Science, Tech, Math › Animals & Nature Invertebrate Photo Gallery Share Flipboard Email Print Science, Tech, Math Amphibians Birds Habitat Profiles Mammals Reptiles Insects Marine Life Forestry Dinosaurs Evolution View More By Laura Klappenbach Ecology Expert M.S., Applied Ecology, Indiana University Bloomington B.S., Biology and Chemistry, University of Illinois at Urbana-Champaign Laura Klappenbach, M.S., is a science writer specializing in ecology, biology, and wildlife. our editorial process Laura Klappenbach Updated August 11, 2018 Invertebrates are animal groups that lack a vertebra, or backbone. Most invertebrates fall into one of six categories: sponges, jellyfish (this category also includes hydras, sea anemones, and corals), comb jellies, flatworms, mollusks, arthropods, segmented worms, and Echinoderms. Pictured below are invertebrates including horseshoe crabs, jellyfish, ladybugs, snails, spiders, octopus, chambered nautiluses, mantises, and more. 01 of 12 Crab Sandeep J. Patil / Shutterstock Crabs (Brachyura) are a group of crustaceans that have ten legs, a short tail, a single pair of claws, and a thick calcium carbonate exoskeleton. Crabs live in a wide variety of places—they can be found in every ocean around the world and also inhabit freshwater and terrestrial habitats. Crabs belong to the Decapoda, an arthropod order that consists of numerous ten-legged creatures that include (in addition to crabs) crayfish, lobsters, prawns, and shrimp. The earliest known crabs in the fossil record date from the Jurassic Period. Some primitive predecessors to modern crabs are also known from the Carboniferous Period (Imocaris, for example). 02 of 12 Butterfly Christopher Tan Teck Hean / Shutterstock Butterflies (Rhopalocera) are a group of insects that include more than 15,000 species. Members of this group include swallowtail butterflies, birdwing butterflies, white butterflies, yellow butterflies, blue butterflies, copper butterflies, metalmark butterflies, brush-footed butterflies, and skippers. Butterflies are notable among insects as being superb migrators. Some species migrate long distances. The most famous of these is perhaps the Monarch butterfly, a species that migrates between its winter grounds in Mexico to its breeding grounds in Canada and the northern parts of the United States. Butterflies are also known for their life cycle, which consists of four stages, egg, larva, pupa and adult. 03 of 12 Jellyfish Sergey Popov V / Shutterstock Jellyfish (Scyphozoa) are a group of cnidarians that includes more than 200 living species. Jellyfish are primarily marine animals, although there are a few species that inhabit freshwater environments. Jellyfish occur in inshore waters near coastlines and can also be found in the open ocean. Jellyfish are carnivores that feed on prey such as plankton, crustaceans, other jellyfish, and small fish. They have a complex life cycle—throughout the course of their life, jellyfish take on a number of different body forms. The most familiar form is known as the medusa. Other forms include the planula, polyp, and ephyra forms. 04 of 12 Mantis Frank B. Yuwono / Shutterstock Mantises (Mantodea) are a group of insects that includes more than 2,400 species. Manids are best known for their two long, raptorial forelegs, which they hold in a folded or "prayer-like" posture. They use these limbs to capture their prey. Mantises are formidable predators, considering their size. Their cryptic coloration enables them to disappear into their surroundings as they stalk their prey. When they get within striking distance, they snatch their prey with a quick swipe of their forelimbs. Mantises feed primarily on other insects and spiders but also sometimes take larger prey such as small reptiles and amphibians. 05 of 12 Stove-Pipe Sponge Nature UIG / Getty Images Stove-pipe sponges (Aplysina archeri) are a species of tube sponge that has a long tube-like body that resembles, as its name indicates, a stove pipe. Stove-pipe sponges can grow to lengths of up to five feet. They are most common in the Atlantic Ocean and are especially prevalent in the waters that surround the Caribbean Islands, Bonaire, the Bahamas, and Florida. Stove-pipe sponges, like all sponges, filter their food from the water. They consume tiny particles and organisms such as plankton and detritus that are suspended in the water current. Stove-pipe sponges are slow-growing animals that can live for hundreds of years. Their natural predators are snails. 06 of 12 Ladybug Westend61 / Getty Images Ladybugs (Coccinellidae) are a group of insects that have an oval body that is (in most species) bright yellow, red, or orange color. Many ladybugs have black spots, although the number of spots varies from species to species (and some ladybugs lack spots altogether). There are about 5000 living species of ladybugs that have been described by scientists so far. Ladybugs are celebrated by gardeners for their predatory habits—they eat aphids and other destructive pest insects. Ladybugs are known by several other common names—in Great Britain, they are known as ladybirds and in some parts of North America, they are called ladycows. Entomologists, in an attempt to be more taxonomically correct, prefer the common name ladybird beetles (since this name reflects the fact that ladybugs are a type of beetle). 07 of 12 Chambered Nautilus Michael Aw / Getty Images The chambered nautilus (Nautilus pompilius) is one of six living species of nautiluses, a group of cephalopods. Chambered nautiluses are an ancient species that first appeared about 550 million years ago. They are often referred to as living fossils since living nautiluses so closely resemble those ancient ancestors. The shell of a chambered nautilus is its most distinguishing characteristic. The nautilus shell consists of a series of spirally arranged chambers. As the nautilus grows new chambers are added such that the newest chamber is located at the shell opening. It is in this newest chamber that the body of the chambered nautilus resides. 08 of 12 Grove Snail Santiago Urquijo / Getty Images Grove snails (Cepaea nemoralis) are a species of land snail that is common throughout Europe. Grove snails also inhabit North America, where they were introduced by humans. Grove snails vary greatly in their appearance. A typical grove snail has a shell of pale yellow or white with multiple (as many as six) dark bands that follow the spiral of the shell. The background color of the grove snail's shell can also be reddish or brownish in color and some grove snails lack dark bands altogether. The lip of the grove snail's shell (near the opening) is brown, a characteristic that earns them their other common name, the brown-lipped snail. Grove snails live in a wide variety of habitats including woodlands, gardens, highlands and coastal regions. 09 of 12 Horseshoe Crab Shane Kato / iStockphoto Horseshoe crabs (Limulidae) are, despite their common name, not crabs. In fact, they are not crustaceans at all but are instead members of a group known as the Chelicerata and their closest cousins include arachnids and sea spiders. Horseshoe crabs are the only living members of a once widely-successful group of animals that peaked in diversity some 300 million years ago. Horseshoe crabs live in the shallow coastal waters that surround North America and Southeast Asia. They are named for their tough, horseshoe-shaped shell and long spiny tail. Horseshoe crabs are scavengers that feed on mollusks, worms and other small marine animals that live in seafloor sediments. 10 of 12 Octopus Jens Kuhfs / Getty Images Octopuses (Octopoda) are a group of cephalopods that include about 300 living species. Octopuses are highly intelligent animals and exhibit good memory and problem-solving skills. Octopuses have a complex nervous system and a brain. Octopuses are soft-bodied creatures that have no internal or external skeleton (although a few species have vestigial internal shells). Octopuses are unique in that they have three hearts, two of which pump blood through the gills and the third of which pumps blood throughout the rest of the body. Octopuses have eight arms that are covered on the under-side with suction cups. Octopuses live in many different marine habitats including coral reefs, the open ocean, and the sea floor. 11 of 12 Sea Anemone Jeff Rotman / Getty Images Sea anemones (Actiniaria) are a group of marine invertebrates that anchor themselves to rocks and the sea floor and capture food from the water using stinging tentacles. Sea anemones have a tubular-shaped body, a mouth encircled by tentacles, a simple nervous system, and a gastrovascular cavity. Sea anemones disable their prey using stinging cells in their tentacles called nematocysts. The nematocysts contain toxins that paralyze the prey. Sea anemones are cnidarians, a group of marine invertebrates that also includes jellyfish, corals, and hydra. 12 of 12 Jumping Spider James Benet / iStockphoto Jumping spiders (Salticidae) are a group of spiders that includes about 5,000 species. Jumping spiders are notable for their superb eyesight. They have four pairs of eyes, three of which are fixed in a specific direction and a fourth pair that they can move to focus on anything that catches their interest (most often prey). Having so many eyes gives jumping spiders great advantage as predators. They have virtually 360° vision. If that weren't enough, jumping spiders (as their name implies) are powerful jumpers as well, a skill that enables them to pounce on their prey.