Caerostris extrusa Butler 1882
Creators: name: Gregorič, Matjaž
name: Yu, Kuang-Ping
name: Velez, Winny Rojas
name: Garb, Jessica E.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Araneidae
Caerostris
Caerostris extrusa

description: Caerostris extrusa Butler, 1882
Figs 1D, 4, 6A–C; Appendix 1
Caerostris extrusa Butler, 1882: 100 (♀), plate 6 fig. 3.
Caerostris extrusa – Grasshoff 1984: 752 (♀), figs 28–30.
Diagnosis
As in C. kuntneri (Figs 6I, 7E), C. darwini (Kuntner & Agnarsson 2010: 6 e), C. mitralis (Grasshoff 1984: figs 19–20, 29–30), C. tinamaze (Gregorič et al. 2015b: fig. 9c), and C. wallacei (Gregorič et al. 2015b: fig. 10c), and in contrast to other Afrotropical species of Caerostris, the epigynal hooks in C. extrusa (Figs 4E, 6C) are short rather than long, positioned medially on the epigynal plate rather than anteriorly and pointing laterally rather than posteriorly. Different to all other species and as in C. darwini, the epigynal hooks in C. extrusa have an anteriorly pointing base that is longer than the hook length, but the hooks are wide and heavily sclerotized in C. extrusa but shorter and narrower in C. darwini. Male C. extrusa (Fig. 4K–M) differ from those of other Afrotropical Caerostris, except C. tinamaze (Gregorič et al. 2015b: fig. 9j–k), by the relatively small palpal bulbus, and from all Caerostris by the twisted conductor positioned at a perpendicular axis to the cymbium.
Type material
Holotype
MADAGASCAR • ♀; specimen photographs examined; BMNH, BMNH1882.26.
Other material examined
MADAGASCAR • 1 ♀; Toamasina Province, Mantadia National Park; lat. -18.783784, lon. 48.427617; 26. Feb. 2010; M. Kuntner, I. Agnarsson and M. Gregorič leg.; Cox1 not obtained; USNM, ARA4270 • 1♂; Toamasina Province, Analamazoatra National Park; lat. -18.937172, lon. 48.4200538; Dec.2017; M. Gregorič, M. Kuntner, I. Agnarsson and P. Babb leg.; GenBank accession number PP403861; ARA1965; USNM • 1 ♀; Antsiranana Province, Marojejy National Park; lat. -14.437629, lon. 49.775602, 30. Mar. 2022; M. Gregorič, M. Kuntner, K.P. Yu and M. Bedjanič leg.; GenBank accession number PP403853; ARA7936; ZRC SAZU • 1 ♀; Toamasina Province, Andasibe-Mantadia National Park; lat. -18.8255 lon. 48.4349; 6. Dec. 2017; M. Gregorič, M. Kuntner, I. Agnarsson and P. Babb leg.; GenBank accession number PP403854; CA2017067; ZRC SAZU • 1 ♀; Toamasina Province, Analamazoatra National Park; lat. -18.937172 lon. 48.420053; 10–16. Dec. 2017; M. Gregorič, M. Kuntner, I. Agnarsson and P. Babb leg.; GenBank accession number PP403855; CA2017089; ZRC SAZU • 1 ♀; same locality, date, and leg. data as for preceding; GenBank accession number PP403856; CA2017157; ZRC SAZU • same locality, date, and leg. data as for preceding; GenBank accession number PP403857; CA2017207; ZRC SAZU • 1 ♀; same locality, date, and leg. data as for preceding; GenBank accession number PP403858; CA2017221; ZRC SAZU • 1 ♀; same locality, date, and leg. data as for preceding; GenBank accession number PP403859; CA2017335; ZRC SAZU • 1 ♀; same locality, date, and leg. data as for preceding; GenBank accession number PP403860; CA2017379; ZRC SAZU • 1 ♂; same locality, and leg. data as for preceding; 9. Dec. 2017; GenBank accession number PP403862; ARA1974; ZRC SAZU • 1 ♂; Toamasina Province, Analamazoatra National Park; lat: -18.932779, lon. 48.413215; 7; Dec. 2017; M. Gregorič, I. Agnarsson, M. Kuntner and P. Babb leg.; GenBank accession number PP403863; ARA1981; ZRC SAZU • 1 ♀; Toamasina Province, Analamazoatra National Park; lat. -18.786784, lon. 48.427617; 26. Feb. 2010; M. Gregorič, I. Agnarsson and M. Kuntner leg.; Cox1 not obtained; ARA5603; ZRC SAZU.
Description
Female (ARA4270 from Andasibe-Mantadia National Park, Madagascar, Fig. 4A–E) MEASUREMENTS AND COLORATION. Total body length 20.11. Prosoma 7.84 long, 8.54 wide, 4.06 high. Carapace and chelicerae reddish brown, covered with whitish setae. Sternum 4.17 long, 3.76 wide, widest between coxae of second legs, dark brown with pale band in posterior half. AME diameter 0.36, PME diameter 0.32, AME separation 0.51, PME separation 1.07, PME–PLE separation 2.93, ALE–PLE separation 0.11. Clypeus height 1.22. Appendages: palps dark reddish brown.All leg segments uniformly dark reddish brown. Leg I femur 7.81, patella 4.21, tibia 6.15, metatarsus 7.55, tarsus 2.92. Opisthosoma 16.84 long, 14.94 wide, 5.08 high. Base color of dorsum light brown, with yellowish longitudinal band, covered with black spots, and with several small, pointy tubercules on anterior half and pair of large posterior tubercules, pointing posteriorly and protruding past spinnerets. Venter brown with several dark brown and black spots, two paler, grey, longitudinal bands. Epigynum as diagnosed (Fig. 4E).
Male (ARA1965 from Andasibe-Mantadia National Park, Madagascar, Fig. 4 G-M)
MEASUREMENTS AND COLORATION. Total body length 4.90. Prosoma 2.48 long, 2.37 wide, 2.12 high. Carapace and chelicerae dark reddish brown, covered with whitish to yellowish setae. Sternum 1.25 long, 1.14 wide, widest between coxae of second legs, orange, sparsely covered with white setae. AME diameter 0.23, PME diameter 0.21, AME separation 0.21, PME separation 0.49, PME–PLE separation 0.81, ALE–PLE separation 0.02. Clypeus height 0.42. Appendages: palps orange. Coxae, trochanters, and femurs orange, patellae, tibiae, metatarsi, and tarsi greenish orange. Leg I femur 3.20, patella 1.41, tibia 2.93, metatarsus 3.44, tarsus 1.26. Opisthosoma 3.46 long, 3.07 wide, 1.36 high. Base color of dorsum greenish brown, covered with black spots and areas, without small, pointy tubercules on anterior half. Venter greyish with black middle area and pair of white spots. Palp as diagnosed (Fig. 4K–M).
Variation
Female total length 18.9–25.1, prosoma length 7.65–8.55. Base color of opisthosoma dorsum light brown to dark brown, with anterior tubercules from small to pronounced. Some individuals with light median band, others without or with light anterior speck (Figs 4A, 6A). Males with little variation in appearance.
Distribution
Eastern Madagascar, known from Andasibe-Mantadia National Park (Toamasina Province), Ranomafana National Park (Fianarantsoa Province), and Marojejy National Park (Antsiranana Province).
Natural history
This species occurs in montane rainforests of eastern Madagascar. The web is typical of Caerostris (Gregorič et al. 2011a), suspended at day and night. Several individuals have embolic plugs in copulatory openings (Kuntner et al. 2015), but never more than one per copulatory opening.
description: Published as part of Gregorič, Matjaž, Yu, Kuang-Ping, Velez, Winny Rojas & Garb, Jessica E., 2025, Caerostris (Araneidae: Araneae) cryptic diversity highlights the need for taxonomic expertise in the genomic era, pp. 1-23 in European Journal of Taxonomy 989 on pages 8-11, DOI: 10.5852/ejt.2025.989.2877, http://zenodo.org/record/15303757