Arthropods
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50 free Arthropods trivia questions with answers — trivia quiz, new questions added Oct 2026.
Arthropods are the most successful animals on Earth. Insects, spiders, crabs, shrimp and their many-legged relatives all share one basic design, a segmented body inside a suit of armor that has to be shed and replaced as the animal grows. Between them they account for most of the animal species ever named. This quiz covers phylum Arthropoda the way a biology class does. It asks how the major groups are told apart, from insects and arachnids to crustaceans and the leggiest land-dwellers, how an arthropod breathes, sees and pumps its blood, and which terms a zoology exam expects you to know. It also meets the giants, the oddballs and the fossils that make the group so much fun. It is written for high school and college students revising classification, and for anyone who likes bugs, crabs and creepy-crawlies. The opening questions are friendly and the later ones are tougher, and every answer comes with a short explanation.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Which sea creature's bright blue blood is harvested to test medicines for dangerous bacterial toxins?
Horseshoe crab
The horseshoe crab has blood containing a chemical that reveals bacterial toxins, which drug makers rely on. Despite the name, the animal is closer to spiders than to true crabs.
Q 02Which creature that rolls into a ball under garden logs is a crustacean rather than an insect?
Pill bug
The pill bug is a woodlouse, a land-living relative of crabs and shrimp. It loses water quickly, which is why it keeps to damp, dark places such as the underside of rocks.
Q 03Which blood-feeding parasite that spreads Lyme disease is an eight-legged arachnid, not an insect?
Tick
The tick belongs to the same class as spiders and mites, and an adult has eight legs. Fleas, lice and bedbugs are all six-legged insects.
Q 04The first animal ever found with more than a thousand legs lives deep underground in which country?
Australia
Australia produced the record-breaker from mining drill holes up to 60 meters deep: an eyeless, thread-like animal with as many as 1,306 legs. The previous record was 750.
Q 05Meganeura, an extinct insect with a 70-centimeter wingspan, resembled which living insects?
Dragonflies
Dragonflies are the closest living look-alikes of Meganeura, which hunted other insects about 300 million years ago. The biggest modern species is far smaller.
Q 06Bagheera kiplingi, a jumping spider that eats mostly plants, is named after a character from which classic?
The Jungle Book
The Jungle Book supplied the genus name, after Kipling's black panther Bagheera. The spider lives on acacia trees in Central America and eats protein-rich nubs that the trees produce.
Q 07The novelty aquarium pets sold to children as Sea-Monkeys are actually which tiny crustaceans?
Brine shrimp
Brine shrimp lay eggs that can lie dormant for years until they touch water, which is why a dry packet seems to spring to life. The kits were developed in the United States in 1957.
Q 08Spiders have no muscles for straightening their legs, so what do they use to extend them instead?
Hydraulic pressure
Hydraulic pressure extends a spider's legs: fluid is pumped in to push each joint straight. That is why the legs of a dead spider curl up.
Q 09Which crustaceans, long classed as mollusks, did Charles Darwin describe in a series of monographs?
Barnacles
Barnacles are stuck down by cement glands on the head, so each adult lives fixed upside down by its forehead. Darwin's son assumed that every father studied them at home.
Q 10Lobsters, crabs and tarantulas have bluish blood because its key pigment contains which metal in place of iron?
Copper
Copper gives the pigment hemocyanin its blue color, in the way iron gives human hemoglobin its red. Without its cargo, hemocyanin is colorless.
Q 11Which tough carbohydrate, also found in the cell walls of fungi, forms the exoskeleton of arthropods?
Chitin
Chitin is the second most abundant polysaccharide in nature, behind only the cellulose of plants. An estimated billion tons of it are made every year.
Q 12The word arthropod comes from two Greek words that together describe which feature of the animals?
Jointed leg
Jointed leg is the meaning, from 'arthron', a joint, and 'pous', a foot or leg. The term first appeared in anatomical descriptions published in 1832.
Q 13What is the scientific name for the shedding of an old exoskeleton that lets an arthropod grow?
Ecdysis
Ecdysis leaves the animal briefly helpless: the new exoskeleton is so soft and wrinkled at first that its owner cannot support itself and can hardly move.
Q 21Insects and springtails both belong to which arthropod subphylum, the largest of them all?
Hexapoda
Hexapoda, from the Greek for six legs, takes in the true insects plus three small groups of wingless animals that were once counted among them.
Q 22Which mouthparts, shaped as fangs or pincers, give spiders, mites and their relatives their subphylum name?
Chelicerae
Chelicerae in nearly all spiders are hollow fangs connected to venom glands, used to inject venom into prey or into anything that threatens them.
Q 23Which predators, with one pair of legs per body segment, inject venom through modified front legs?
Centipedes
Centipedes never have exactly 100 legs, despite the name: every species has an odd number of leg pairs, from 15 up to 191.
Q 14Which middle section of an adult insect's body carries all three pairs of legs and any wings?
Thorax
The thorax holds the flight muscles as well as the legs. Adult insects are the only arthropods that ever have wings, with up to two pairs.
Q 15Through which small openings along the sides of the body do most insects take in air?
Spiracles
Spiracles exchange gas less efficiently as a body gets bigger, which is one limit on how large an insect can grow.
Q 16What name is given to the blood-like fluid that circulates through an arthropod's body cavity?
Hemolymph
Hemolymph in insects mainly carries nutrients rather than the gas they breathe, which reaches the tissues through a separate system of air tubes.
Q 17Which breathing organs of spiders are built from stacks of alternating air pockets and thin tissue plates?
Book lungs
Book lungs get their name because the stacked layers look like the pages of a folded volume. They are a land version of the page-like gills of sea-dwelling relatives.
Q 18An arthropod's heart pumps blood into body spaces rather than sealed vessels, an arrangement called what?
Open circulation
Open circulation means the organs are bathed directly in blood inside one long body cavity. The heart is a muscular tube running just under the animal's back.
Q 19Arthropods share with humans, but not with adult starfish, which type of body symmetry?
Bilateral
Bilateral symmetry means a body with a head end, a tail end and matching left and right sides. Starfish begin that way as embryos, then switch to a five-part layout.
Q 20In insects with complete metamorphosis, which stage comes between the larva and the winged adult?
Pupa
The pupa is the third of four life stages, after egg and larva. A butterfly's is known as a chrysalis.
Q 24Arthropleura, the largest land arthropod of all time, was a two-meter ancient form of which animals?
Millipedes
Millipedes of this giant kind left fossil trackways up to 50 centimeters wide. Arthropleura reached at least 2 meters in length, and possibly more than 2.5.
Q 25Which extinct marine arthropods, common as fossils, died out in the mass extinction that ended the Permian?
Trilobites
Trilobites lived in the oceans for almost 270 million years, and more than 22,000 species have been described. Only a handful were left when the end came.
Q 26Which long-legged arachnids, often mistaken for spiders, have no venom, no silk and a body like a single oval?
Harvestmen
Harvestmen are the subject of an urban legend that calls them the most venomous animals alive. In fact none of the 6,650-plus known species has venom glands at all.
Q 27Genetic studies show that termites, once given their own order, are a social branch of which insects?
Cockroaches
Cockroaches turn out to include termites deep inside their family tree, with wood-eating roaches as the nearest kin. Termites are not ants, despite the old nickname white ants.
Q 28Which insects, with about 400,000 described species, make up roughly a quarter of all known animals?
Beetles
Beetles are set apart by front wings hardened into protective cases. Estimates of the true number of species run from 0.9 million to 2.1 million.
Q 29Which soft-bodied close relatives of arthropods snare their prey by squirting sticky slime?
Velvet worms
Velvet worms, named for their velvety texture, squirt a milky glue from glands beside the mouth. About 232 species have been described, though many more probably exist.
Q 30Which branch of zoology, sometimes confused with the study of word origins, is devoted to insects?
Entomology
Entomology once covered spiders, crustaceans and other arthropods as well, because the word insect used to be applied far more loosely.