How Many Legs Do Centipedes Have? Millipedes? Other Insects?

While a majority of people believe all centipedes have 100 legs, that cannot be further from the truth. In fact, the number of legs on a given centipede largely depends on its species. It is difficult to define each type of centipede, as there are thought to be approximately 8,000 species worldwide. Out of that 8,000, only some 3,000 have been described.

Centipedes belong to the Chilopoda class, which means they have one pair of jointed legs per body segment. The number of body segments a centipede possesses is, again, contingent on the species. Centipedes that fall under the orders Lithobiomorpha and Scutigeromorpha, for instance, have 15 pairs of legs. Geophilomorphs, on the other hand, can have up to 177 pairs of legs. Meanwhile, members of the Scolopendromorpha order can consist of 21 to 23 pairs of legs.

Interestingly, not all centipedes are born with their entire collection of legs. Only the orders Geophilomorpha and Scolopendromorpha display epimorphic behavior, with all pairs of legs appearing during the embryonic stages. Conversely, centipedes that belong to the orders Lithobiomorpha, Scutigeromorpha, and Craterostigmomorpha grow their legs over time, which makes them anamorphic.

Although the name imparts the idea that centipedes have 100 legs, most species of the multi-legged pests do not even come close. Similarly, millipedes do not have 1,000 legs, despite being named as such. Additional insects with many legs include spiders and ticks, among others.

Importance of a Centipede’s Legs

Centipedes are invertebrate predators. They use their legs located on the body segment behind their heads as hunting fangs. There are also sensory bristles on the last pair of the centipede’s legs. These bristles function as an auxiliary pair of antennae, giving centipedes the ability to travel backward when trapped in confined spaces. Their jointed legs are also longer the farther away they are from the centipede’s head. This helps them with balance and agility.

Another fascinating fact about the centipede’s legs is that they can be discarded when the situation calls for it. Centipedes are able to remove their legs when their life is threatened. However, those legs are not lost forever. The creepy crawlers can actually regenerate them afterward.

Do Centipedes Bite?

While not all centipedes pose a threat to humans, some species do. Centipedes have hollow legs that resemble pincers and are used to pierce the skin. Because their mouthparts are not used in the process, these are not technically “bites.” Regardless, when a centipede does pierce human skin, they release venom into the wound.

Centipede “bites” are not fatal to adults, though they can be very painful. Symptoms include swelling, redness, pain, skin necrosis, local bleeding, headache, fever, weakness, palpitations, itching, and, rarely, nausea, and vomiting. However, these bites are more dangerous to small children and those who have bee allergies, with larger centipedes capable of causing anaphylactic shock.

If a centipede does bite you, it is important to rinse the bite side with cold water and disinfect the wound immediately. Put some ice over it to limit the spread of the venom. The degree of envenomation and the species of the centipede will largely dictate the type of treatment you require. You may be instructed to undergo a urine test or an EKG. Painkillers and other medication may be prescribed. In any case, it is best to consult a medical professional.

How Many Legs Do Millipedes Have?

Much like centipedes, the same form of misunderstanding is present when talking about millipedes. Contrary to popular belief, millipedes do not possess 1,000 legs. No known species has been documented to have 1,000 legs. An estimated 12,000 species of millipedes exist in the world today, although the record for the most number of legs belongs to the Illacme plenipes with 750.

While many people continue to interchange centipedes and millipedes, the two invertebrates have several differing characteristics. Centipedes are flatter in appearance and have one pair of jointed legs per body segment. Millipedes, on the other hand, are rounder and have two pairs of jointed legs on most body segments (which means they belong to the Diplopoda class). Centipedes also move quicker than their multi-legged cousins.

Additionally, centipedes have legs attached to the side of their bodies, whereas millipedes have legs attached to the underside of their bodies. Centipedes are predominantly carnivores, while millipedes are detritivores, which means they feed on organic waste. However, some known species of millipedes are herbivores, and a select few are carnivores. The antennae found on centipedes are long and come to a point. In comparison, millipedes have short antennae that have more rounded ends.

Do Millipedes Bite?

Millipedes do not bite nor do they sting, so they are not hazardous to humans. Their diet consists of dead plants and fungi, with only a few species being predatory in nature. While humans can rest easy knowing millipedes do not bite, they can be a nuisance to homeowners and gardeners.

Unlike centipedes, which run or bite when threatened, millipedes curl into a tight coil when they feel predators looming. Millipedes are not fast at all, so their defense mechanism mainly involves protecting their legs and softer underside using their tergites (hardened plates that act as armor found on their back).

Nonetheless, numerous species do secrete chemicals to keep themselves from harm, so they are not entirely defenseless. The foul-smelling compound is emitted through microscopic holes called ozopores also known as stink glands. Some of the chemicals they release can be corrosive and have been known to burn the exoskeletons of other small insects. Larger predators, on the other hand, may suffer burns on their skin and eyes. If you find yourself in contact with a millipede, it is best to give the area a thorough wash for good measure.

Millipedes that belong to the order Polyxenida are unluckier than others as they do not possess tergites or stink glands. Instead, they are covered in bristles. In one species, the Polyxenus fasciculatus, the bristles can disconnect from the body and ensnare ants.

Other Insects with Many Legs

While centipedes and millipedes often dominate the conversation, there are other many-legged critters worthy of being discussed. The two invertebrates, interestingly, do not even fall under the term “insect” as insects are defined as arthropods with six jointed legs. Nevertheless, many people have coupled them under the same classification. Technicalities aside, here are a few other insects known to have several legs.

Woodlouse

The woodlouse is an example of an insect (again, the term is used loosely here) that has several legs. Also known as a sowbug or pill bug, this creepy crawler has 14 legs. Technically speaking, the woodlouse is a crustacean belonging to the Isopoda order. Approximately 5,000 to 7,000 species are thought to exist worldwide.

Some homeowners regard woodlice as pests, although the benefits of having them in your garden often outweigh the negatives. They do like to feed on plants, but they also overturn soil and produce compost. Considering they do not spread disease nor bite, woodlice do not pose a threat to humans. In addition, they do not cause damage to structures.

Pauropods

Pauropods are arthropods that belong to the class Pauropoda. They resemble centipedes, but they are regarded as close relatives to millipedes. Pauropods have 9-11 pairs of legs, and they do not possess eyes or hearts. These critters are cylindrical and soft, often found living in the soil because they don’t like the light. Their diet mainly consists of mold and fungi.

Symphylans

Photo: Soniamartinez / CC BY-SA

Another relative of the centipede, Symphylans are arthropods of the class Symphyla. They are comparable in appearance to centipedes and are fast-moving like them, but the similarities usually stop there. Symphylans are much smaller in size and, unlike centipedes, lack venom. As their diet primarily consists of vegetation, they can cause agricultural damage by eating roots and seeds in the soil where they like to live.

Spiders

Scientifically, spiders do not fall under the umbrella of insects. Instead, they belong to the class Arachnida. There are currently at least 48,200 species of spiders around the world. These household pests have eight legs and strike fear in most humans. And while spider bites are notorious, only a handful of species release dangerous venom. Widow spiders and recluse spiders are thought to be some of the most perilous, but they are believed to only bite when cornered. In most cases, spiders flee at the hint of threat.

Ticks

Ticks are parasitic arachnids that consist of eight legs. They attach themselves to other living creatures and feed on their blood. While ticks can be found around the world, they are far more common in areas with warm and humid climates. Apart from blood-sucking, ticks can also be a health hazard to humans and animals because of their ability to transmit infections and diseases. Some species, like the Australian paralysis tick, are venomous and can induce tick paralysis.

Now that you know the main differences between centipedes and millipedes, it will be easier to identify them on the chance of an encounter. While their differing legs serve as the chief distinction, there are several other features that separate the two arthropods from one another. The next time you see an insect with countless legs, remember these points. They will come in handy.