Insects, which are a type of arthropod, are easily the most numerous group of organisms on the planet, with about a million species identified so far.
The title of heaviest insect in the world has many rivals, the most frequently-crowned of which is the larval stage of the goliath beetle (Goliathus goliatus), the top size of which is at least 115 g (4.1 oz) and 11.5 cm (4.5 in).
The largest confirmed weight of an adult insect is 71 grams for a giant weta (Deinacrida heteracantha), although it is likely one of the elephant beetles (Megasoma elephas & Megasoma actaeon) or goliath beetles, both of which can commonly exceed 50 g (3 oz) and 10 cm (4 in), can reach a higher weight.
The longest insects are the stick insects, see below.
Representatives of the extinct dragonfly-like order Protodonata such as the Carboniferous Meganeura monyi and the Permian Meganeuropsis permiana are the largest insect species ever known. These creatures had a wingspan of some 70 cm (28 in) and a body weight of over 452 g (1 lb), making them about the size of a crow.
- Cockroaches (Blattodea). The largest cockroach is the giant burrowing cockroach (Macropanesthia rhinoceros). This species can attain a length of 8.3 cm (3.3 in) and a weight of 36 g (1.3 oz).
- Beetles (Coleoptera). The beetles are the largest order of organisms on earth, with about 350,000 species so far identified. The true largest species are the Goliathus, Megasoma and Titanus beetles already mentioned. However, the longest-bodied species is the Hercules beetle (Dynastes hercules), reaching a maximum size of at least 19 cm (7.5 in). Much of the length is comprised of the antennae, and the top weight is 85 g (3 oz), about an ounce less than the bulkier beetles.
- Earwigs (Dermaptera). The largest of the earwigs is the St. Helena earwig (Labidura herculeana), which is up to 8.4 cm (3.3 in) in length.
- True flies (Diptera). The largest species of this huge order is the species Mydas heroes, which can reach a length of 6 cm (2.4 in) and a wingspan of 10 cm (4 in). Species of crane fly, the largest of which is Holorusia brobdignagius, can attain a length of 23 cm (9 in), but are extremely slender and are handily outweighed by Mydas.
- Mayflies (Ephemeroptera). The largest mayflies are members of the Proboscidoplocia genus from Madagascar. These insects can reach a length of 5 cm (2 in).
- True bugs (Hemiptera). The largest species of this diverse, huge order is the giant water bug (Lethocerus maximus). This species can attain a size of 11.6 cm (4.6 in), although it is more slender and thus less heavy than most other insects who reach such a size (principally the huge beetles).
- Ants & allies (Hymenoptera). The absolute largest of the ants, and the heaviest species of the order, is the females of Dorylus helvolus, reaching a size of 5 cm (2 in). The ant that averages the largest for the mean size of the whole colony is Dinoponera gigantea, averaging up to 3.3 cm (1.3 in). The largest of the bee species, also in the Hymenoptera order, is Megachile pluto, the females of which can be 3.8 cm (1.5 in) long, with a 6.3 cm (2.5 in) wingspan. Meanwhile, the largest of the wasp is probably the so-called tarantula hawk species Pepsis pulszkyi, at up to 6.8 cm (2.8 in) long and an 11.6 cm (4.6 in) wingspan, although many other Pepsis approach a similar size.
- Termites (Isoptera). The largest of the termites is the African species Macrotermes bellicosus. The huge larvae of this species can attain a size of 10.6 cm (4.2 in) and 5.5 cm (2.2 in) wide; the adults, on the other hand, don't exceed about a third of the size of the larvae.
- Moths & allies (Lepidoptera). The largest species is probably either the Queen Alexandra's birdwing (Ornithoptera alexandrae), a butterfly, or the Atlas moth (Attacus atlas), a moth. Both of these species can exceed a length of 8 cm (3.2 in), a wingspan of 28 cm (11 in) and a weight of 12 g. Their larvae can weigh up to 58 g (1.9 oz). However, the White Witch (Thysania agrippina) has the longest recorded wingspan of the order, and indeed of any living insect, at up to at least 30 cm (12 in). The white witch is exceeded in surface area and mass by both Ornithoptera and Attacus.
- Praying mantises (Mantodea). The largest species of this order is the Chinese mantis (Tenodera aridifolia). The females of this species can attain a length of up to 10.6 cm (4.2 in).
- Dragonflies (Odonata). The largest living species of dragonfly is Megaloprepus caeruleata, attaining a size of as much as 19 cm (7.5 in) across the wings and a body length of over 12 cm (4.7 in).
- Grasshoppers & allies (Orthoptera). The largest of this widespread, varied complex of insects is the giant weta (Deinacrida heteracantha) of New Zealand. This formidable insect can weigh over 75 g (2.6 oz) and measure up to nearly 10 cm (4 in), rivaling the huge beetles in size.
- Stick insects (Phasmatodea). The largest stick insect and the longest-bodied insect in the world is the giant stick insect (Phobaeticus kirbyi). The body alone measures up to 30 cm (12 in), while the overall length (from the hind to the front legs) is up to 51 cm (20 in), and the body weight is up to 72 g (2.5 oz).
- Stoneflies (Plecoptera). The largest species of stonefly is Pteronarcys californica, a species favored by fishermen for use. This species can attain a length of 5 cm (2 in) and a wingspan of nearly 7.5 cm (3 in).
- Booklice (Psocoptera). The largest of this order of very small insects are the barklouse of the genus Psocus, the top size of which is about 1 cm (0.4 in).
- Fleas (Siphonaptera). The largest species of flea is Hystrichopsylla schefferi. This parasite is known exclusively from the fur of the Mountain Beaver and can reach a length of 1.2 cm (0.5 in).
- Thrips (Thysanoptera). Members of the genus Phasmothrips are the largest kinds of thrips. The maximum size of these species is approximately 1.3 cm (0.5 in).