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Concept
Symphyla
Résumé
Symphylans, also known as garden centipedes or pseudocentipedes, are soil-dwelling arthropods of the class Symphyla in the subphylum Myriapoda. Symphylans resemble centipedes, but are very small, non-venomous, and only distantly related to both centipedes and millipedes. They can move rapidly through the pores between soil particles, and are typically found from the surface down to a depth of about . They consume decaying vegetation, but can do considerable harm in an agricultural setting by consuming seeds, roots, and root hairs in cultivated soil.
Juveniles have six pairs of legs, but over a lifetime of several years, they add an additional pair at each moult so an adult instar usually has twelve pairs of legs. Most adult symphylans have twelve leg pairs, but the first pair is absent or vestigial in some species (e.g., those in the genus Symphylella), so adults in some species have only eleven leg pairs. Symphylans lack eyes. Their long antennae serve as sense organs. They have several features linking them to early insects, such as a labium (fused second maxillae), an identical number of head segments and certain features of their legs.
About 200 species are known worldwide.
Symphyla are small, cryptic myriapods without eyes and without pigment. The body is soft and generally long, divided into two body regions: head and trunk. An exceptional size is reached in Hanseniella magna, which attains lengths of .
The head has long, segmented antennae, a postantennal organ, three pairs of mouthparts: mandibles, the long first maxillae, and the second pair of maxillae which are fused to form the lower lip or labium of the mouth. Disc-like organs of Tömösváry, which probably sense vibrations, are attached to the base of the antennae, as they are in centipedes.
The trunk comprises 15–24 segments, which are protected by overlapping dorsal plates. Ten or twelve segments bear legs. The first segment is large and usually provided with a pair of legs, the last segment is slender, lacks legs, and possesses a pair of cerci.
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