Mesabolivar huambisa Huber 2000
Creators: name: Huber, Bernhard A.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Pholcidae
Mesabolivar
Mesabolivar huambisa

description: Mesabolivar huambisa Huber, 2000
Figs 5–6, 26–31, 42–47
Mesabolivar huambisa Huber, 2000: 191, figs 738–747 (♂ ♀, Peru, Ecuador). [Machado 2007: 88; see Notes below].
Diagnosis. Easily distinguished from similar congeners (M. acrensis, M. maraba, M. pseudoblechroscelis) by screw-shaped sclerite prolaterally on bulbal process (Figs 29–31); also by shape of procursus (Figs 26–28; distinctive distal elements) and by shape of epigynum (Figs 42–47; median cavity very wide, not reaching anterior epigynal margin; lateral pair of processes directed towards ventral) (female of M. pseudoblechroscelis unknown).
Type material. PERU: Loreto: ♂ holotype, 21♂ 18♀ paratypes, MUSM, Rio Samiria (4°43’S, 74°18’W), v– vi.1990 (T. Erwin et al.), examined (Huber 2000; 1♂ 1♀ paratypes reexamined for present study).
Other material examined (all assigned tentatively; see Notes below). BRAZIL: Amazonas: 3♂ 1♀, ZFMK (Ar 18950), forest near Tabatinga (4.244°S, 69.92– 69.93°W), 90 m a.s.l., 2–4.xi.2016 (B.A. Huber, L.S. Carvalho); 1♀ in pure ethanol, ZFMK (Br 16-321), same data.
Pará: 2♂ (and 1♀ abdomen transferred from Br 16-226a), ZFMK (Ar 18951), Belém, Parque Estadual do Utinga, ‘site 1’ (1.424°S, 48.429°W), 25 m a.s.l., 6.x.2016 (B.A. Huber, L.S. Carvalho); 1♂ 1♀ (♀ abdomen transferred to ZFMK Ar 18951) in pure ethanol, ZFMK (Br 16-226a), same data.
Description (amendments; see Huber 2000). Males and females with pair of small brown marks behind ocular area. Male clypeus swollen and with sclerotized rim as in putative close relatives; male palpal tarsus with some bent hairs, one of them thicker than others; ventral membranous structure on bulbal process highly expandable (Fig. 29); femur 3 thicker than other femora (reexamined ♂ paratype with tibia 1 length 12.0, diameters of femora at half length: 0.20, 0.22, 0.30, 0.20).
Natural history. Both in Tabatinga and in Belém, the spiders were found on tree trunks, usually at about 0.5– 2 m above the ground. They built small domed webs with a diameter of only ~ 10–15 cm, with one side of the dome attached to the tree bark; here the spiders sat with the fontal side facing down. Males and females were sometimes seen to sit side by side.
Distribution. Possibly widely distributed from Peru and Ecuador (maybe Bolivia) to the estuary of the Amazon River (Fig. 723), but see Notes below.
Notes. The newly examined specimens differ slightly from the reexamined paratypes, but the significance of this variation is unclear. In males from Belém the tip of the procursus is less curved and the dorsal process is larger (Fig. 28); in males from both Belém and Tabatinga, the proximal part of the procursus is less curved ventrally (Figs 27, 28); in males from Belém, the screw-shaped sclerite on the bulbal process is smaller (Fig. 31); in females from both Belém and Tabatinga, the epigynal processes are more pointed (Figs 45, 47). In general, palps, chelicerae, and epigyna are smaller in specimens from both Belém and Tabatinga than in the paratypes, but sample sizes are small and leg length seems to be similar: tibia 1 in five newly examined males: 11.5–13.2 (mean 12.2); in one female: 6.7. Newly examined males tend to have thinner legs and less thickened femora 3 (diameters of femora at halflength in one male: 0.17, 0.18, 0.20, 0.17).
The specimens from Brazil (Acre) and Bolivia assigned to M. huambisa in Machado (2007) are also problematic. They were later considered to represent two new undescribed species (Machado 2011, “sp. 05” and “sp. 09”), but the drawings (I did not examine the specimens) of the Bolivian specimens strongly resemble the specimens from Belém.
In sum, species limits appear difficult to establish in this group, and future studies should aim at large scale geographic sampling and inclusion of molecular data.
In the original description of the female internal genitalia, “large membranous structures of unknown function reaching into lateral apophyses” were illustrated (Huber 2000: 194, fig. 745). These structures are silk glands and have no relation with the female genitalia (except for filling the available space in the epigynal processes).
description: Published as part of Huber, Bernhard A., 2018, The South American spider genera Mesabolivar and Carapoia (Araneae, Pholcidae): new species and a framework for redrawing generic limits, pp. 1-178 in Zootaxa 4395 (1) on pages 17-18, DOI: 10.11646/zootaxa.4395.1.1, http://zenodo.org/record/1202519