Millipedes are multi-legged arthropods often encountered by homeowners and gardeners. These slow-moving creatures thrive in dark, damp environments, such as under logs, in leaf litter, or inside moist basements. Their presence often raises questions about their potential danger. Understanding their defense mechanisms is necessary to determine the threat they pose to humans and pets.
Clarifying the Difference: Poisonous Versus Venomous
Determining the danger posed by any creature requires specific biological terminology. From a scientific perspective, millipedes are neither venomous nor truly poisonous. A venomous animal, such as a snake or a spider, actively injects a toxin into a victim through a bite or a sting. Millipedes lack the fangs or stingers required to inject toxins, meaning they are not venomous.
A poisonous organism contains toxins that are harmful if ingested, inhaled, or absorbed through passive contact. Millipedes release a toxic substance as a defense, but they are not poisonous merely by being touched. While millipedes produce compounds that can be toxic, they are technically neither venomous nor poisonous in the conventional sense.
Defensive Secretions and Chemical Composition
The primary defense mechanism employed by millipedes is the passive release of noxious fluids. When disturbed, millipedes exude a substance from microscopic glands, known as ozadenes, which line the sides of their bodies. This fluid is known as a repugnatorial secretion, designed to deter predators like birds, rodents, and insects.
The chemical composition of these fluids varies significantly across species, but they often contain powerful compounds. A common component is a class of organic compounds called quinones, which are responsible for the fluid’s irritant effect. Some species, particularly tropical varieties, can produce trace amounts of hydrogen cyanide derivatives or alkaloids. These potent chemicals make the millipede unpalatable or mildly toxic to an attacker.
Practical Safety: Contact Symptoms and Treatment
If the defensive fluid contacts human skin, the reaction is typically localized and mild. Common symptoms include temporary skin irritation, a burning sensation, and redness at the point of contact. The quinone compounds can also cause noticeable skin discoloration, often appearing as a brown or black stain that can persist for several days or weeks.
If contact occurs, the affected area should be washed immediately and thoroughly with soap and water. Avoid rubbing the area before washing, as this can spread the irritant. If the fluid enters the eyes, it can cause severe symptoms like pain, inflammation, and potential damage to the cornea. This requires immediate rinsing for at least 20 minutes and prompt medical attention. Secretions pose a low risk to household pets, but they can cause oral irritation or digestive upset if ingested.
Millipedes Versus Centipedes: A Crucial Distinction
The confusion surrounding millipede danger often stems from their misidentification as centipedes, which are a different class of arthropods. Centipedes are predators equipped with venom and can deliver a painful bite to humans. The physical differences between the two provide a clear way to determine the level of threat.
Millipedes have a rounded, cylindrical body shape and move slowly, with two pairs of short legs attached to nearly every body segment. Centipedes possess a flattened body profile, are faster, and have only one pair of longer legs per body segment. Crucially, the centipede’s first pair of legs is modified into fangs, called forcipules, which are used to inject venom.