Myriapods (Myriapoda) Chapter 7.2

Alien myriapods in Europe have never been subject to a comprehensive review. Currently, 40 species belonging to 23 families and 11 orders can be regarded as alien to Europe, which accounts approximately for about 1.8% of all species known on the continent. Millipedes (Class Diplopoda) are represented by 20 alien species, followed by centipedes (Class Chilopoda) with 16, symphylans with 3 and pauropods with only 1. In addition there are numerous cases of continental species introduced the Indian Ocean. Ten myriapods are of unknown origin (cryptogenic). Only 12 species ( ca. 30%) of all have established in the wild in Europe. At the present time alien myriapods do not cause serious threats to the European economy and there is insuffi cient data on their impact on native fauna and fl ora.


Introduction
Myriapods are terrestrial wingless arthropods with elongated bodies composed of more or less similar segments, most of which bear one or two pairs of legs. Four classes are recognised: Pauropoda, Symphyla, Chilopoda and Diplopoda. Approximately 15 000 species from nearly 160 families are currently known in the world. Th e Diplopoda is by far the most diverse group, comprising roughly 11 000 species (Adis and Harvey 2000). A total of 2,245 m yriapod species or subspecies from 15 orders and 70 families are currently known in Europe (http://www.faunaeur.org/statistics.php), of which 1,529 are Diplopoda, 481 Chilopoda, 41 Symphyla and 125 Pauropoda. All members of the class Diplopoda (millipedes) have two pairs of legs per diplosegment for most segments. Several morphotypes have been recognised, i.e. juloid, polydesmoid, polyxenoid, platydesmoid and glomeroid (Kime and Golovatch 2000), of which the former two are especially rich in species both in Europe and worldwide. Most of the species are cylindrical or fl attened dorsally, often with prominent lateral projections, generally medium-to large-sized (up to 8-9 cm in the genera Pachyiulus and Eurygyrus). Some species of the order Glomerida, or pill millipedes, are oniscomorph, capable of rolling up into a tight ball. Members of the order Polyxenida, or "dwarf millipedes", are minute in size and with peculiar hairs along the body arranged in groups and tufts like small pin-cushions or brushes. Th e number of legs varies between species, often (especially in juloids) even individually, the record being 375 pairs in the North American siphonophoridan species Illacme plenipes Cook &Loomis, 1928 (Marek andBond 2006). Species of the class Chilopoda (centipedes) have an elongated fl attened trunk and bear one pair of legs per segment, with a total number ranging between 15 and 191 pairs. Centipede body length varies from a few millimeters in some species of genus Lithobius (Monotarsobius) to approximately 30 cm in the Neotropical species Scolopendra gigantea (Minelli and Golovatch 2001). All centipedes have a pair of poison claws, or forcipules, which represent modifi ed fi rst body appendages. About 3,500 valid species and subspecies from 5 orders and 22 families are known in the world (Minelli 2006, Edgecombe andGiribet 2007). Th e other two myriapod classes -Symphyla and Pauropoda -consist of very small species, with body length of 2-8 and 0.5-1.9 mm respectively, both still remaining very poorly studied. Th e number of described symphylans and pauropods in the world is roughly estimated to about 200 and 700, respectively (Adis and Harvey 2000).
Centipedes are mostly predatory, feeding on diff erent available prey items in the soil (earthworms, enchytraeids, snails, slugs, small insects -both larvae and adultsand other arthropods). More details on the biology and ecology of millipedes, centipedes and the two other, smaller myriapod classes can be found in Hopkin and Read (1992), Lewis (1981), and Verhoeff (1933Verhoeff ( , 1934. Little information is as yet available on the non-indigenous myriapods in Europe (DAISIE 2009, Roques et al. 2009). Th e most recent overview of alien organisms in Europe (see DAISIE 2009, p. 225) lists two centipedes (Lamyctes emarginatus, Lamyctes caeculus) and three millipedes ( Oxidus gracilis, Eurygyrus ochraceus, Sechellobolus dictyonotus = Paraspirobolus lucifugus) as alien to Europe. Some papers have been, however, published on the ecology, morphology and post-embryonic development of several alien centipedes (Andersson 1984, Bocher and Enghoff 1984, 1975a, Negrea 1989) and millipedes (Enghoff 1975b, 1978. Lists of alien species have been published for a few countries only, such as Germany (Kinzelbach et al. 2001), Austria (Gruber 2002, Gruber andChristian 2002), the Czech Republic (Šefrová and Laštůvka 2005), Switzerland (Wittenberg 2005), Italy (Zapparoli and Minelli 2005) and Great Britain (Barber 2009a, b). Increasing attention has been paid in the last decades to species which have accidentally arrived in Europe (see Barber 2009a, BBC News 2005, Christian and Szeptycki 2004, Gregory and Jones 1999, Lewis 1988, Lewis and Rundle 1988 for centipedes and Andersson and Enghoff 2007, Enghoff 2008aand Read 2008 for millipedes).

Taxonomy of the myriapod species alien to Europe
Altogether, 40 species belonging to 23 families and 11 orders can be regarded as alien to Europe (Table 7.2.1). Th is accounts approximately for about 1.8% of all myriapods known on the continent. Millipedes are represented by 20 alien species, followed by centipedes with 16, symphylans with 3 and pauropods with only 1. Th e relative proportion of alien species is highest in Symphyla (7.3%) and Chilopoda (3.3%), and the lowest in Pauropoda (0.8%) and Diplopoda (1.3%). Th e centipede family Henicopidae is the richest in alien species (5 species), followed by Scutigerellidae, Mecistocephalidae, Scolopendridae, Paradoxosomatidae and Pyrgodesmidae, each with three species. Th e remaining 17 families are represented by only one or two species each (Figure 7.2.1). Striking is the absence of alien species in Europe of the species-rich order Spirostreptida since spirostreptidans, for instance Hypocambala anguina (Attems, 1900) and Glyphiulus granulatus Gervais, 1847, are quite widespread in the tropical countries and show a clear tendency to anthropochorism (Jeekel 1963, Shelley 1998. Several myriapods have been intercepted at their arrival in Europe from consignments from other countries but have never managed to establish themselves. Barber (2009a) provided a list of centipede species captured and registered by the Central Science Laboratory (now FERA) in the UK when imported with exotic plants, fruits and luggage (Table 7.2.2). Two of them, Lithobius forfi catus and L. peregrinus, are European natives which have long been introduced to Australia and New Zealand, so their interception in Great Britain is a clear case of re-introduction.
A similar list for intercepted millipedes examined by the Central Science Laboratories between 1975 and 2006 (S. Reid pers. comm.) is more substantial with some 85 entries over this period of time (Table 7.2.2). Of these 36 were records of Oxidus gracilis from a wide range of diff erent parts of the world (W & S. Europe, Canary Islands, Israel, N., C. and S. America, Australia, China, Japan, Malaysia, Singapore, India, Nepal, N., W. and S. Africa and Madagascar). Other types found included members of the Polydesmida (dalodesmids, parodoxomatids, polydesmids), Spirosteptida (from Australia, New Zealand and Africa), Julidae and Blaniulidae. Amongst species from the latter two families were the NW European Blaniulus guttulatus and Cylindroiulus londinensis (both from Australia) and Ommatoiulus moreletii (originating in the Iberian Peninsula, introduced to Australia in 1953 and now a pest species there; in this list reported from both that country (tree fern) and South Africa (melon fruit)).
Man-aided introductions of species from one part of Europe to another have played a prominent role. One of the most common synanthropic centipedes in North Europe is the Mediterranean "house centipede" Scutigera coleoptrata (Linnaeus, 1758). It has been introduced to a number of North European cities, e.g., Copenhagen, Edinburgh, Aberdeen, Leiden, etc., where it survives only in buildings. Th e earliest record in the British Isles of this species is perhaps that by Gibson-Carmichael (1883) who recorded it from a paperworks near Aberdeen. It could have been established there already for 25 years and arrived in bundles of rags from South Europe (Barber 2009a); at the present time it is sporadically reported from inside buildings in various parts of Britain and seems to be common in houses in St. Peter Port (Guernsey) and St. Helier (Jersey) in the Channel Islands from where it has also been reported from outdoor sites. Other cases of south or central European species being introduced to northern countries that perhaps still survive only in buildings, hothouses, gardens or similar man-made habitats are: Tuoba poseidonis (Verhoeff , 1901) in Finland, Dicellophilus carniolensis (C.L. Koch, 1847), Lithobius lucifugus L. Koch, 1862, Lithobius peregrinus Latzel, 1880, Haplopodoiulus spathifer (Brölemann, 1897 and Cylindroiulus salicivorus Verhoeff , 1908in Great Britain, Cylindroiulus vulnerarius (Berlese, 1888 in Sweden, Pachyiulus varius (Fabricius, 1781) in Norway, etc. (Barber 1995, Barber and Eason 1986, Barber and Keay 1988, Bergersen et al. 2006, Lee 2006, Read 2008. Even within the same geographic area some indigenous species occur at localities that are not part of their primary distribution area, most probably as a consequence of accidental anthropogenic introductions. Examples are the records from Italy of Lithobius infossus Silvestri, 1894 near Padua (Minelli 1991), of L. peregrinus Latzel, 1880 in northeastern and central Italy (Minelli 1991, Zapparoli 1989, Zapparoli 2006, of Pleurolithobius patriarchalis (Berlese, 1894) in the Egadi, Pontine and Campania islands (Zapparoli and Minelli 1993), and of Scolopendra cingulata near Milan (Manfredi 1930).
Island invasions by continental species is another phenomenon worth mentioning. Eason in a study on the Icelandic fauna, concluded that most centipede and millipede species probably arrived by human transport (Eason 1970). Examples of recent introductions to Iceland are Geophilus truncorum Bergsøe & Meinert, 1866, Polydesmus inconstans Latzel, 1884, and Brachydesmus superus Latzel, 1884, which "… have only been found on Heimaey, one of the Vestman Islands, which supports a town and where casual introduction by human transport is likely: they have probably been introduced quite recently and the two millipedes seem still to be confi ned to the outskirts of the town". Regarding the other two possibly allochthonous species, Lithobius forfi catus (Linnaeus, 1758), and Lithobius erythrocephalus C.L. Koch, 1847, Eason wrote, "these two species may be confi ned to the south owing to the relatively warm and humid southern climate, but their restricted distribution might also be explained by their having been introduced by Norse settlers ....". Th e fi rst Norse set-tlements on Iceland were established in the ninth century A.D., so this must have happened after that time.
According to Enghoff (2008b), of the 21 species of centipedes recorded in Madeira 17 are introduced and 2 are probably introduced. High rates of introduction are also known for the Azores and Canary Islands Enghoff 2005, Zapparoli andOromi 2004) (Table 7.2.3). All symphylans on the Canary Islands have been considered as possibly introduced. Likewise, only two of 21 millipede species are considered native on the Azores .
Th e geophilomorph centipede Nyctunguis persimilis Attems, 1932 was originally described from Turkey and has not been found there since in spite of the active work of the second author who has published several papers on the Turkish centipede fauna during the last 20 years. Taking into account that the species was recently found in synanthropic habitats in the outskirts of Vienna (Christian 1996) and that all other congeners occur in the Nearctic region, it is very likely that the type locality (the surroundings of Ankara, Turkey) is erroneous and the material was actually mislabeled (Zapparoli 1999).
Mecistocephalus maxillaris (Gervais, 1837), one of the fi rst alien centipedes to be recorded in Europe, is another poorly known species. It was described from the gardens of the Muséum National d'Histoire Naturelle, Paris, and subsequently recorded from numerous places around the world. However, most of the records were certainly based on misidentifi cations with the morphologically similar M. guildingii or M. punctifrons actually being involved (Bonato et al. 2009). According to Bonato et al. (2009), most of the records in Europe e.g., those from Germany, Great Britain, France (not the type specimen but material taken subsequently from a greenhouse in the Paris Museum, cf. Brolemann 1930) and Portugal (Madeira), are referable to M. guildingii, while those from the Netherlands and Denmark require further clarifi cation.
Th e actual taxonomic status and native range of Ghilaroviella cf. valiachmedovi remains uncertain. Th e same applies to the millipede Chondrodesmus cf. riparius which shows some diff erences from the original description by Carl (1914) and its identity cannot be clarifi ed without a comprehensive review of the entire genus (Enghoff 2008a).

Temporal trends in the introduction of alien myriapod species to Europe
Introductions of alien myriapods into Europe probably began several centuries ago, even though a precise arrival date is hard to determine. Only 10 out of 40 species were recorded for the fi rst time in Europe in the 19 th century while most of the records date from the 20 th (26 species) and 21 st centuries (4 records).
Gervais was virtually the fi rst person to record alien myriapods in Europe (Gervais 1836(Gervais , 1837. He described the tropical millipede Iulus lucifugus (now Paraspirobolus lucifugus) and the geophilomorph centipede Mecistocephalus maxillaris from greenhouses of the Paris Museum. Th e means of arrival of both species remains obscure but must be linked to the establishment of the greenhouses and the planting of tropical fl owers, perhaps already by the end of the 18 th century. P. lucifugus has been subsequently recorded in intervals of around 60-70 years from greenhouses near Hamburg (Latzel 1895), Hortus Botanicus Amsterdam (Jeekel 1977), a greenhouse in Copenhagen (Enghoff 1975b), and more recently from the Tropical Biome at the Eden project (Lee 2006). Th is can hardly be regarded as refl ecting the actual course of colonization but rather the date of investigation and the level of eff ort involved in each case.
Th e only alien millipede that has invaded some natural ecosystems in Europe and acclimatized is the East Asian species Oxidus gracilis. Perhaps the earliest records of this species in Europe are those of Tömösváry (1879) from the Margaret Island in Danube, Hungary, and of Latzel (1884) from greenhouses in Zeist, Utrecht, and Amsterdam in the Netherlands. Subsequently it was also found in Edinburgh in 1898 and in Kew Gardens in Great Britain (Evans 1900, Pocock 1902). In Finland the species was fi rst recorded in 1900, but since the sample already contained several specimens the species must have arrived there at least two years earlier (Palmén 1949). Th e mechanism of dispersal of the species within Europe is certainly related to the trading and growing of tropical plants in the greenhouses as in some places this process must have happened more than once. According to Palmén (1949), the population of O. gracilis in the greenhouses of Hanko, South Finland went extinct during the period 1939-1943 when they were not kept warm. In 1946 a single female was found in a greenhouse with plants imported from Belgium, in 1947 its numbers increased considerably and the next year it was already very abundant in the whole greenhouse complex. Golovatch (2008) suggested that the intense trade ties between the ancient town of Khersonesos in the Crimea and the town of Pergam (= Bergama), a major centre of red ceramics production of the time in present-day Turkey, as possible pathways for the introduction of Eurygyrus ochraceus in the Ukraine. He also pointed out that the Bulgarian population near Varna may owe its origin to the very active commerce in Roman times between Bergama and the colonies in Moesia (= currently northern Bulgaria and southern Romania), including Odessos (= Varna). Th e area and trade connections were already quite developed by the mid-4 th century B.C. or even earlier, under ancient Greeks, so this introduction must have happened around that time.
Members of the genus Lamyctes are represented in Europe only by parthenogenetic populations. Males of L. emarginatus are known only from Macaronesia, New Zealand, Tasmania and Hawaii (see also Attems (1935) and Zapparoli (2002) for the record of a single male from Greece), while males of L. coeculus are only known from a greenhouse in Italy and from Cuba (Enghoff 1975a). Taking into account that the entire family Henicopidae is predominantly distributed in the Southern Hemisphere, and presuming that the regions where males are being found are the native areas of the species, L. emarginatus could have been introduced to Europe from one of the above regions, most likely from Australia or New Zealand. Th e earliest confi rmed record is from Denmark in 1868 (see Meinert 1868). Lamyctes coeculus was fi rst found in a greenhouse in Italy at the end of 19 th century (Brölemann 1889), but its presence in the area would have been older. It has been recently found in Great Britain (Barber 2009b).
Th e earliest records of Cylindroiulus truncorum in Europe date from the 1920's and, according to Schubart (1925), the Central European populations are probably of relatively recent origin. In Finland it was fi rst reported in 1945 and in the following three years its numbers increased considerably. It is completely lacking in older collections (Palmén 1949).
One of the recent introductions is the large Neotropical millipede Chondrodesmus cf. riparius which was fi rst recorded in 2000 in a fl owerpot in the telephone offi ce of Umeå University, northern Sweden. It was found again elsewhere in Sweden in 2006 and, later, in January 2007, it was also recorded in a fl owerpot with a palm (Phoenix robbelini) in an offi ce in Copenhagen and in a fl owerpot in Bonn (Enghoff 2008a). Th ere are further records of the species from fl owerpots in Germany and also a recent one in Norway (Göran Andersson in litt.), so it seems that the species is dispersing well with palm pots.
Th e study of the invertebrate fauna of Kew Gardens, Great Britain began already at the beginning of 20 th century with papers by Pocock (1902Pocock ( , 1906 and continues today (Blower and Rundle 1980, Read 2008. Some of the species recorded by Pocock such as Scolopendra morsitans, Trigoniulus corallinus and Asiomorpha coarctata have not been re-found since then and most likely could not become established in Kew Gardens. At the same time Paraspirobolus lucifugus, Amphitomeus attemsi, Cylindrodesmus hirsutus, Rhinotus purpureus and Pseudospirobolellus avernus, species not previously known from Britain have been recorded recently in the Tropical Biome at the Eden project in Cornwall (Read 2008, Barber 2009b, Barber et al. 2010.

Biogeographic patterns of the myriapod species alien to Europe
Records of exotic species are not evenly distributed in Europe but this is mainly due to the diff erent levels of investigation of this area. Th e highest number of species (25) has been recorded from Great Britain, followed by Germany with 12, France with 11 and Denmark with 10 alien myriapods (Figure 7.2.2). In general, northern and economically more developed countries with high levels of imports and numerous busy sea ports are richer in alien species. Th ese countries also, in general, have poorer native faunas meaning that a small number of aliens can constitute a large percentage of the fauna. Several species are hitherto known in Europe from a single country only, e.g. Prosopodesmus panporus, Pseudospirobolellus avernus, Tygarrup javanicus and Cryptops doriae, which implies recent introductions or poor dispersal abilities. Others, such as Eurygyrus ochraceus, Paraspirobolus lucifugus and Lamyctes coeculus, have a larger but yet fairly restricted distribution limited to two or more countries. Th e most widespread species are the parthenogenetic centipede Lamyctes emarginatus, whose range in Europe spreads from the Urals to Iceland [outdoor species], and the bisexual millipede Oxidus gracilis, reported from 33 countries, including several Mediterranean islands.
Th e various alien myriapods have diff erent origins, but most of them show tropical or subtropical links (28 species, 70%). Eight of them (20%) are widespread in the Tropical and Subtropical belts, very often introduced by human agency to islands and synanthropic areas on continents. Th eir native range cannot so far be determined with certainty (Figure 7.2.3). Eleven (circa 28%) alien myriapods are of Asian origin, the majority (10 species) having their native range in East or Southeast Asia, and only one from West Asia, namely Anatolia. Cylindroiulus truncorum is perhaps the only North African myriapod introduced to Europe just as Brachyiulus pusillus (Leach, 1814) so far is the only European julid introduced to North Africa (Akkari et al. 2009). Th e only species that seems to be an Australasian native (Australia and New Zealand) is Lamyctes emarginatus. Among henicopids, Rhodobius lagoi and Ghilaroviella cf. valiachmedovi are of particular interest being members of monotypic genera and the only representatives in Europe of the subfamily Anopsobiidae which comprises chiefl y species with Gondwanan distribution patterns. Besides Rhodobius, four other monotypic genera represent the subfamily in the Northern Hemisphere, occurring in Vietnam, Japan, Kazakhstan, and Tajikistan (Edgecombe 2003, Farzalieva et al. 2004. Of Central or South American origin are seven species (circa 18%), and one each from North America and islands in Indian Ocean. Th e sole record of the pantropical geophilomorph centipede Orphnaeus brevilabiatus in Europe comes from Bohuslän, a Swedish province in the northern part of the W coast, where the animal was collected in the 19 th century (Andersson et al. 2005).
Ten centipedes and millipedes have been considered as cryptogenic (= species of unknown origin which cannot be ascribed as being native or alien). Some of them such as the geophilid Arenophilus peregrinus and the schendylid Nyctunguis persimilis, which have only been reported from the Isles of Scilly, Great Britain and Austria respectively (Barber 2008, Christian 1996 whereas all the other species of these genera live in North America, are of likely Nearctic origins. Another suspected introduction of uncertain origin is Nothogeophilus turki which has hitherto been known only from Scilly and the Isle of Wight, Great Britain ) and represents a monotypic genus. However, we cannot completely exclude the possibility that some cryptogenic species suspected to be alien are actually native to Europe. Support for this notion we fi nd in the scolopendromorph centipede Th eatops erythrocephalus C.L. Koch, 1847, which occurs in various natural habitats (including caves) in the Pyrenees and the western part of the Balkans (with a gap between these geographic areas), while all its other four congeners occur in North America (Minelli 2006).
Unknown also is the origin of the symphylid Hanseniella oligomacrochaeta described from a hothouse in the Botanical Garden in Berlin; according to Scheller (2002), all species in the genus Hanseniella have tropical-subtropical distributions. Th e haplodesmid Prosopodesmus panporus is only known from the Royal Botanic Gardens in Kew, England, while its other described congener, P. jacobsoni Silvestri, 1910, is pantropical ). Likewise, it is uncertain whether Napocodesmus endogeus, a millipede described solely from females collected in the garden of Cluj University, is a European native or not. According to Tabacaru et al. (2003), the generic allocation of the second species described in the genus, N. fl orentzae Tabacaru, 1975, hitherto known from Romania and Moldova, is not certain and since there are no other records of N. endogeus in nature it might be an introduced species.

Pathways for the introduction of alien myriapod species in Europe
All of the alien myriapods have most probably been accidentally introduced to Europe with plant material in relation to human activities and trade between Europe and other continents such as Asia, Australasia and the Americas. Th is process must have begun with an increase in trade between ancient Greek and Romans with cities in Asia Minor and North Africa and should have intensifi ed in post-medieval times with the trade between Europe and some East Asiatic countries (e.g. Japan, China) and the geographic discoveries of the Americas and, later, of Australia. Th is process is still going on with Th e distribution of the alien diplopods in Europe shows that all the species living here in greenhouses are much more widespread compared to e.g. the restricted outdoor species Eurygyrus ochraceus. It is also likely that the obligate thelytokous parthenogenesis (= sexual reproduction giving rise to females only) shown in continental Europe by several of the exotic millipedes and at least one of the centipedes has facilitated their survival during transport and their establishment on the continent. However, bisexual populations are known from the Azores and the Canary Islands for Lamyctes emarginatus (Enghoff 1975a). Species from other centipede orders, such as the mecistocephalid Tygarrup javanicus also presumably reproduce by parthenogenesis since so far only females have been found in the hothouse at the Eden project, in Great Britain (Barber 2009b).
Th e number of exotic diplopods in Europe is far smaller (3-4 times) than that of European species introduced to other continents. Apparently, this could mean that the arrival and, especially, becoming resident in Europe is much more diffi cult than the converse process. Th e asymmetry has probably nothing to do with quarantine controls at European borders. Instead, it may be due to specifi c ecological and biological patterns exhibited by the successful invaders. Many of the alien millipedes and centipedes which have successfully invaded Europe be- long to genera moderately rich to rich in species, such as Poratia, Chondrodesmus, Lamyctes, Cryptops, etc. A pertinent question arises as to why often only one species succeeds in establishing populations on foreign continents, sometimes becoming quite widespread to even cosmopolitan, whereas its rather numerous congeners fail to do so. Specifi c adaptive ecological patterns may be an issue, but, as noticed    above, obligate or opportunist parthenogenesis is probably a major trait favoring dispersal at least because a single founder juvenile or female is suffi cient to arrive at destination and found a population. It has to be noted that the successful myriapod invaders tend to be among the smallest species, thus being more easily transported, better fi tted to fi nd a suitable microhabitat, and sometimes requiring a shorter time and even a smaller number of developmental stages to reach maturity (Golovatch 2009).  Another possible pathway of the introduction of exotic myriapods to Europe is their intentional import as 'pets', and their further escape from pet keepers. Large Scolo pendra spp., as well as some large and colorful millipedes of the orders Spirobolida, Spirostreptida and Sphaerotheriida are quite popular pet animals subjected to trade in pet shops. Although there are many guides and internet resources available for keeping and caring for exotic species, there is no reliable information about the importance of the 'pet' trade for the introduction of alien myriapods to Europe. However, the establishment of pet myriapods in the wild is in most cases very unlikely.

The most invaded ecosystems and habitats
Man-made artifi cial environments (pastures and cultivated lands, greenhouses, urban and suburban areas) constitute the main habitat types hosting alien myriapods (Table 7.2.1). Species of tropical and subtropical origin are likely to be restricted to greenhouses or equivalent artifi cially warmed habitats. Some of them, in the summer season in the southern countries perhaps could survive also outdoors in close proximity to the hothouses. However, 11 species have been reported from natural habitats in Europe, where they most likely were able to establish viable populations. So far the alien species of symphylans and pauropods are unknown in natural areas, which is not the case with several species of the other two myriapod classes. Th e millipede Oxidus gracilis, which is bisexual everywhere and is naturalized in several areas in Europe and in the Caucasus, has been found in forests close to suburban and urban areas (Tömösváry 1879), in woodlands of Robinia pseudoacacia in the Kanev Nature Reserve, Ukraine  (Chornyi and Golovatch 1993) and records from caves also exist (Strasser 1974, Vicente andEnghoff 1999). On the Canary Islands the species is quite widespread invading various, mostly dry and warm, habitats ). According to Palmén (1949), O. gracilis dies when subjected for 2 hours to a temperature of minus 4°C. Th is means that in North Europe the species can survive only in hothouse conditions. Cylindroiulus truncorum mainly inhabits synanthropic habitats: greenhouses, gardens, parks, woodpiles, school grounds, cemeteries, spoil heaps, horticultural nurseries (Kime 2004, Korsós andEnghoff 1990).
Eurygyrus ochraceus occurs in the Crimea only in a patch of semi-natural xerophytic vegetation ca. 1 km long and 100-300 m wide along a watershed. It was reported to be rather common, although not too abundant on the site and is defi nitely an anthropochore (Golovatch 2008).
Lamyctes emarginatus shows remarkable plasticity regarding the surrounding environment, although in the British Isles there is preponderance of rural records in comparison with (sub)urban ones. In artifi cial habitats it has been reported from gardens, roads, roadside verges, hedges, embankments, crops of Zea mays and Medicago sativa, even in human rubbish (Eason 1964, Minelli and Iovane 1987, Barber and Keay 1988. In natural habitats it lives in various woods (deciduous or mixed coniferous/ deciduous) and has also been recorded from open and coastal areas (Barber and Keay 1988, Zerm 1997, Zapparoli 2006. According to Andersson (2006), it predominates in open and disturbed areas with sparse vegetation. A great many of these localities are associated with lake shores, river gravels or river banks. L. emarginatus shows clear preferences for temporarily fl ooded sites, no matter for how long the inundation lasts. Its appearance as a pioneer species on mine sites may indicate that the species shows preference to disturbed habitats (Zerm 1997). In close proximity to water pools the species abundance can reach 95% of all centipedes (Minoranskii 1977).
Two of the (presumed) alien geophilomorphs, Arenophilus peregrinus and Nothogeophilus turki, have been recorded in coastal areas, where they occur under stones and in soil close to rocky sea cliff s with sparse vegetation although A. peregrinus has been found inland in Cornwall in woodland and one of the Isle of Wight records for Nothogeophilus turki was from an area of demolished buildings with copious rubbish on the ground although no more than 5 m from the tidal river (A.N. Keay pers. comm.).
Considerable fl uctuation in the abundance of some alien species have been observed by Barber (2009b)

Ecological and economic impact
Alien myriapods are unlikely to pose major threats to native biodiversity and ecosystems. Th e number of species established in the wild being very limited (12 species, ca 30%) for the moment (Table 7.2.1). Diplopods are detrivorous animals, consuming 10-15% of the leaf litter in temperate forest and as thus contribute signifi cantly to soil formation processes through the fragmentation of leaves which stimulates microbial activity. Th ey may thus indirectly infl uence the fl uxes of nutrients (Hopkin and Read 1992). Nevertheless, some alien diplopods could be harmful to cultivated plants, especially in the artifi cial habitats where temperature and humidity conditions allow species establishment and expansion. Invasive soil invertebrates may also have an impact on the structure and function of natural ecosystems. Th ey can change soil carbon, nitrogen and phosphorus pools and can considerably aff ect the distribution and function of roots and micro-organisms (Arndt and Perner 2008). In addition, mass occurrences and swarming, which have been observed in several countries in Europe, may have negative ecological and economic impact although the causes still remain obscure (Sahli 1996, Voigtländer 2005). An example of a plant-damaging alien myriapod is Oxidus gracilis, which is regarded as a pest in several European countries. Th is species is very common in greenhouses where its density may exceed 2500 ind./ m 2 . It is known for attacking vegetable and fruit crops such as sugar beet, potatoes, strawberries, cucumbers, orchard fruits, roots of wheat, and fl owers in outdoor cultivated areas. Furthermore, several thousand O. gracilis were once found after rain in a house in Lenoir City, Tennessee, USA, with most of the city infested during the same outbreak (Hopkin and Read 1992). As a curiosity, one might also mention the report by the classical writer Th eophrastus, according to whom an army of millipedes once overran Rhoeteum in the present province of Çanakkale (northwestern Turkey) and drove its human inhabitants into the sea (Sharples 1994, Enghoff andKebapći 2008).
Several plants can withstand the attacks of symphylans but they may cause severe damage to growing crops both in fi elds and greenhouses (Scheller 2002). Arndt and Perner (2008) recently carried out a study on the impact of invasive ground-dwelling predatory species, including alien centipedes, in the native laurel forest habitat in the Canary Islands. Th ey found that centipedes in laurel forests seem to be much more variable than carnivorous ground beetles since the 14 recorded species include representatives of three orders with very diff erent characters. Th ey tentatively recognised four functional groups of centipedes: a micro-cephalic schendylid type, (ii) a geophilid type with medium head size and extreme body length, (iii) a scolopendromorph type, and (iv) a macro-cephalic lithobiomorph type. Th ese groups suggest patterns of invasion similar to the coleopteran predators: autochthonous and introduced species of the same size class and group are mutually exclusive (Arndt 2006).