Black millipedes are slow-moving, segmented arthropods that feed primarily on decaying organic matter. They are detritivores, meaning they help recycle nutrients in the soil by consuming dead leaves and wood. These creatures are not able to bite or sting, nor are they venomous. However, when disturbed or handled roughly, black millipedes possess a potent chemical defense mechanism that can cause irritation upon contact.
The Millipede Defense: Clarifying Poison vs. Secretion
Millipedes are often incorrectly labeled as poisonous or venomous. Poisonous implies a creature is toxic if ingested, while venomous means it injects toxins via a bite or sting. The millipede’s defense is neither of these, as they lack the fangs or stingers required to inject venom. Instead, when they feel threatened, they typically coil into a tight spiral and release a fluid from microscopic pores, known as ozopores, along the sides of their body.
This defensive secretion is a mixture of various irritating chemicals that functions to deter predators. The chemical composition can include caustic substances like hydrochloric acid and organic acids. It also contains a group of compounds called quinones, such as benzoquinones and hydroquinones. Some species, particularly the flat-backed types, even produce hydrogen cyanide, which creates a noticeable odor of almonds.
The quinones are particularly effective as they are topical irritants and repellents that can chemically burn or stain skin. While the amount of chemical released is relatively small, it is sufficient to cause a significant reaction in sensitive individuals or small pets. This fluid is strictly a defense mechanism and is released only when the millipede is under stress.
Immediate Effects and Necessary First Aid
Contact with the defensive secretion can lead to noticeable symptoms on human skin. The most common reactions include localized burning, itching, and temporary skin irritation. A distinct and long-lasting effect of contact with quinone compounds is the severe staining of the skin, which can turn the area brown and sometimes persist for weeks or even months.
If the millipede fluid contacts the skin, the affected area should be washed immediately and thoroughly with soap and warm water. This action helps to remove the noxious chemicals and minimize irritation. Over-the-counter corticosteroid creams can be applied to treat any persistent rash or localized reaction.
Eye exposure presents a more serious situation, as the caustic nature of the chemicals can cause significant irritation. Symptoms may include pain, excessive tearing, conjunctivitis, and inflammation of the cornea. If the fluid enters the eyes, they must be flushed immediately and continuously with water for at least 20 minutes, followed by immediate professional medical attention. Ingestion by a small pet is generally not life-threatening due to the small quantity of fluid, but veterinary consultation is recommended if symptoms like vomiting or lethargy occur.
Distinguishing Millipedes from Other Garden Invertebrates
Millipedes are frequently mistaken for centipedes, but the two creatures have distinct physical differences. Black millipedes have a rounded, cylindrical body shape and move slowly. They are characterized by having two pairs of legs on almost every body segment.
Centipedes, by contrast, have a flatter body and move quickly. They possess only one pair of legs per body segment, and their legs typically project outward from the sides of their bodies. A centipede is a predator and is venomous, equipped with a pair of modified front legs called forcipules that can deliver a painful bite. Observing the body shape, speed of movement, and leg arrangement is the most reliable way to differentiate the harmless millipede from the biting centipede.