Like the Atlas moth, the female of the species is larger and heavier than the male. The Queen Alexandra's Birdwing is considered an endangered species because it has such a small natural habitat -only about 39 square miles (100km).

Oversized Arachnids

Most people consider spiders scary even if they are only a fraction of an inch across. However, spiders that are really dangerous to humans are rare (in North America there are only two species, the brown recluse and the black widow). Spiders do not feed on human blood and only bite people when they feel threatened. With only one known exception, spiders are carnivorous, but what they like to eat are mostly unwanted insects. They particularly like mosquitoes which is one reason to be kind to a spider next time you see one.

The largest spider in the world is the Giant Huntsman spider (Heteropoda maxima). This spider has a leg span of 12 inches (30cm) and a body length of 1.8 inches (4.6cm). It lives in Laos in Southeast Asia. Because of its coloration, a pale yellowish-brown, scientists think that it lives near the entrances of caves.

The Giant Huntsman spider was only discovered in 2001. Before that the record holder was the Goliath Birdeater (Theraphosa blondi) of rain forests in northern South America. It can have a leg span of almost 12 inches and weigh an enormous 6.0 ounces (170g) which makes it the heavier of the two species. The Goliath is a member of the tarantula family of spiders and despite its name, eats mostly insects and other invertebrates. Occasionally, however, they have been known to dine on frogs, lizards, bats, and even venomous snakes. The Goliath is the largest of the 900 species of tarantula spiders that live in almost every part of the world except Antarctica. Though tarantulas have a venomous bite, it is rarely fatal to humans.

Though not as big as these spiders, another large and interesting arachnid is the Heterometrus swammerdami, a scorpion in India that grows up to 11 ½ inches in length (29.2cm) and can weigh 2.1 ounces (60g). Fortunately, this type of scorpion isn't very venomous. In fact it actually kills its prey by crushing it with its pincers rather than stinging it.

Supersized Centipedes

The last group on our list is centipedes. The name comes from the Latin prefix centi which means "hundred", and pes, which means "foot". The actual number of legs a centipede has, however, varies with the species. Some have as few as twenty, others up to around three hundred. There are estimated to be around 8,000 different species of centipedes in the world. They prefer to live in moist environments as they easily lose water through their skin.

The species which is the largest is Scolopendra gigantea, the Peruvian giant yellow-leg centipede (also known as the Amazonian giant centipede). It's native to northern South America and can grow up to 12 inches (30cm) in length with either 21 or 23 pairs of legs. (For some unknown reason all centipedes always have an odd number of pairs of legs, never an even number). These creatures are carnivorous, very aggressive and will feed on almost everything they encounter including insects, tarantulas and also vertebrates like lizards, frogs, snakes, birds, mice, and bats. Like all centipedes, it can inject its victim with venom using pincer-like appendages which are actually a pair of modified legs. Fortunately, while the sting will give most people severe pain, fever, swelling and chills, it usually isn't fatal unless the victim happens to be allergic.

Prehistoric Big Bugs

While most of the creatures above are impressive, they pale in comparison to their pre-historic counterparts. Meganeuropsis permiana, the biggest known insect that ever lived, was a dragon fly that thrived during the Permian period from 290 million to 248 million years ago. It had a wingspan of 28 inches (71cm) and a body of almost 17 inches (43cm). Pulmonoscorpius kirktonensis was a scorpion that lived in Scotland about 340 million years ago and was 28 inches long (70cm). Another ocean-going version of scorpion, Brontoscorpio anglicus, wsa found fossilized in sandstone from Trimpley, Worcestershire, England and was a whopping 3.3 feet (1m) in length. Finally, there was Euphoberia which an extinct form of either millipede, or centipede (scientists can't decide which) that lived in Europe and North America. In either case, you wouldn't want to meet one if it were alive today. It was over three feet in length (1m).

Why were some bugs bigger back in the old days? Insects don't have lungs but get the oxygen they need from the air to their cells through a set of hollow tubes (referred to as "tracheal tubes"). These need to get proportionally bigger as the insect does in order for the insect to get the oxygen it needs. The theory is that at some point the tubes get so large that they no longer efficiently move oxygen and limit the size of the insect. In prehistoric times, however, oxygen levels in the air, which are about 21 percent today, were as high as 31 percent, allowing the insects to grow larger even though they had the same sized tubes. Scientists have found that some modern insects (particularly dragonflies) grow larger when reared in artificial environments with high levels of oxygen.

The evolution of birds may also account for smaller insects. Once birds that ate insects arrived on the scene around 150 million years ago, flying insects had to become faster and more maneuverable, which usually means being smaller, to avoid becoming an avian lunch.

A Partial Bibliography

Jesús Molinari, Eliécer E. Gutiérrez, Antonio A. de Ascenção, Jafet M. Nassar, Alexis Arends & Robert J. Márquez Predation by giant centipedes, Scolopendra gigantea, on three species of bats in a Venezuelan cave, Caribbean Journal of Science 4 (2) 2005.

Why Were Prehistoric Insects Huge? Science Daily www.sciencedaily.com August 2007.

World's Longest Insect Revealed, Natural History Museum www.nhm.ac.uk October 16, 2008.

Erik N. Kjellesvig-Waering Brontoscorpio anglicus: A Gigantic Lower Paleozoic Scorpion from Central England, Journal of Paleontology 46.