The cylindrical millipedes of the order Julida are masters of temperate forest floors

Nature · Published 3 October 2026 Swipe more like this →

In short: Spanning from North America to the mountains of Asia, the order Julida comprises roughly 750 species of millipedes. These small, cylindrical creatures possess unique anatomical features that distinguish them from other arthropods, including specialized leg modifications in males that play a critical role in their complex reproductive biology and survival.

The order Julida represents a diverse group of millipedes characterized by their elongated, cylindrical body shapes. These arthropods are generally small, with individual lengths typically falling between 10 and 120 millimetres. While some species have developed eyes, others have evolved to live without them, reflecting their adaptation to various subterranean or leaf-litter environments across the temperate regions of the Northern Hemisphere.

A defining characteristic of this order is the specialized anatomy found in mature males. In many species, the first pair of legs is transformed into distinct hook-like structures. Even more specialized are the legs located on the seventh body segment; both pairs are modified into gonopods. These structures are essential for the reproductive process, serving as specialized appendages for sperm transfer, which highlights the evolutionary complexity hidden within these seemingly simple invertebrates.

Geographically, Julida is predominantly found in temperate zones. Their range is vast, stretching from North America down to Panama, and across Europe and Asia, including regions north of the Himalayas, the Asir region of Saudi Arabia, and parts of Southeast Asia. With approximately 750 species identified, the order remains a significant component of soil ecosystems, where they contribute to the breakdown of organic matter.

While these millipedes are often overlooked, their biological activity is multifaceted. Research into their secretions suggests that these creatures possess sophisticated chemical defenses, which likely protect them from predators and pathogens in their diverse habitats. Understanding the distribution and anatomy of Julida provides a clearer picture of how these arthropods have successfully colonized such a wide array of temperate environments across the globe.

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