Millipedes are common invertebrates found in diverse habitats, from gardens to forests. Understanding a millipede’s appearance is helpful for accurate identification and appreciating these fascinating arthropods. This article details the specific features that define a millipede, helping to distinguish it from similar organisms.
Key Physical Features
A millipede’s body is typically elongated and segmented, resembling a worm. Most species exhibit a cylindrical or slightly flattened body shape, providing a robust, tube-like structure. Their coloration commonly ranges from golden-brown to dark brown or black, though some species display vibrant patterns or markings. The overall length can vary significantly, from tiny species measuring a few millimeters to larger ones reaching up to 35 centimeters (14 inches).
The defining characteristic of a millipede is the arrangement of its legs. Each body segment, except for the first few behind the head and the very last ones, possesses two pairs of jointed legs. These double-legged segments, known as diplosegments, form from the fusion of two embryonic segments. The head is small and rounded, featuring a single pair of short, elbowed antennae used for sensing its surroundings, as millipedes have poor vision and simple eyes primarily detecting light and dark. Their numerous legs move in a distinctive slow, wave-like motion, creating a ripple effect as the animal progresses steadily along surfaces.
Millipedes Versus Centipedes
Millipedes are often confused with centipedes due to their segmented bodies and many legs, but distinct physical differences allow for clear identification. The most apparent distinction lies in their leg arrangement: millipedes have two pairs of legs per body segment, while centipedes possess only one pair per segment. Millipedes typically have a more rounded or cylindrical body, whereas centipedes tend to have flatter, more flexible bodies.
Another distinguishing feature is the position of their legs relative to their bodies. Millipedes’ legs are positioned underneath their body, often appearing less prominent from above, contributing to their burrowing capabilities. In contrast, centipedes have longer legs that extend out to the sides of their bodies.
Millipedes generally move slowly, employing their many legs in a coordinated wave. Centipedes, being predatory, are known for their much faster and more agile movements, darting quickly across surfaces. Their antennae also differ; millipedes have short, bent antennae, while centipedes possess longer, thread-like antennae.
Diversity in Appearance
While the general body plan of millipedes is consistent, there is considerable diversity in appearance across the approximately 12,000 described species. Beyond the common black and brown hues, some millipede species exhibit striking colors such as yellow, orange, or blue, and some may have banded patterns. These brighter colorations often serve as a warning to predators, indicating the presence of chemical defenses.
Variations also occur in body textures and shapes, with some groups displaying unique features like keel-like extensions along their body segments. This spectrum of appearances, from smooth-bodied burrowers to species with rougher textures or specialized body modifications, showcases the adaptability of millipedes to different environments.