Synopsis and identification of North American hairworms (Gordioidea: Nematomorpha).
Hair worms (Research)
Hair worms (Identification and classification)
Poinar, George, Jr.
Chandler, Clay M.
Pub Date:
Name: Journal of the Tennessee Academy of Science Publisher: Tennessee Academy of Science Audience: Academic Format: Magazine/Journal Subject: Science and technology Copyright: COPYRIGHT 2004 Tennessee Academy of Science ISSN: 0040-313X
Date: Jan, 2004 Source Volume: 79 Source Issue: 1
Event Code: 310 Science & research
Geographic Scope: North America Geographic Code: 100NA North America

Accession Number:
Full Text:
ABSTRACT -- The present work reviews the hosts, distributions, synonyms and taxonomic characters of North American hairworms (Gordioidea: Nematomorpha) and presents a key based on adult morphological characters that can be observed under the dissecting and light microscopes. A total of 18 described species are recognized in the present work. However the field is complicated by incomplete descriptions, lack of knowledge of morphological variation within species and sexual dimorphism.


Hairworms, or Gordioidea, are fresh water members of the Phylum Nematomorpha. These enigmatic organisms, which stand apart from other invertebrates, have been little studied due to their secretive habits, difficulty in rearing, lack of economic importance and problems regarding their identification. All known species develop in invertebrates, especially insects, but the larvae are capable of encysting (without development) in a wide range of animals, including vertebrates (Poinar, 2001; Schmidt-Rhaesa, 1997; Smith, 2001).

The present work reviews the hosts, distributions, synonyms and taxonomic characters used in the identification of North American hairworms and presents a key based on adult morphological characters that can be observed under the dissecting and light microscopes (Fig. 1).


First stage hairworm larvae are transparent and provided with an array of hooks, stylets and assorted devices for penetrating into the body cavity of potential hosts (Fig. 2-4). While these characters could be used for generic and even specific placement, too few larvae have been examined to make this method of identification practical. Thus only adult characters are used in identifying hairworms. Moreover, since the adults are normally opaque, only external characters are practical.

Diagnostic characters of adult hairworms include: 1) the presence and nature of the areoles (raised areas on the cuticle), especially their type, shape, size, arrangement, and association with pore canals, bristles, warts and papillae, 2) body shape, size and color pattern, especially that associated with the anterior (calotte) and posterior ends and, 3) features of the male tail, including first, whether it is simple or forked and then if it bears preor postcloacal ridges, folds, hairlines, bristle fields or tubercles. Caution should be taken since the adults frequently exhibit sexual and age dimorphism in relation to body size, shape and coloration as well as areole arrangement. In addition, fixation artifacts such as body ridges, folds, etc. may result from specimens remaining in alcohol for extended periods (the majority of hairworm species have been described from museum specimens that have been in preservative for a number of years). Unfortunately, the intraspecific variation of most diagnostic characters is unknown, since many species have been described from a single specimen or only one or two specimens have been examined in detail.

When available, scanning electron microscopy is a useful tool for studying fine details on the surface of hairworms. However this technique is not necessary for identification purposes if good light microscopes are available. Methods for preserving and preparing specimens for optical microscopic examination can be found elsewhere (Poinar, 2001; Smith, 2001).


Basically, all hairworms develop inside invertebrates, with a free-living stage in an aquatic habitat where mating and oviposition occur. Most, if not all, hairworms have an indirect life cycle, involving an aquatic paratenic host (Fig. 2-3) and a terrestrial (or rarely aquatic) developmental host (Fig. 2-1). The paratenic host (one that carries a parasite internally but does not support its growth or reproduction) ingests hairworm eggs containing preparasitic larvae or free-living preparasitic larvae in the water habitat. These preparasitic larvae enter the body cavity of the paratenic host by burrowing through the intestinal wall. Penetration is assisted by an extensible proboscis bearing circlets of spines as well as three stylets. After passing through the gut wall, the preparasitic stage then encysts, usually in the fat body, intestinal wall, connective tissue or muscle tissue of the paratenic host (Fig. 2-3). The range of paratenic hosts is more extensive than that of developmental hosts and can include fish, frogs and even humans. Presumably, chemical cues signal whether a host is suitable for development or encystment.

Growth and development of the hairworm larva occurs after the paratenic host is consumed and the hairworm larva enters the body cavity of a developmental (or definitive) host, usually an insect predator or omnivore. In some cases, instead of developing, the hairworm larva will re-encyst inside the predator. In this case, the predator becomes a secondary paratenic host (Fig. 2-3). When reporting hairworm hosts, it is important to state whether it is a paratenic or developmental host, which is not always clear from the literature (White, 1969).

A list of the 18 species of North American hairworms recognized in this work, and their synonyms, is given in Table 1. Available information on naturally occurring paratenic and developmental hosts of North American hairworms, along with notes on their distribution, is presented below, followed by a key to the adults. It should be noted that collection data on North American hairworms is quite sparse. Thus the geographic ranges presented below present a biased view of the actual range of species. It is likely that most North American hairworms occur throughout North America, but only in certain ecological habitats. Certain species, e.g. Gordius robustus and Paragordius varius, appear to be more widespread than others. Distribution depends on climatic and ecological conditions and available hosts. Environmental disruption by humans has a direct impact on hairworms and limits their occurrence to more remote habitats with natural water sources.


Chordodes morgani Montgomery, 1898a. This is essentially an eastern North American species with reports from as far south as Florida and as far west as Nebraska (Chandler, 1985). Montgomery (1898a) mentions that a blattid served as host to this species and Schmidt Rhaesa et al. (2003) reported Periplaneta fulginosa and Parcoblatta sp. as hosts. Studier et al. (1991) reported parasitism by this hairworm in the camel cricket, Ceuthophilus stygius and cave cricket, Hadenoecus subterraneus.

Gordionus densareolatus (Montgomery 1898a) nov. comb. has been reported from Western North America (Montgomery, 1907).

Gordionus lineatus (Leidy 1851) has been reported from eastern North America (Montgomery, 1898a, 1907; Leidy, 1851), including a cave in the Great Smoky Mountains National Park (Reeves, 2000).

Gordionus longareolatus (Montgomery 1898b) has only been reported from California (Montgomery, 1898b).

Gordionus platycephalus (Montgomery 1898a) has been reported from the Ungava Region of Eastern Canada, Montana, Penn-sylvania, Wyoming, Guatemala (Montgomery, 1898a, 1907) California and Utah (Poinar and Weissman, 2004) suggesting that it occurs throughout North America. Hosts include the orthopteran, Stenopelmatus spp. (Poinar and Weissman, 2004).

Gordionus sinepilosus Schmidt-Rhaesa et al., 2003 has been reported only from one locality in British Columbia.

Gordionus violaceus (Baird 1853) occurs throughout North America (Smith, 1991; Schmidt-Rhaesa et al., 2003).

Gordius alascensis Montgomery 1907, which was assigned to the genus Gordionus by Schmidt-Rhaesa et al. (2003), has been reported only from Alaska (Montgomery, 1907).

Gordius attoni Redlich 1980 has been reported from northern North America (Redlich, 1980; Schmidt-Rhaesa et al., 2003).

Gordius difficilis Montgomery 1898a (Smith 1994) has been reported from eastern North America (Smith, 1994). The ground beetles, Chlaenius prasinus (Coleoptera: Carabidae) and Pterostichus melanarius have been reported as developmental hosts for this species (Hanelt and Janovy, 2000; Bolek and Coggins, 2001).

Gordius robustus Leidy 1851 occurs throughout North America, including Mexico (Chandler, 1985; Camerano, 1915) and Hawaii (Montgomery, 1898a; Heinze, 1934). The North American developmental hosts for this species include various Acrididae (Ward and Whipple, 1918), Odonata (Cappucci, 1977), the orthopterans, Stenopelmatus fuscus Brunner (Cappucci, 1977), Stenopelmatus spp. (Poinar and Weissman, 2004), Anabrus simplex Haldeman (Thorne, 1940), Orchelimum nigripes Scudder (May, 1919), Orchelimum vulgare Harris (May, 1919), Scudderia furcata Brunner (May, 1919), Phaneroptera furcata (Brunner), (Thorne, 1940), Steiroxys sp. (Poinar and Weissman, 2004), Conocephalus nemoralis (Scudder), C. fasciatus (May, 1919), Gryllus sp. (Poinar and Weissman, 2004) and the carabid, Gastrellarius honestus Say (Leidy, 1856).

Neochordodes californensis de Miralles and de Villalobos 1995 has been reported only from California.

Neochordodes occidentalis (Montgomery 1898a) has been reported from western North America (Chandler, 1985), including Mexico (Poinar and Weissman, 2004). Developmental hosts include the orthopterans Stenopelmatus spp. and Pediodectes sp. (Poinar and Weissman, 2004). Ward and Whipple (1918) state that an acridid is also a developmental host, while mosquito larvae served as experimental paratenic hosts in studies by Poinar and Doelman (1974).

Parachordodes tegonotus Poinar, Rykken and Labonte (2004) has only been reported from Oregon. Developmental hosts are the ground beetles Pterostichus inopinus Casey, Pterostichus castaneus Dej. and Pterostichus amethystinus Mann. (Carabidae: Coleoptera) (Fig. 2-1). Paratenic hosts include mayfly larvae and larvae of the caddis fly, Rhyacophila sp. (Fig. 2-3). The latter is a predator and probably represents a secondary paratenic host, having ingested mayfly primary paratenic hosts.

Paragordius varius (Leidy 1851) occurs throughout North America (Chandler, 1985) including Hawaii (Camerano, 1901). Developmental hosts include the orthopterans, Gryllus sp., Gryllus assimilis (Fab.), Gryllus pennsylvanicus and Nemobius fasciatus (DeGreer) (Montgomery, 1903; Poinar and Weissman, 2004; Schmidt-Rhaesa et al., 2003; Ward and Whipple, 1918). White (1969) mentions larval mayflies (Baetes spp., Leptophlebia sp., Ephemerella spp.), caddis flies (Brachycentrus sp.), black flies (Simulium spp.) and corixids (Sigara sp.) as hosts for the larvae of P. varius. Unfortunately, it is not clear whether the hairworm larvae were developing or just encysted in these hosts. However, the like-lihood of hairworms developing in such small hosts as blackflies is negligible. It is possible that some of the infections, especially those in the blackflies, were caused by mermithid nematodes. Until further evidence to the contrary, these records are considered as representing paratenic hosts.

Pseudochordodes gordioides (Montgomery 1898a) has been reported from Western United States (Schmidt-Rhaesa et al., 2003).

Pseudochordodes manteri Carvalho 1942 has been reported only from Nebraska.

Pseduochordodes taxanus Schmidt-Rhaesa et al., 2003 was described from a cave in Texas, which is the only known locality.




BAIRD, W. 1853. Descriptions of some new species of Entozoa from the collection of the British Museum. Pro. Zool. Soc. London, 21:18-25.

BOLEK, M. G. AND J. R. COGGINS. 2001. Seasonal occurrence and observations on the life history of Gordius difficilis (Nematomorpha: Gordioidea) from Southeastern Wisconsin, USA. J. Parasitol., 88:287-294.

CAMERANO, L. 1892. Descrizione di una nuova specie di Gordius di Palmeira (Parna) raccolta dal dotter G. Franco Grillo. Ann. Mus. Civ. Di Genova, Ser. 2, 10:965-966.

_____. 1896. Gordiens nouveaux ou peu connus du musee zoologique de I' Academie Imperiale des Sciences de St. Petersbourg. Ann. Mus. Zool. Acad. Imp. St Petersbourg, 1:117-125.

_____. 1897. Monografia dei Gordii: Memoire delle Reale Accademia Science di Torino. 47:339-415.

_____. 1901. Gordii di Madgascar e delle isole Sandwich. Boll. Mus. Zool. Anat. Comp. Univ. Torino, 16: 1-2.

_____. 1915. Revisione dei Gordii. Mem. R. Accad. Sci. Torino, 66:1-66.

CAPPUCCI, D. T. 1977. The biology of Gordius robustus Leidy with a host list and summary of the public health importance of the Gordioidea. Dissertation Abstracts International, 37: 1-2.

CAPUSE, I. 1970. Nouvelles donnees sur la repartition et la biologie de quelques Gordiides de Roumanie. Trav. Mus. Hist. Nat. "Grigore Antipa", 10:49-56.

CARVALHO, J. C. M. 1942. Studies on some Gordiacea of North and South America. J. Parasitol., 28:213-222.

CHANDLER, C. M. 1985. Horsehair worms (Nematomorpha, Gordioidea) from Tennessee, with a review of taxonomy and distribution in the United States. J. Tennessee Acad. Sci., 60: 59-62.

DIESING, K. M. 1861. Revision der Nematoden: Sitzungsber. Akad. Wissensch. Wien, 42:599-605.

HANELT, B., AND J. JANOVY JR. 2000. New host and distribution record of Gordius difficilis (Nematomorpha: Gordioidea) from a vivid metallic ground beetle Chlaenius prasinus (Coleoptera: Carabidae) from western Nebraska, USA. Comparative Parasitol., 67:107-108.

HEINZE, K. 1934. Revision von Gordius flavus Linstow 1906 und Gordius flavus G. W. Muller 1927. Zool. Anzeig., 105:106-109.

LEIDY, J. 1851. Gordiaceae. Proc. Acad. Nat. Sci. Philadelphia, 5:262-263.

_____. 1856. A synopsis of Entozoa and some of their ectocongeners, observed by the author. Proc. Acad. Nat. Sci. Philadelphia, 8:42-58.

_____. 1870. The Gordius, or hair-worm: American Entomologist and Botanist, 2:193-197.

_____. 1871. Notice of some worms. Proc. Acad. Nat. Sic. Philadelphia, 23:305-307.

MAY, H. G. 1919. Contributions to the life history of Gordius robustus Leidy and Paragordius varius (Leidy). Illinois Biol. Monographs, 5:1-118.

MIRALLES, DE, D. A. B., AND L. C. VILLALOBOS, DE. 1995. A review of the Gordiacea (Nematomorpha) in the collection of the California Academy of Sciences with the description of a new species. Graellsia, 51:17-22.

MIRALLES, DE, D. A. B., VILLALOBOS, L. C. AND A. RODRIGUEZ. 1997. Una nueva especie y una nueva combinacion de gordiaceos (Nematomorpha). Neotropica, 43:53-56.

MONTGOMERY, JR. T. H. 1898a. The Gordiacea of certain American collections, with particular reference to the North American fauna. Bull. Mus. Comp. Zool., 32:21-59.

_____. 1898b. The Gordiacea of certain American collections, with particular reference to the North American fauna. Proc. California Acad. Sci., 1:333-342.

_____. 1903. The adult organization of Paragordius varius (Leidy). Zool. Jahrb. Anat. Ontog. Tiere, 18:387-474.

_____. 1907. The distribution of the North American Gordiacea, with description of a new species. Proc. Acad. Nat. Sci. Philadelphia, 59:270-272.

POINAR, JR., G. O. 2001. Nematoda and Nematomorpha. Pp. 255-295 in Ecology and classification of North American Freshwater Invertebrates, 2nd ed. (J. H. Thorp and A. P. Covich, eds.). Academic Press, San Diego.

POINAR, JR., G. O. AND D. B. WEISSMAN. 2004. Hairworm and nematode infections in North American Orthoptera. J. Orthoptera Res. (in press).

POINAR, JR., G. O., J. RYKKEN, AND J. LABONTE. 2004. Parachordodes tegonotus sp. n., (Gordioidea: Nematomorpha), a hairworm parasite of ground beetles (Carabidae: Coleoptera) with a summary of gordiid parasites from Carabidae. System. Parasit., 58:139-148.

POINAR, JR., G. O., AND C. DOELMAN. 1974. A re-examination of Neochordodes occidentalis (Mont.) comb. n. (Chordodidae: Gordioidea): larval penetration and defense reaction in Culex pipiens L. J. Parasitol., 60:327-335.

REDLICH, A. 1980. Description of Gordius attoni sp. n. (Nematomorpha, Gordiidae) from northern Canada. Can. J. Zool., 58:382-385.

ROMER, F. 1897. Gordiiden. Abh. Senckenb. Naturf. Ges., 23: 247-295.

ROSA, D. 1881. Nota intorno al Gordius villoti n. sp. ed al G. tolosanus Duj. Atti R. Accad. Sci. Torino, 16:333-341.

SCHMIDT-RHAESA, A. 1997. Nematomorpha. In: Susswasserfauna von Mitteleuropa, Vol. 4(4) (J. Schwoerbel and P. Zwick, eds.). Gustav Fisher Verlag, Stuttgart.

SCHMIDT-RHAESA, A., B. HANELT. AND W. K. REEVES. 2003. Redescription and compilation of Nearctic freshwater Nematomorpha (Gordiida), with the description of two new species. Proc. Acad. Nat. Sci. Philadelphia, 153:77-117.

SMITH, D. G. 1991. Observations on the morphology and taxonomy of two Parachordodes species (Nematomorpha, Gordioida, Chordodidae) in southern New England (USA). J. Zool. (London), 225:469-480.

_____. 1994. A reevaluation of Gordius aquaticus difficilis Montgomery 1898 (Nematomorpha, Gordioidea, Gordiidae). Proc. Acad. Nat. Sci., Philadelphia, 145:29-34.

_____. 2001. Pennak's Freshwater Invertebrates of the United States, 4th ed. Porifera to Crustacea. John Wiley and Sons, Inc. New York.

STUDIER, E. H., K. H. LAVOIE, AND C. M. CHANDLER. 1991. Biology of cave crickets, Hadenoecus subterraneus, and camel crickets, Ceuthophilus stygius (Insecta: Orthoptera): Parasitism by hairworms (Nematomorpha). J. Helminthol. Soc. Washington, 58:248-250.

THORNE, G. 1940. The hairworm, Gordius robustus Leidy, as a parasite of the Mormon cricket, Anabrus simplex Haldeman. J. Washington Acad. Sci., 30:219-231.

WARD, H. B., AND G. C. WHIPPLE. 1918. Fresh-Water Biology. John Wiley and Sons, Inc. New York.

WHITE, D. A. 1969. The infection of immature aquatic insects by larval Paragordius (Nematomorpha). Great Basin Naturalist, 29:44.


Department of Zoology, Oregon State University, Corvallis, OR 97331

Professor Emeritus, Biology, Middle Tennessee State University, 1016 W. Cunningham St., Milan, TN 38358
TABLE 1. Species of hairworms (with synonyms) reported from North

Species                                  Synonym

Chordodes morgani Montgomery 1898a       C. puerilis Montgomery 1898a
Gordionus densareolatus (Montgomery      Parachordodes densareolatus
  1898a) nov. comb                         (Montgomery 1898a) (Camerano,
                                           1915) (Schmidt-Rhaesa et al.,
                                         Gordius densareolatus
                                           Montgomery 1898a
                                         G. leidyi Montgomery 1898a
Gordionus lineatus (Leidy 1851)          Parachordodes lineatus (Leidy
  (Schmidt-Rhaesa et al., 2003)            1851) (Camerano, 1915)
                                         Gordius lineatus Leidy 1851
Gordionus longareolatus (Montgomery      Parachordodes longareolatus
  1898b) (Schmidt-Rhaesa et al., 2003)     (Montgomery 1898b) (Camerano,
                                         Gordius longareolatus
                                           Montgomery 1898b
Gordionus platycephalus (Montgomery      Parachordodes platycephalus
  1898a) (Schmidt-Rhaesa et al., 2003)     (Montgomery 1898a) (Camerano,
                                         Gordius platycephalus
                                           Montgomery 1898a
Gordionus sinepilosus Schmidt-Rhaesa et
  al. 2003
Gordionus violaceus (Baird 1853)         Parachordodes violaceus (Baird
  (Heinze, 1935)                           1853) (Camerano, 1897)
                                         Gordius violaceus Baird 1853
Gordius alascensis Montgomery 1907       Gordionus alascensis
                                           (Montgomery 1907) (Schmidt-
                                           Rhaesa et al., 2003)
                                         Parachordodes alascensis
                                           (Montgomery 1907) (Chandler,
Gordius attoni Redlich 1980
Gordius difficilis Montgomery 1898a,     Gordius aquaticus difficilis
  (Smith, 1994)                            Montgomery 1898a
Gordius robustus Leidy 1851              Gordius aquaticus robustus
                                           Montgomery 1898a
                                         G. agassizi Montgomery 1898a
                                         G. lacustris Leidy 1871
                                         G. subspiralis Diesing 1861
                                         G. californicus Camerano 1915
                                         G. villoti Rosa 1881
                                           (Montgomery, 1907)
                                         G. fasciatus Baird 1853
                                         G. hawaiiensis Heinze 1934
Neochordodes californensis de Miralles
  & de Villalobos 1995
Neochordodes occidentalis (Montgomery    Chordodes occidentalis
  1898a)                                   Montgomery 1898a
Parachordodes tegonotus Poinar et al.
Paragordius varius (Leidy 1851)          Gordius varius Leidy 1851
  (Camerano, 1897)                       G. longilobatus Leidy 1870
                                         Chordodes varius Romer 1897
Pseudochordodes gordioides (Mongomery    Chordodes gordioides Montgomery
  1898a) (de Miralles et al., 1997)        1898a
                                         Pseudochordodes bedriagae
                                           (Camerano 1896) (Schmidt-
                                           Rhaesa et al., 2003)
Pseudochordodes manteri Carvalho 1942
Pseudochordodes texanus Schmidt-Rhaesa
  et al. 2003.


A Cuticle smooth, lacking areoles or     B
  with flat, smooth areoles; male
  tail bilobed (as in Figs. 1-1, 2,
  3), with a postcloacal or
  precloacal ridge or crescent;
  female tail entire--Gordiidae
  May 1919--Gordius L.
A Cuticle with distinct areoles usually  E
  ornamented with bristles or
  tubercles; male tail entire (Fig.
  1-5) or if bilobed, then without a
  postcloacal (Fig. 1-1) or precloacal
  ridge or crescent (as in Fig. 1-3);
  female tail entire or trilobed (Fig.
B Male cuticle with large white spots;   Gordius attoni Redlich 1980
  broad semicircular postcloacal
  crescent present (Fig. 1-1); elongate
  white triangular streak from neck to
  anterior fourth of body in both
  sexes; head tapers (spindle-shape)
B Male cuticle with or without white     C
  spots, lacking an elongate white
  triangular streak; head variable
C Male with both a precloacal            Gordius difficilis Montgomery
  semicircular hairline and a            1898a, (Smith 1994)
  postcloacal ridge (Fig. 1-2); areoles
  present or absent on females
C Male with either a postcloacal or a    D
  precloacal ridge, but not both
D Male with a precloacal ridge (Fig.     Gordius alascensis Montgomery
  1-3) areoles confluent,                1907
D Male with a postcloacal ridge (Fig.    Gordius robustus Leidy 1851
  1-1); areoles absent
E Female tail trilobed (Fig. 2-2); male  Paragordius varius (Leidy 1851)
  tail bilobed with length of lobes
  greater than twice their width (Fig.
  1-4); head end obliquely truncated
E Female tail entire; male tail bilobed  F
  with length of lobes equal to or less
  than twice their width (as in Fig.
  1-1, 2, 3), or male tail entire (Fig.
F Male tail bilobed                      M
F Male tail entire, lobes absent or      G
G Cuticle with normally one kind of      H
  areole--Neochordodes Carvalho 1942
G Cuticle with two or more types of      J
H Areoles containing short bristles and  Neochordodes occidentalis
  tubercles (some specimens possess a    (Montgomery 1898a,b)
  smaller type of areole)                (Poinar and Doelman 1974)
H Areoles lacking bristles or tubercles  Neochordodes californensis
                                         de Miralles and de Villalobos
J Areoles with prominent tubercles,      Chordodes morgani (Montgomery
  crowns or papillae; female cloacal     1898a)
  aperture terminal
J Areoles without prominent tubercles,   K
  crowns or papillae; female cloacal
  aperture subterminal--Pseudochordodes
  Carvalho 1942
K Smaller areoles with knobs on          Pseudochordodes gordioides
  surface; arranged randomly             (Montgomery 1898a)
K Smaller areoles without knobs on       L
  surface, arranged in uneven rows
L Large elevated areoles in clusters of  Pseudochordodes manteri
  usually two                            Carvalho 1942
L Large elevated areoles in clusters of  Pseudochordodes taxanus
  three and four                         Schmidt-Rhaesa et al. 2003
M Areoles of two types, large            Parachordodes tegonotus Poinar,
  megareoles with a central pore or      Rykken and LaBonte 2004
  tubercle and small microareoles
  lacking a pore or tubercle; broad
  hair line of short simple and
  branched hairs beginning anterior to
  cloacal aperture but not reaching to
  point of bifurcation of tail lobes
  (Fig. 1-8)
M Areoles of one (microareolar) type,    N
  lacking a central pore or tubercle--
  Gordionus Muller
N Oblique rows of single and/or          O
  branched hairs flanking cloacal
  aperture (Fig. 1-6, 7); areoles
  closely opposed, may produce
  longitudinal ridges
N No such hairs on lateral body surface  P
  flanking cloacal aperture
O Body dark brown; areoles irregularly   Gordionus violaceus (Baird
  polygonal, not arranged in rows, well  1853)
  separated from one another by
  distinct interareolar region;
  interareolar spaces with small
  spinules or papillate processes;
  areoles not showing sexual
  dimorphism; hairline on male tail not
  reaching point of bifurcation of tail
  lobes (Fig. 1-6); calotte white
O Body light yellow to deep buff;        Gordionus lineatus (Leidy 1851)
  areoles closely opposed without
  intervening spaces, having a tendency
  to group themselves in longitudinal
  rows in males (sexual dimorphism);
  hairline extending beyond point of
  bifureation of tail lobes (Fig. 1-7);
  calotte dark or absent
P Tubercles located behind male cloacal  Q
  aperture (Fig. 1-7, 8); tale lobes of
  male shorter than, equal to or longer
  than wide; female tail not swollen;
  head variable
P No tubercles behind male cloacal       Gordionus platycephalus
  aperture (Fig. 1-9); tail lobes of     (Montgomery 1898a)
  male longer than wide; female tail
  swollen; head flattened
Q Tail lobes of males short (Fig.        Gordionus densareolatus
  1-10), length equal to or shorter      (Montgomery 1898a)
  than width; black ring surrounds
  cloacal aperture; postcloacal
  integumentary ridge; tubercles extend
  anterior to cloacal aperture; areoles
  more or less confluent, tending to
  merge with one another and produce
  transverse rows, head usually
Q Tail lobes of males longer than wide   R
  (Fig. 1-11); no black ring around
  cloacal aperture, postcloacal
  integumentary ridge absent; tubercles
  not extending anterior to cloacal
R Areoles elongated, well separated      Gordionus longareolatus
  from one another: few interareolar     (Montgomery 1898b)
  structures (tubercles)
R Areoles rounded to polygonal,          Gordionus sinepilosus Schmidt-
  numerous bristles in interareolar      Rhaesa et al. 2003
Gale Copyright:
Copyright 2004 Gale, Cengage Learning. All rights reserved.