Mesabolivar acrensis Huber 2018, sp. n.

Mesabolivar acrensis sp. n. Figs 1–2, 13–15, 18–22, 32–38 Diagnosis. Males are easily distinguished from most known congeners by shape of procursus (Fig. 14; distinctively widened and strongly curved distal element; very similar in M. pseudoblechroscelis; compare Fig. 14 with figs 5.07–08 in Machado 2011); from two most similar species (M. pseudoblechroscelis, M. maraba) also by bulbal process (Fig. 15; shape of distal structures); from most species (except M. pseudoblechroscelis, M. maraba, M. huambisa) also by armature of male chelicerae (Figs 18–19; pair of slender apophyses, straight in lateral view), and by shape of epigynum (Figs 20–21, 32–37; large median depression, lateral margins slightly diverging towards anterior, bordered posteriorly by large pocket; pair of conical lateral processes directed slightly towards posterior - epigynum possibly indistinguishable from M. maraba, due to variation, see below); from M. maraba and other putatively close relatives also by female internal genitalia (Figs 22, 38; elongated pore-plates converging towards posterior) (female of M. pseudoblechroscelis unknown). Etymology. The specific name is an adjective derived from the type locality. Type material. BRAZIL: Acre: ♂ holotype, 1♀ paratype, UFMG (21497–98), 2♂ 23♀ paratypes, ZFMK (Ar 18942–43), Rio Branco, Reserva Florestal Humaitá (9.749°S, 67.666°W), 180 m a.s.l., 28.x.2016 (B.A. Huber, L.S. Carvalho). Other material examined. BRAZIL: Acre: 1 juv., together with paratypes; 1♀ 3 juvs in pure ethanol, ZFMK (Br 16-309), same data as types. 2♂ 17♀, ZFMK (Ar 18944), Rio Branco, Fazenda Experimental Catuaba (10.08°S, 67.625°W), 225 m a.s.l., 26–27.x.2016 (B.A. Huber, L.S. Carvalho); 2♀ in pure ethanol, ZFMK (Br 16- 306), same data; 1♂ 8♀, ZFMK (Ar 18945), Rio Branco, Fazenda Experimental Catuaba (10.078°S, 67.619°W), 200 m a.s.l., 29.x.2016 (B.A. Huber, L.S. Carvalho). Assigned tentatively. BRAZIL: Acre: 3♂ 10♀ 2 juvs, ZFMK (Ar 18946), Cruzeiro do Sul, forest near airport (7.596°S, 72.767°W), 200 m a.s.l., 30.x.2016 (B.A. Huber, L.S. Carvalho, E.O. Machado); 1♀ 1 juv. in pure ethanol, ZFMK (Br 16-313), same data. Amazonas: 3♂ 2♀, ZFMK (Ar 18947), Guajará, forest at Fazenda Colorado, ‘site 2’ (7.528°S, 72.655°W), 210–240 m a.s.l., 31.x.2016 (B.A. Huber, L.S. Carvalho, E.O. Machado). Description. Male (holotype) MEASUREMENTS. Total body length 2.3, carapace width 1.05. Distance PME-PME 120 µm, diameter PME 110 µm, distance PME-ALE 80 µm, distance AME-AME 30 µm, diameter AME 45 µm. Sternum width/length: 0.80/ 0.55. Leg 1: 30.1 (7.1 + 0.5 + 7.2 + 13.5 + 1.8), tibia 2: 4.7, tibia 3: 3.4, tibia 4: 5.0; tibia 1 L/d: 76. Femora 1–4 width (at half length): 0.14, 0.15, 0.15, 0.15. COLOR (in ethanol). Carapace ochre-yellow, with barely visible darker median mark, ocular area also slightly darkened; sternum orange; legs ochre to light brown, with indistinct darker rings on femora (subdistally) and tibiae (proximally; subdistal rings barely visible), tips of femora and tibiae lighter; abdomen greenish-gray, with dark internal marks dorsally and laterally, without ventral mark. BODY. Habitus as in Fig. 1; ocular area raised (higher than usual in genus); carapace with distinct median furrow; clypeus slightly swollen and whitish, with sclerotized margin; sternum unmodified. CHELICERAE. With pair of long, slender apophyses, straight in lateral view (Figs 18–19). PALPS. As in Figs 13–14; coxa with conical retrolateral apophysis; trochanter with retrolateral apophysis; femur very large, proximally with retrolateral apophysis and prolateral hump set with short hairs; tarsus with small dorsal processes, with one strong and several regular hairs bent towards dorsal (Fig. 14); procursus distally widened and strongly curved towards dorsal, with large ventro-distal sclerite separated from proximal part by whitish area; bulbal process with distinctive distal structures (Fig. 15). LEGS. Without spines and curved hairs, few vertical hairs (i.e. short hairs perpendicular to leg segment); retrolateral trichobothrium on tibia 1 at 2.5%; prolateral trichobothrium present on tibia 1; tarsus 1 with ~25 pseudosegments, distally fairly distinct. Male (variation). Males from Cruzeiro do Sul and Guajará appear identical in shape to those from Rio Branco, but the light area of the procursus is transparent rather than whitish and the black ventro-distal sclerite is slightly narrower (but the width of this sclerite is variable even among specimens from Rio Branco). Tibia 1 in six males from Rio Branco (incl. holotype): 6.4–9.2 (mean 7.7); in five males from Cruzeiro do Sul and Guajará: 8.8–10.3 (mean 9.6). Female. In general similar to male (Fig. 2) but carapace ochre-brown rather than yellow to orange, with larger brown median mark; ocular area slightly lower than in males; dark rings and whitish tips of femora and tibiae more distinct; clypeus less swollen and margin not sclerotized. Tibia 1 in 44 females from Rio Branco: 3.5–5.1 (mean 4.3). Epigynum as in Figs 20–21 and 32–33; anterior plate with large median depression bordered posteriorly by large pocket; pair of conical lateral processes directed slightly towards posterior; posterior plate large, simple. Internal genitalia as in Figs 22, 38, with elongated pore-plates converging towards posterior and distinctive median dark anterior structure. Females from Cruzeiro do Sul and Guajará tend to have slightly longer and more pointed epigynal processes and slightly narrower median depressions; however, this varies even within localities (Figs 34–37). As in males, females from Cruzeiro do Sul and Guajará tend to have longer legs: tibia 1 in 11 females: 4.8–5.9 (mean 5.5). Natural history. The spiders were found close to the ground, in webs that were mostly hidden in the leaf litter, under logs, or in small cavities in the ground. A small part of the domed sheet was visible from outside, and turned into a funnel towards the back, where the spider(s) were hiding. When disturbed, they vibrated rapidly with small amplitude or tried to run away. Distribution. Known from two localities near Rio Branco and from two localities near Cruzeiro do Sul in Acre and Amazonas states (Brazil) (Fig. 722).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 10-16, DOI: 10.11646/zootaxa.4395.1.1, http://zenodo.org/record/120251