Some spiders do prey on millipedes, but this interaction is a rare and challenging hunt. Millipedes are slow-moving detritivores, but they are heavily armored and possess potent chemical defenses. This makes them a difficult and often dangerous meal for most generalist predators. Spiders that successfully hunt millipedes have evolved specific behavioral or morphological adaptations to overcome these specialized defenses.
The Fact of Millipede Predation
For most spiders, a millipede is not a preferred meal due to the significant risk involved. The millipede’s primary physical defense is its heavily mineralized, ring-like exoskeleton, which is difficult for a spider’s fangs to penetrate. Furthermore, when threatened, a millipede curls into a tight coil, shielding its softer underside and legs, effectively presenting a defensive shell to any attacker.
This high level of protection means that generalist spiders often attempt to attack millipedes but frequently fail or are severely harmed. The millipede’s physical structure and defensive posture force a spider to target specific, vulnerable areas, requiring a precise and risky maneuver. For most spiders, the energetic cost and danger associated with this prey limit millipede predation to adapted specialists.
Spider Families That Specialize in Millipedes
The most successful spider predators of millipedes are not necessarily those with the most potent venom, but those with unique adaptations for handling the prey’s tough exterior and defensive posture. Cellar spiders, belonging to the family Pholcidae, have been observed successfully subduing millipedes significantly larger than themselves. These long-legged spiders use an advanced behavioral strategy, leveraging their silk to incapacitate the prey without direct, sustained contact.
Other specialized predators include mygalomorphs, or “primitive” spiders like trapdoor spiders, which have downward-pointing, reinforced fangs. These spiders possess the robust chelicerae required to pierce the millipede’s armor. The ability to efficiently subdue heavily-armored prey often points to a dedicated evolutionary path, sometimes involving a change in hunting strategy from a venom-first approach to a mechanical-first attack.
Neutralizing Millipede Defensive Secretions
The millipede’s most formidable defense is its chemical arsenal, released from specialized glands, called ozadenes, along its body segments. This chemical cocktail often includes noxious or corrosive substances like hydrochloric acid, benzoquinones, and hydrogen cyanide. In some species, the secretions contain powerful sedative alkaloids, such as quinazolinones.
For a non-adapted spider, contact with these secretions can be devastating, potentially causing prolonged immobilization. Specialized spiders, however, employ sophisticated counter-adaptations to bypass this chemical warfare. The cellar spider’s strategy is to rapidly bind the millipede in dense sheets of silk, restraining the prey until the noxious secretions have dissipated or preventing the millipede from coiling and releasing the chemicals.
Other spiders use a highly precise anatomical attack, targeting the vulnerable, soft intersegmental membranes between the millipede’s armored rings. By piercing these soft joints, the spider can inject its venom without contacting the tough exoskeleton or triggering a full chemical release. This focused attack minimizes the exposure to defensive compounds and ensures the venom reaches the millipede’s nervous system quickly, before the potent secretions can be deployed effectively.