Many things in nature have six legs – insects, arachnids, crustaceans – but not all of them can walk. So what could the answer be to the riddle “What has six legs but can’t walk?” Let’s explore some possibilities.
Insects
Insects make up the largest and most diverse group of organisms with six legs. All insects have six jointed legs, three body parts, a hard exoskeleton, and go through metamorphosis. With their six strong legs, most insects are excellent walkers. Grasshoppers can leap 20 times their body length. Cockroaches can sprint nearly 50 body lengths per second. Water striders can literally walk on water. But not all insects with six legs can walk.
Larval Insects
Many larval insects have six legs but cannot walk. Take caterpillars, the larval form of butterflies and moths. Caterpillars have six true legs on their thorax, but these are relatively small and weak compared to their large, fleshy bodies. Instead of walking, caterpillars crawl by gripping with soft, stubby prolegs on their abdomen and inching their bodies forward. So caterpillars technically have six legs but cannot truly walk.
Mayflies
Mayfly nymphs, the juvenile aquatic form of mayflies, also have six legs as larvae but cannot walk. They have gills along their abdomen and three long caudal filaments. With their soft bodies and weak legs, mayfly nymphs are built for swimming, not walking. They would not survive for long out of water. So mayfly nymphs, though equipped with six legs, cannot walk.
Caddisfly Larvae
Caddisfly larvae have six legs, but they do not use them for walking. Caddisfly larvae build cases out of debris such as grains of sand or pieces of leaves. They live inside these protective tubular cases, dragging them along as they crawl using tiny hook-like appendages on their abdomen. Their long spindly legs are not strong enough to walk, so caddisfly larvae with six legs cannot truly walk either.
Aquatic Insects
Many other aquatic larval insects have six legs but cannot walk. Dragonfly nymphs, stonefly nymphs, alderfly larvae, dobsonfly larvae – they all have six legs as immature insects, but their legs are designed for grasping prey or clinging to rocks in water, not walking. Without the buoyancy of water, these leggy larvae would be helpless on land.
Crustaceans
Let’s move beyond insects to another group of six-legged arthropods – crustaceans. Crustaceans include crabs, lobsters, crayfish, shrimp, barnacles, and many others. Many crustaceans start life with six legs, so could the answer be a young crustacean?
Copepods
Copepods are a group of tiny aquatic crustaceans abundant in fresh and salt water. The larvae have a segmented body and six pairs of legs for swimming. But copepods are so small, less than 1 mm in size, that their little legs cannot support them for walking. When removed from the water, these tiny crustaceans with six legs will convulse but cannot walk.
Barnacle Larvae
Barnacle larvae go through two main stages. After hatching, they are free-swimming nauplii with antennae for propelling themselves. Later, they develop into cyprid larvae that use their six thoracic legs – five for swimming and one for anchoring themselves to surfaces. While cyprid larvae have six legs, they cannot use them for walking, only for latching onto rocks or other substrates. Their legs are specialized for anchoring, not walking.
Isopods
Isopods like pill bugs and sow bugs are crustaceans with seven pairs of legs. But baby isopods hatch with only six pairs of legs. Their first molt adds the seventh pair. So newly hatched isopods have six legs but cannot really walk – they can only crawl clumsily like tiny slaters. Their small size and immature leg development means these newborn isopods cannot walk.
Mysid Shrimp
Mysid shrimp larvae hatch with six legs, but these tiny limbs are used primarily for swimming and clinging to jellyfish, their hosts. The legs of mysid larvae are not robust enough to support walking. Only after further development and molting do they gain the ability to walk properly. Therefore, tiny newborn mysid shrimp with six legs cannot walk.
Arachnids
Beyond insects and crustaceans, some arachnids also hatch with six legs. Arachnids include spiders, scorpions, mites, and ticks. Could an arachnid be the answer to our riddle?
Spiderlings
When spider eggs hatch, out emerge spiderlings with six legs. However, these tiny spider babies cannot yet walk properly. They cling to their mother’s back and ride around until after their first molt. Once they molt and grow stronger legs, spiderlings detach and start walking independently. But upon initial hatching with six legs, they lack the leg strength and coordination required to walk.
Larval Ticks
Ticks go through three stages in their development: larva, nymph, and adult. Larval ticks hatch from eggs with six legs. But these legs are not designed for walking. Instead, newly hatched tick larvae use their legs to climb up vegetation and wait for a host animal to latch onto for their first blood meal. Since their legs are specialized for clinging and cannot support walking, six-legged larval ticks cannot walk.
Scabies Mites
Sarcoptes scabiei, the mite that causes scabies in humans, hatches from eggs with six legs. These microscopic mites use their legs to burrow into the skin and crawl across the surface of the skin. However, their legs are far too small and weak to enable walking in the traditional sense. Instead, newborn scabies mites can only crawl very slowly using their six tiny legs.
Conclusion
As we have seen, many small invertebrates start life with six legs – insect larvae, crustacean larvae, baby arachnids. But while equipped with six legs, these tiny creatures cannot yet walk properly. Reasons include:
– Legs are too small, weak, undeveloped
– Legs adapted for other uses like swimming, clinging, anchoring
– Body is too soft, small, or tail-heavy
– Lack strength and coordination required for walking
So the answer to the riddle “What has six legs but can’t walk?” appears to be: baby insects, crustaceans, and arachnids! Their six legs are not used for walking, at least not at first. Only later in development will some of these creatures gain the ability to walk on their six legs.
Creatures With Six Legs That Don’t Walk – Examples
| Creature | Reasons It Cannot Walk on Six Legs |
|---|---|
| Caterpillars | Soft body, weak legs meant for crawling |
| Mayfly nymphs | Weak legs meant for swimming |
| Caddisfly larvae | Fragile legs, crawl using abdomen |
| Copepods | Tiny size, legs for swimming |
| Barnacle larvae | Legs for anchoring and swimming |
| Newly hatched isopods | Immature leg development |
| Mysid shrimp larvae | Legs for clinging, swimming |
| Spiderlings | Ride on mother’s back, undeveloped legs |
| Larval ticks | Legs for clinging, not walking |
| Scabies mites | Microscopic legs for crawling |
Summary
In summary, while many tiny newborn creatures technically have six legs, these legs are often too small or weak for walking. Only later in life will some of these creatures gain the strength and coordination to walk on their six legs. So the best answer to the riddle is tiny larval and juvenile forms of insects, crustaceans, and arachnids!
