Millipedes are common invertebrates often encountered in gardens and sometimes indoors, leading many to wonder about their potential danger. Understanding the nature of millipedes, particularly the greenhouse millipede, helps to address common anxieties about their safety.
Understanding Greenhouse Millipedes
Greenhouse millipedes (Oxidus gracilis) are arthropods with elongated, segmented bodies. They typically measure 0.7 to 1 inch (18 to 24 mm) in length and have a dark brown or black coloration with pale legs. Each body segment features two pairs of legs, contributing to their slow, wave-like movement. They navigate using antennae, as they do not possess eyes.
These millipedes thrive in moist environments rich with decaying organic matter, such as leaf litter, mulch, and rotting wood. They are frequently found in garden beds, under rocks and logs, and can also inhabit greenhouses, basements, and garages, which is how they earned their common name. While native to Asia, greenhouse millipedes have been widely introduced globally, often transported via gardening soil.
A common concern is whether greenhouse millipedes are poisonous. Millipedes are not venomous and do not bite or sting humans. Their defense mechanism involves coiling their bodies into a tight spiral and secreting a fluid when threatened. This fluid contains chemicals like hydrogen cyanide and benzoquinones, which can be toxic if consumed by predators but are generally harmless to humans. Contact with these secretions may cause mild skin irritation, temporary discoloration, or, in sensitive individuals, an allergic reaction. If the fluid contacts the eyes, it can lead to irritation.
Interaction and Misconceptions
When encountering a greenhouse millipede, it is generally safe to handle them gently, perhaps with gloves, before relocating them to a suitable outdoor environment. These creatures are not aggressive and their primary defense is chemical secretion. Their presence in an ecosystem is beneficial, as millipedes are detritivores, meaning they feed on decaying plant material. This role helps to break down organic matter, recycle nutrients, and contribute to soil aeration and fertility.
A frequent misconception arises from confusing millipedes with centipedes, which are distinctly different arthropods. Centipedes possess a flattened body shape and have only one pair of legs per body segment, which extend outwards from their sides. They are fast-moving predators that hunt insects and other small creatures, delivering venom through a painful bite. While their venomous bites can be painful, they are typically not life-threatening to humans.
In contrast, millipedes have a rounded, cylindrical body with two pairs of legs per segment, positioned underneath. They move slowly and do not possess venomous fangs. Their defense involves coiling and releasing irritating chemicals. Understanding these differences clarifies that greenhouse millipedes pose no direct threat to humans.