Big Bugs and Colossal Crabs: 7 Invertebrates of Unusual Size

This segmented polychaete marine worm can attain lengths of 10 feet. It bristles with parapodia, protrusions from its body segments that function like legs, helping it to slither through the sediments in which in buries most of its body while lying in wait for prey. When it senses a passing sea creature with one of its five antennae-like palps, it launches itself from its burrow and snares it with a pair of wickedly sharp mandibles. Incongruously, given its hideous visage, the species shimmers with purple iridescence…Alien by way of Haus of Gaga.

Five species of goliath beetle lumber through the forests of Africa. They are probably the heftiest insects alive. Their blubbery white larvae may reach almost a quarter of a pound. Adults are a bit lighter; they can even fly. Part of the scarab beetle family, they are less scatalogically inclined than some of their relatives, preferring to feast on fruit and sap rather than feces. Their wings are ground up and used in fertility and hunting rituals by the Ndembu tribe.

Stop and rest your eyes on this lovely lepidopteran…there’s nothing else pretty on this list, I assure you. The gargantuan atlas moth boasts a wing span of up to a foot. It has the largest wingspan of any butterfly or moth. For one so large, surprisingly, it does not feed as an adult. It doesn’t even have a mouth.

As terrifying as they may look, giant isopods are benign creatures, usually found scuttling around in the depths and nibbling on dead things that have drifted down from above. They love a nice juicy whale corpse. A type of crustacean, they are enormous marine relatives of the familiar roly-polies, or pillbugs, known to most children who have spent any amount of time digging around in the dirt for their charming habit of curling into a ball when threatened. Giant isopods can do the same, though they can also swim away from potential threats with surprising grace.

Coconut crabs, so-named because of their supposed affinity for coconut flesh, are actually generalist scavengers. Native to islands in the Pacific and Indian oceans, they will eat fallen fruit (including coconuts), carrion, and even human garbage. The largest terrestrial arthropods in the world, they are actually huge hermit crabs, reaching up to 9 pounds. Only the very young wear shells, though. The abdomens of the adults are covered by a hard exoskeleton. They may live 60 years.

These monstrous relatives of crickets, found on off-shore islands of New Zealand, are, despite their terrifying appearances, vegetarian, though some of their smaller relatives are carnivorous. They are exemplars of a phenomenon known as island gigantism…the lack of competition for resources and paucity of predators afforded by isolated island life have allowed these insects to evolve into hulking, ponderous browsers. A pregnant specimen of the largest species, Deinocrida fallai, was recorded at 71 grams.

The Japanese spider crab is the largest living arthropod. When its legs are fully extended, it can straddle 13 feet. Most of that width is from its spindly gams; the body itself is only about a foot wide. The gigantic crustaceans inhabit depths of up to 1,000 feet in Japan’s Pacific waters. They slowly plod across the seafloor in search of detritus to eat. Unlike other spider crabs, which flamboyantly adorn themselves with bits of debris, the Japanese species prefers to go au naturel.