Spiders of North Carolina

Order:
Scientific Name: Common Name:		Family (Alpha):

View	Sclerosomatidae Members:	NC Records
Leiobunum formosum Wood, 1870 - No Common Name

Taxonomy

Order: OPILIONES	Suborder: Eupnoi	Superfamily: Phalangioidea	Family: 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, GBIF

Technical 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

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

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.


Adult phenology: High Mountains (HM) ≥ 4,000 ft. Low Mountains (LM) < 4,000 ft. Piedmont (Pd) Coastal Plain (CP) Click on graph to enlarge

Habitats and Life History

Habitats: In Tennessee, formosum is commonly encountered in stands of pine and mixed hardwoods (Townsend et al., 2006)
Observation Methods:
Abundance/Frequency: We currently have too few records from North Carolina to judge its frequency of occurrence or abundance
Behavior: In Tennessee, adults overwinter and late spring and early summer populations frequently consist of both juveniles and adults (Townsend et al., 2006)

Status in North Carolina

Natural Heritage Program Status:

Natural Heritage Program Ranks: [GNR] [SU]

State Protection: Arachnids are not protected under state law, although permits are needed to collect them in State Parks and other public and private nature preserves

Comments: We have only a single relatively old (1976) record for this species. While this species does not appear to be habitat limited, we need much more information on its distribution in the state, its habitat preferences, and population trends before we can begin to estimate its conservation status.

Photo Gallery for Leiobunum formosum - No common name		Photos: 11
	Recorded by: David George and Steve Hall on 2024-08-31 Chatham Co. Comment:	Recorded by: Steve Hall, David George, Pat Coin, Jeff Niznik, Carol Tingley, and Tom Howard on 2024-07-28 Chatham Co. Comment: Adult female
	Recorded by: Steve Hall, David George, Pat Coin, Jeff Niznik, Carol Tingley, and Tom Howard on 2024-07-28 Chatham Co. Comment:	Recorded by: Steve Hall, David George, Pat Coin, Jeff Niznik, Carol Tingley, and Tom Howard on 2024-07-28 Chatham Co. Comment:
	Recorded by: Steve Hall, David George, Pat Coin, Jeff Niznik, Carol Tingley, and Tom Howard on 2024-07-28 Chatham Co. Comment: Adult male	Recorded by: Owen McConnell on 2020-10-07 Orange Co. Comment:
	Recorded by: Steve Hall on 2020-06-30 Orange Co. Comment: Immature	Recorded by: Steve Hall on 2020-06-30 Orange Co. Comment:
	Recorded by: Steve Hall on 2019-06-24 Orange Co. Comment: Immature	Recorded by: Steve Hall on 2019-06-24 Orange Co. Comment:
	Recorded by: Steve Hall on 2019-06-24 Orange Co. Comment:

Leiobunum formosum Wood, 1870 - No Common Name

Photo Gallery for Leiobunum formosum - No common name

Photos: 11