Garden Millipede

Oxidus gracilis, commonly known as the greenhouse millipede or garden millipede, belongs to the family Paradoxosomatidae within the order Polydesmida. Adults typically measure 19-25 mm in length and are characterized by their flattened, shiny dark-brown to black bodies, possessing a series of paranota (lateral keels) giving them a somewhat keeled appearance, distinguishing them from truly cylindrical millipedes. They exhibit a life cycle lasting 1-2 years, with females depositing clutches of 20-30 eggs in soil, which hatch into larvae with fewer segments and legs, gradually adding more segments with each molt. Optimal environmental conditions for development include temperatures between 20-25°C and high relative humidity (>75%), with lower temperatures prolonging development. An identifying characteristic is the presence of repugnatorial glands that secrete hydrogen cyanide and benzaldehydes, causing a distinct almond-like odor when disturbed.

This species exhibits primarily nocturnal activity, emerging from protected harborages to forage under conditions of high humidity. While lacking complex social structures, large aggregations can occur during dispersal or when favorable conditions are found, though this is not indicative of true sociality. Their feeding behavior is strictly detritivorous, consuming decaying plant matter, leaf litter, and occasionally soft-bodied living plant tissues if other food sources are scarce, acting as important decomposers in their natural habitat. When threatened, O. gracilis employs a defensive coiling mechanism, protecting its vulnerable ventral side, and concurrently exudes its noxious chemical secretions, deterring predators. Although not directly harmful, mass indoor migrations can trigger allergic reactions in sensitive individuals due to these secretions, and their sheer numbers can be a significant nuisance.