The Three Arthropods / Arachnids that Have the Most Legs
Arthropods are a group of animals including insects, crustaceans and myriapods. Arthropods have many legs with jointed feet and molt their exoskeleton several times throughout their lives. Arachnids are a separate group of insects including ticks, mites, harvestmen, and spiders; each has only two body sections.
Many animals have two legs, some have four but some have more. Most insects have six legs, three body segments, and an exoskeleton. However, there are a couple insects that have much more than six legs such as the centipede and the millipede. The name centipede and millipede suggests that they have one hundred and one thousand legs accordingly; however, millipedes are born with only three pairs of legs and most have less than one hundred legs. As the millipede grows more segments in its’ typical seven year life span, it also grows more legs; there are two legs per body segment. The record holding millipede for the largest amount of legs had seven hundred fifty legs, still two hundred fifty legs shy from the thousand legs most people expect of a millipede. Millipedes are an interesting arthropod in that they coil their body into a spiral to protect their belly when threatened; their exoskeleton segments then protect them.
Another arthropod with many legs is a crustacean: the crab. The crab is a decapod, meaning it has ten legs. Eight of these legs are used for mobility and two are used for capturing food and defense. Like insects, crabs have complex eyes, which allows them to see in multiple directions. Also like insects, crabs have a thick exoskeleton, which they shed periodically for a larger one. Their exoskeleton is made of chitin and calcium and protects them from predators and their environment. Crabs are opportunistic feeders and prey on mussels, fish, plant matter, and animal carcasses. Unfortunately, the crab population has declined in recent years due to pollution and an excess of nutrients in the water from plant and animal waste and fertilizer.
Arachnids have just two fewer legs than crabs but two more than most insects. Unlike insects, arachnids do not have antennae or mandibles. The arachnids called spiders have eight eyes and poor eyesight. In fact, they use hairs on their body to sense the vibrations around them. Spiders are carnivores and prey on insects by injecting them with venom as they spin them rapidly in their webs. Arachnids can only digest liquid food, so they inject their prey with digestive chemicals before sucking out the resulting juice.