Millipedes (Class Diplopoda) are long-bodied arthropods often confused with their predatory relatives, the centipedes. These slow-moving creatures are primarily detritivores, consuming decaying plant matter and recycling nutrients back into the soil. A common concern is whether these organisms pose a threat, specifically if they are capable of biting a person or a pet. This article clarifies the misconception surrounding millipede defense, explaining why biting is not a danger and detailing the chemical defense mechanisms they employ.
Are Millipedes Capable of Biting?
Millipedes are physically incapable of biting defensively or offensively, unlike centipedes which possess venomous fangs called forcipules. Their mouthparts are not designed to pierce or grab skin, even when the millipede feels threatened. Instead, millipedes possess a simple feeding apparatus known as the gnathochilarium, formed from fused maxillae.
This specialized structure functions solely for processing soft, decaying organic materials like rotten wood and leaves. The mechanism involves a soft grinding and scraping motion to ingest their diet. The delicate nature and simple design of the millipede’s mandibles mean they cannot penetrate human or animal skin.
The Mechanism of Chemical Defense
Since biting is not an option, the millipede’s primary method of protection relies on a passive, chemical defense strategy. When disturbed, their first response is typically to curl into a tight spiral or ball. This defensive posture effectively shields their vulnerable legs and soft underside within their hard, cylindrical exoskeleton.
If coiling does not deter a predator, the millipede deploys a defensive liquid secretion. This fluid is released from specialized glands called ozadenes, which open through microscopic pores known as ozopores. These ozopores are located along the sides of most body segments, allowing the millipede to coat itself in the repellent substance.
The release of this chemical is often a slow, oozing process. Some larger tropical species are capable of spraying the secretion a short distance, which contrasts with the quick venom injection used by centipedes. The sticky, foul-smelling liquid serves as a clear warning to potential predators.
Identifying the Toxic Compounds and Their Effects
The chemical composition of millipede defensive secretions is diverse, varying significantly between species, but generally involves a mix of irritating and toxic compounds. One common group of chemicals found are quinones, particularly benzoquinones. These are responsible for the millipede’s most noticeable effect on humans: skin staining. Quinones can cause a temporary brownish discoloration on the skin, along with a burning sensation or mild irritation that may last for hours or even days.
Some millipede species, particularly those in the order Polydesmida, produce trace amounts of hydrogen cyanide (HCN) as part of their defensive cocktail. HCN is a potent chemical that acts as a feeding deterrent and can be lethal to smaller organisms in a confined space. While the amount of HCN released by an individual millipede is insufficient to cause serious harm to a human, it can be detected by a distinct odor, often described as smelling like almonds.
The most significant danger from millipede secretions is to small pets, such as cats or dogs, if they ingest a millipede. The concentrated dose of defensive compounds, including quinones and HCN, can lead to serious illness requiring veterinary attention. Accidental contact with the eyes is the most severe human exposure risk, as the caustic chemicals can cause intense burning, inflammation, and temporary vision disturbances.
First Aid and Safe Handling Practices
Exposure to millipede secretions, while rarely a medical emergency, requires immediate and simple first aid to prevent irritation and staining. If the defensive fluid contacts the skin, the affected area should be washed thoroughly with soap and water. Washing should continue for up to twenty minutes to ensure the chemical residue is fully removed.
Avoid rubbing the area, especially before washing, and do not use alcohol to clean the site, as this may spread the chemical. If secretion enters the eyes, they must be flushed immediately with water for at least twenty minutes. Medical attention should be sought right away due to the risk of corneal inflammation.
When handling a millipede for relocation, wearing gloves is advisable to prevent direct contact with the secretions. If the millipede is indoors, sweeping it into a container and releasing it outside is the safest approach. If there is suspicion that a pet has ingested a millipede, immediate consultation with a veterinarian is recommended due to the higher toxicity risk posed by internal exposure.