''Eutrichodesmus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

millipede Millipedes (originating from the Latin , "thousand", and , "foot") are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derive ...

s in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Haplodesmidae. Containing 54 species, this genus is among the genera with the greatest number of species not only in the family Haplodesmidae but also in the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Polydesmida Polydesmida (from the Greek ''poly'' "many" and ''desmos'' "bond") is the largest order of millipedes, with more than 5,000 species, including all the millipedes reported to produce hydrogen cyanide (HCN). This order is also the most diverse of ...

. This genus includes the species '' E. peculiaris'', notable for featuring

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

in segment number: The adult females have 20 segments (counting the collum as the first segment and the

telson The telson () is the hindmost division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment (biology), segment of the arthropod body, or an additional division that is not a true segm ...

as the last), but the adult males have only 19 segments. Millipedes in this genus are found in southern

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

, southern

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, mainland

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

, and

Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (; ), is an island country in Melanesia located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of northern Australia, northeast of New Caledonia, east o ...

Description

Millipedes in this genus are small, ranging from 3.5 mm to 14 mm in length. These millipedes can have 19 or 20 segments. Species in this genus are capable of

volvation Volvation (from Latin ''volvere'' "roll", and the suffix ''-(a)tion''; sometimes called enrolment or conglobation), is a defensive behavior in certain animals, in which the animal rolls its own body into a ball, presenting only the hardest parts ...

, which is usually complete but sometimes incomplete. The basal element of the

gonopod Gonopods are specialized appendages of various arthropods used in reproduction or egg-laying. In males, they facilitate the transfer of sperm from male to female during mating, and thus are a type of intromittent organ. In crustaceans and millipe ...

(coxa) in adult males in this genus usually features abundant

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

e. The distal element of the gonopod (telopodite) is usually slender and long, with dense setae on the basal half. The telopodite often features a conspicuous outgrowth on the lateral side. The distal part of the telopodite is conspicuous and well developed but rarely branches into a separate lobe. The millipedes in this genus resemble those in the genus ''

Doratodesmus ''Doratodesmus'' is a is a genus of flat-backed millipedes in the family Haplodesmidae. These millipedes are found in China, Indonesia, and Papua New Guinea. This genus includes two species that are notable for including adult males with only 1 ...

'', which are also capable of volvation. Like the adult males in ''Eutrichodesmus'', those in ''Doratodesmus'' also usually feature gonopod coxae with abundant setae. The adult males in ''Doratodesmus'', however, feature gonopod telopodites that are usually stout and markedly enlarged toward the sides, unlike those usually observed in ''Eutrichodesmus'', which are slender.

Species

This genus includes the following species: * ''

Eutrichodesmus arcicollaris ''Eutrichodesmus'' is a genus of millipedes in the family Haplodesmidae. Containing 54 species, this genus is among the genera with the greatest number of species not only in the family Haplodesmidae but also in the order Polydesmida. This genu ...

'' Zhang, 1993 * ''

Eutrichodesmus armatocaudatus ''Eutrichodesmus'' is a genus of millipedes in the family Haplodesmidae. Containing 54 species, this genus is among the genera with the greatest number of species not only in the family Haplodesmidae but also in the order Polydesmida. This genu ...