Speodesmus aquiliensis Shear, 1984.

Distinct from the similar Pratherodesmus Shear, 2009 in its much larger gonopod solenomere and endomerite, from Tidesmus Chamberlin, 1943, Sequoiadesmus Shear & Shelley, 2008 and Nevadesmus Shear, 2009 in having a simple, unbranched endomerite, or endomerite lacking. Packardesmus Shear & Shelley, 2019 has all gonopod branches clustered at the tip of an extended prefemoral stem.

Small, probably troglobiotic macrosternodesmines 4.0–11.0 mm long, lacking pigment. Nineteen trunk rings (collum + 17 pedigerous rings + telson). Head sparsely to densely setose. Antennae (Fig. 22) relatively short, elbowed between antennomeres three and four, antennomere six much enlarged, with subapical accessory sensory organ. Order of length of antennomeres: 6>3=4>5>2>7>1>8. Collum with three rows of eight setae (number may vary on more posterior rings); anterior row at anterior margin of collum, middle row may be dispersed, posterior row at posterior margin of collum. Collum setae on low tubercles or sockets more or less flush with surface. Subsequent rings with anterior row posterior to anterior margin of metazonite, but posterior row at posterior edge of metazonite, rows of 6–10 setae or setae becoming more scattered on more posterior rings. Metazonites with narrow paranota bearing three short, marginal teeth corresponding to setal rows, posteriolateral metazonite corners acute to projecting. Limbus minutely dentate. Ozopores laterodorsal, at posteriolateral corners, opening in a distinct pore callus. Pore formula 5, 7, 9, 10, 12, 13, 15–18. Penultimate ring with 10–18 scattered setae, telson with 8–10 scattered setae, epiproct process short, blunt, with four spinnerets set in shallow depression. Paraprocts and hypoproct with two setae. Dorsal setae post-collum on more prominent tubercles, setae themselves may be long, acute, or short, clavate. Males with all legs having dorsally swollen prefemora, femora also dorsally swollen, curved, both podomeres ventrally with many sphaeotrichomes; postfemora and tibiae normal, with few ventral sphaerotrichomes or sphaerotrichomes absent (Fig. 4). Gonopod socket rounded-cordate, often with anterior rim, midposterior portion extending slightly between ninth coxae. Gonopods joined by tough membrane anteriorly; small, more sclerotized strip represents sternal remnant, articulates mesally with coxae. Gonopod coxae not movable, tightly appressed in midline but not fused, anteriomesally excavate to receive telopodite. Telopodites movable only in plane parallel to body axis. Prefemorites transverse across posterior surface of coxae. Prefemoral process single, broad, prefemoral process and acropodite on short stem arising from prefemorite. Acropodite with long seminiferous branch, pore surrounded by minute cuticular extensions, these sometimes extending distad along concave mesal surface of distal zone. Distal zone long, tapering, acute, or short, blunt. Endomerite arising basally or midway on acropodite.

From the state of Colorado, to which the genus appears endemic, and the common combining stem -desmus in the order.

In addition to the type species, the following new species: beckleyi, warneri, hopkinsae and manitou.

See Map 1. Caves in central and northern Colorado, USA. Species distributions appear to be defined by major rivers and large canyons. Groaning Cave where C. hopkinsae occurs is across Deep Creek Canyon from La Sunder Cave where C. beckleyi occurs and this canyon is 2,000’ deep. The Colorado River may define the limits of C. aquiliensis relative to C. beckleyi and C. hopkinsae because C. aquiliensis has only been collected south of the Colorado River, while the other two species were collected north of the river. It is likely that Coloradesmus will extend into Wyoming because C. warneri was collected 5 miles from the state line.

Map 1. 

Northwestern Colorado, showing the distribution of Coloradesmus species. Green area indicates Colorado Rocky Mountain Forest Ecoregion. Symbols may represent more than one locality as some caves are very close to one another. Stars, C. aquilensis, triangles, C. hopkinsae, squares, C. manitou, circles, C. buckleyi, hexagon, C. warneri.

Two species groups are recognizable in this genus, distinguished primarily by size and the presence or absence of a distinct endomerite. Coloradesmus aquiliensis, C. hopkinsae and C. manitou are 0.6 mm or greater in width and from 5–11 mm long, depending on the contraction or extension of the body. Coloradesmus beckleyi and C. warneri are considerably smaller, about 0.4 mm wide and 4 mm long, placing them among the smallest of all millipedes. The former three species have distinct endomerites, while endomerites seem lacking in the latter two. Division of Coloradesmus may prove desirable in the future but for now we prefer to group all the species in a single genus.

All specimens of Coloradesmus were collected in the dark zones of limestone caves. The preferred habitat for the genus appears to be caves with moist organic materials including wood, scat and guano. Millipedes representing Coloradesmus were found under rocks, burrowing in cave soils, and on wet cave formations. Many of the caves where Coloradesmus occurs are remote and at high-altitudes with temperatures of 2–4 °C.

Establishing troglobiosis is difficult in macrosternodesmines due to the small size and depigmented appearance of nearly all species except those of Tidesmus. Eyelessness is not a marker of troglobiotic adaptation in Polydesmida, since all known species of the order, some thousands, are eyeless. However, despite antennae and legs that seem not much elongated compared to those of litter-dwelling species of Chaetaspis, the species of Coloradesmus have a loose-jointed, elongated appearance as a whole that, along with the weak sclerotization of the rings, suggests a significant degree of adaptation.

As WAS has repeatedly emphasized in previous publications, collecting in caves has generally been more intense than surface collecting, especially in western parts of the United States. Further, suspect troglobionts tend to be very small and would only be found outside caves by very careful sifting of forest litter at an appropriate season of the year, if they exist there. Many caves in the Rocky Mountains are at high altitudes or are situated in surroundings that would not be very conducive to the survival of small, delicate arthropods on the surface. The mesovoid space of small cavities from a few centimeters to meters underground has not been explored by collectors in western North America.

Male holotype (American Museum of Natural History) from Fulford Cave, 21 mi SE of Eagle, Eagle Co.: Colorado, collected 6 July 1980 by J. R. Holsinger et al.

A larger species of Coloradesmus distinguished by details of the gonopods; in Coloradesmus hopkinsae the prefemoral process is much broader and has a laterodistal tooth. Coloradesmus manitou differs from C. aquiliensis in the endomerite, which in manitou emerges from the acropodite at nearly a right angle, then turns sharply distad. Coloradesmus beckleyi and C. warneri are only half the length of the other three known species of the genus.

With the characters of the genus. Lengths of a series of specimens from Fulford Cave, the type locality, varied from 4.5–6.2 mm, the longer specimens strongly extended. Setae on collum, metazonites and telson long, acute. In the description of the gonopods, the prefemoral process is erroneously described as bifid and the endomerite is shown in the drawings as attached to the prefemoral process, giving that impression.

Figures 1–6. 

Coloradesmus aquiliensis male. 1 Collum, dorsal view 2 midbody ring, dorsal view 3 telson, dorsal view 4 right leg 7, posterior view 5 gonopods, ventral view 6 gonopods, posterior view. See text for explanation of labels.

Figures 7–10. 

Coloradesmus species males. 7 C. aquiliensis gonopods, anterior view 8 C. aquiliensis gonopods, lateral view 9 C. hopkinae collum, dorsal view 10 C. hopkinae midbody ring, dorsal view. See text for explanation of labels.

COLORADO: Eagle Co.: Fulford Cave, 10,000’ asl, organic matter in packrat midden, 39°29'N, 106°33'W, 22 June 1999, 7 males, 13 females (topotypes); Devil’s Den Cave, 11,500’ (3506 m) asl, 35°F, under stones and logs in dark zone, 39°30'N, 106°37'W, 25 August 1999, 18 males, 7 females, juveniles; Herbie’s Deli Cave, 9200’ asl, under rocks in dark zone, 40°01'N, 105°40'W, 31 August 2003, mf; 15 August 2007, 2 males; Lime Creek Cave, 9200’ (2804 m) asl, 40°00'N, 105°40'W, 5 September 2001, 2 males.

Male holotype and male paratypes from Colorado, Garfield Co.: Bair Cave, 9800’ asl, 39°38'N, 107°14'W, 200 ft from entrance, collected September 1998 and 19 June 1999 by D. Steinmann.

Similar in somatic characters to both C. aquiliensis and C. manitou, but differing from both in the broader, more irregularly shaped prefemoral process of the gonopods, and in having a short endomerite tightly appressed to the prefemoral process.

The species is named in honor of Kay Hopkins of the United States Forest Service for her contributions to cave conservation, cave research and cave preservation.

Male holotype. Length about 7.0 mm, greatest width 0.66 mm. With the characters of the genus. Head sparsely setose. Basal joint of mandibles not greatly exceeding width of collum; front margin of collum evenly arcuate, posterior margin shallowly embayed (Fig. 9). Setae of collum and metazonites acute throughout (Figs 9–11), setal rows of metazonites sometimes interrupted, supplemental setae sometimes present (Fig. 10). Setal tubercles become more prominent posteriorly (cf. Figs 10, 11). Telson rounded, with two distinct rows of setae; epiproct blunt (Fig. 11). Gonopod socket occupies entire width of prozonite, subcordate, indenting ninth sternite (Fig. 12). Gonopods with robust acropodite (a, Fig. 13), ending in long, acute distal zone (dz, Figs 13, 14); seminal pore long, with many tiny finger-like cuticular projections (Fig. 15); endomerite (e, Fig. 13) short, tightly appressed to prefemoral process. Prefemoral process (pfp, Figs 13, 14), large, broad, scoop-shaped, with subapical lateral tooth, tip acute, slightly lobed.

Figures 11–14. 

Coloradesmus hopkinae male. 11 Telson, dorsal view 12 gonopods, ventral view 13 right gonopod, mesal view 14 right gonopod, medioposterior view. See text for explanation of labels.

Figures 15–20. 

Coloradesmus species males. 15 C. hopkinae, gonopod seminal pore 16–20 C. manitou 16 collum, dorsal view 17 midbody ring, dorsal view 18 telson, dorsal view 19 gonopods, ventral view 20 Gonopods, posterior view. See text for explanation of labels.

COLORADO: Garfield Co.: Groaning Cave, 39°42'N, 107°10'W, 9800’ (2804 m) asl, 9 October 2008, D. Steinmann, male, females, juveniles.

Male holotype and many male and female paratypes from Manitou Cave, El Paso Co.: Colorado, 7000’ asl, collected 3 August 1996, by D. Hubbard.

A larger species, like C. aquiliensis and C. hopkinsae, but differing in that the metazonital setal tubercles are very low and often scattered across the metazonite, not in rows. The gonopod endomerite is stouter than in C. aquiliensis and emerges from the acropodite at almost a right angle, then turning distad; the distal zone is shorter and often curved. Unlike C. hopkinae, the gonopod pore is compact with few cuticular projections.

The species epithet is a noun in apposition, after the type locality.

Male paratype. Length 8.0–10.5 mm, depending on degree of extension, greatest width 0.9 mm. With the characters of the genus. Head densely setose, basal joint of mandibles slightly exceeding width of collum (Fig. 16). Collum with three rows of long, acute setae (Fig. 16). Midbody metazonites nearly smooth, setal tubercles low to absent; setae becoming shorter posteriorly (Fig. 17), rows disrupted so that setae may appear scattered. Telson with 12–15 long, acute, scattered setae, rounded, epiproct hardly distinct. Gonopod socket occupying entire width of prozonite, nearly circular with strong projecting anterior margin, not indenting sternite nine (Fig. 19). Gonopods with subhemispherical coxae (cx, Fig. 19) immovable, completely filling socket; acropodite arises on distinct stem (s, Fig. 19); prefemoral process relatively narrow, margins even, not scoop-like (pfp, Figs 20, 21); acropodite (a, Figs 20, 21) robust, distal zone (dz, Fig. 21) short, strongly curved; endomerite (e, Figs 20, 21) nearly as large, robust as acropodite, at wide angle to acropodite.

Figures 21–25. 

Coloradesmus species males. 21 C. manitou gonopods, posterior view 22–24 C. lasunda male 22 head, collum and anterior four rings, dorsal view 23 collum, dorsal view 24 midbody ring, dorsal view 25 telson, dorsal view. See text for explanation of labels.

Female paratype. Closely similar to male in all nonsexual characters.

COLORADO: Fremont Co.: Fly Cave, 7 August 1996, D. Hubbard, 2 males; Marble Cave, 7 August 1996, D. Hubbard, 7 males and 8 females (these two caves are nearly adjacent at 38°36'N, 105°13'6.500"W (1982 m) asl; El Paso Co.: Cave of the Winds, 7000’ (2134 m) asl, 38°55'N, 104°55'W, 2 August 1996, D. Hubbard, 10 males, 6 females and 20 February 2007, David Steinmann, 6 males, 6 females; Dilation Cave, 7400’ (2256 m) asl, 38°48'N, 104°52'W, 19 June 2009, D. Steinmann, male; Pedro’s Cave, 6800’ (2073 m) asl, 38°55'N, 104°55'W, 5 January 2008, D. Steinmann, male, females, juveniles.

Male holotype and male and female paratypes from La Sunder Cave, Garfield Co.: Colorado, 7500’ (2287 m) asl, 39°42'N, 107°10'W, in organic matter and under cardboard along the first 1000’ of passage, collected 31 July 1999 by D. Steinmann.

A small species of Coloradesmus, as is the following species, but differing from C. warneri in details of the gonopods, as shown in Figs 28–29.

The species epithet honors Steve Beckley, for his dedication to cave conservation and education as the owner of Glenwood Caverns in nearby Glenwood Springs.

Male holotype. Length, about 4 mm, greatest width 0.4 mm. Head with short, sparse setae; basal joint of mandible exceeding width of collum (Fig. 22). Collum relatively short, posterior margin evenly, concavely curved (Fig. 23); collum setae short, clavate. Metazonites with somewhat suppressed but distinct paranota bearing obsolete teeth (Figs 22–25); setae distinctly clavate, short, set on prominent tubercles, rows even, uninterrupted. Telson (Fig. 25) with few setae, epiproct indistinct. Gonopods (Figs 26–28) with coxae rather oval, immovable; acropodite (a, Figs 26–28) robust, blocky, pore without cuticular fimbriae, endomerite evidently absent. Prefemoral process (pfp, Figs 26–28) exceeding acropodite, narrow, with distinct acute hook at tip.

Figures 26, 27. 

Coloradesmus lasunda male. 26 Right gonopod, mesal view 27 right gonopod, lateral view. See text for explanation of labels.

Figures 28, 29. 

Coloradesmus species gonopods, posterior views. 28 C. lasunda 29 C. warneri. See text for explanation of labels.

Female paratype. Similar in all nonsexual characters to male.

Known only from the type locality.

Male holotype and female paratype from White Water Cave, 6100’ (1860 m) asl, 40°54'N, 105°09'W, Larimer Co.: Colorado, collected 1 June 2007 by D. Steinmann.

Very similar in nonsexual characters to the foregoing species, but differing in details of the gonopods. Compare Figs 28, 29.

The species epithet honors Ed Warner, an active conservationist and donor to the Denver Museum of Nature & Science, for his dedication to nature and the environment.

In size and in nonsexual characters, this species is nearly identical to Coloradesmus beckleyi. Gonopods (Fig. 29) with large subhemispherical coxae immovable in gonopod socket. Acropodite (a, Fig. 29) long, relatively slender, not blocky, slightly curved. Pore lacking cuticular filaments. Distal zone (dz, Fig. 29) curved laterad, tapering, not bent at an angle; prefemora process (pfp, Fig. 29) slender, tapering, gradually curved.

Female paratype : Similar in all nonsexual characters to male.

COLORADO: Larimer Co.: White Water Cave, 3 November 2006, D. Steinmann, juveniles; Kremer’s Cave, 40°45'N, 105°10'W, 5600’ (1707 m) asl, dark zone, 12 August 2006, D. Steinmann, male; 29 March 2008, D. Steinmann, juveniles; Signature Cave, 40°75'N, 105°11'W, 6100’(1860 m) asl, 22 February 2011, D. Steinmann, male, juveniles; 22 October 2011, D. Steinmann, male, female, juveniles.

Females of a species of the European genus Polydesmus were collected along with the types in Whitewater Cave. All species of Polydesmus recorded from North America are anthropochoric.