Arachnids of North Carolina
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View Sclerosomatidae Members: NC Records

Leiobunum formosum Wood, 1870 - No Common Name

Leiobunum formosumLeiobunum formosumLeiobunum formosum
Taxonomy
Order: OPILIONESSuborder: EupnoiSuperfamily: PhalangioideaFamily: Sclerosomatidae                                                                                 
Comments: Approximately 30 species in this genus have been identified as occurring in North America north of Mexico (Cokendolpher and Lee, 1993; Ingianni et al., 2011), with 16 recorded in North Carolina. However, the validity of several of these species is suspect, with several that will probably be determined to be synonyms of other species, e.g., davisi, speciosum, and zimmermani in North Carolina Burns et al., 2012; Shultz, 2018). According to Shultz (2018), moreover, recent phylogenetic studies indicate both that more species are waiting to be described and that the name Leiobunum may eventually be restricted to European species, requiring new generic names for most, if not all, of our species.
Species Comment: This species will likely be moved from Leiobunum to Hadrobunus based on genetic analysis (Burns et. al., 2012; Shultz, 2012)
Identification
Online Description/Photos: BugGuide Google, iNaturalist, Wikipedia, GBIFTechnical Description: Davis (1934); Shultz (2018)
Comments: Large harvestmen, especially the females; approximately the same size as Hadrobunus maculosus. Males are uniform orange-yellow or red-brown above, with a dark optical tubercle; the central figure is well marked in early season individuals but becoming obscure with age, with only traces of the outline present on the anterior of the scutum (Davis, 1934; Shultz, 2018). The venter is only slightly lighter than the dorsum. Females are darker brown with again a well-developed central figure in early season individuals but more obscure in older ones; transverse rows of light spots are present on the abdomen (Shultz, 2018); in our specimens, there is a light band towards the rear of the abdomen. The palps are yellow marked with brown. The trochanters of the legs are dark and strongly contrasting with the pale coxae; the remainder of the legs are yellowish but with dark annulations at the joints. Similar in appearance to L. verrucosum, although that species lacks the dark annulations on the legs.
Total Length: ~6 mm, males; 9–10 mm, females (Shultz, 2018)Adult ID: identifiable by photo of specific features and/or supplementary info
Structural Features: The femur of the foreleg is longer than the body, unlike most Hadrobunus species. Male and female reproductive structures are diagnostic (see Davis, 1934; Shultz, 2018).
Structural photos
Leiobunum formosum
Apex of genital operculum, interior side. A small sclerotized lobe, as illustrated by Shultz (2018) is not clearly defined but there is a thin flange that appears to extend down from the apex. Female collected by Steve Hall and David George, Chatham County, 2024-07-28		 Leiobunum formosum
Small conical process at the retrolateral sided of second coxa, next to junction with the trochanter. Female collected by Steve Hall and David George, Chatham County, 2024-07-28
Distribution in North Carolina
Comments: So far recorded in North Carolina only from the Piedmont
County Map: Clicking on a county returns the records for the species in that county.
Leiobunum formosum
Adult phenology:
 High Mountains (HM) ≥ 4,000 ft.
 Low Mountains (LM) < 4,000 ft.
 Piedmont (Pd)
 Coastal Plain (CP)

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