A new species of Alpaida ( Araneae , Araneidae ) from Caxiuanã National Forest , Oriental Amazonia , Brazil

Alpaida guto n. sp. is described based on males and females from State of Pará, Brazil. This species appears to be the most abundant Alpaida O. P.-Cambridge, 1889 species in Caxiuanã National Forest, eastern Amazonia. The males seem to be close to A. antonio Levi, 1988 but can be easily distinguished by the terminal apophysis with rounded distal lobe and long, slender basal prong; females differ from those of A. yotoco Levi, 1988 by the median lobe with a basal constriction and by the bilobed median plate.

The genus Alpaida O. P.-Cambridge, 1889 is composed by diurnal orb-weaver spiders occurring only in Neotropical region.Species of this genus are recognized by the bright, glabrous body; male palp with radix, embolus and terminal apophysis fused; mushroomshaped paramedian apophysis with stalk attached to the conductor.Females are recognized by the shape of the epigynum which is usually transverse and sclerotized, with posterior lips; middle portion drawn out into a triangular lobe or scape; copulatory openings on each side between plate and lips (LEVI, 1988).LEVI (1988) presented an extensive revision of the genus, redescribing 40 previously known species, which were scattered in various Araneidae genera, and describing 94 new species, totalizing 134 species.Although the author had estimated that the actual richness of the genus could reach 300 species, only two additions to the taxonomy of the genus were made after his revision: LEVI (1992) redescribed A. tullgreni (Caporiacco, 1955), originally proposed in Parawixia F. P.-Cambridge, 1904, andBUCKUP &MEYER (1993) described the hitherto unknown male of A. scriba (MELLO-LEITÃO, 1940).
The new species of Alpaida herein described occurs in several localities inside the Caxiuanã National Forest, mainly in the Ferreira Penna Scientific Station and in the PPBio parcel at Caquajó Creek, a tributary of the Anapú River.However, an isolated record in the Metropolitan area of Belém (Santa Barbara Municipality), nearly 400 kilometers from Caxiuanã, is also reported.

MATERIALS AND METHODS
The specimens examined are deposited in the collections of Museu Paraense Emílio Goeldi (MPEG), Belém, Pará (Curator: A. B. Bonaldo) and Museu de Ciências Naturais (MCN), Fundação Zoobotânica do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul (Curator: E. H. Buckup).The methods used to make illustrations and measurements were the same used by LEVI (1985,1988).The palp was illustrated in mesal view and the epigynum in both ventral and posterior views.All measurements are in millimeters.Etymology.The specific name is patronym in honor of arachnologist José Augusto Pereira Barreiros, nicknamed Guto (in memoriam), who collected some of the specimens studied here as well as several other spider samples in Caxiuanã National Forest.

Alpaida guto
Diagnosis.The male of Alpaida guto n. sp.resembles those tentatively attributed by LEVI (1988) to A. antonio Levi, 1988 by the terminal apophysis with distal lobe strongly folded, projected beyond the cymbium (see LEVI, 1988, figs. 396, 397); differs by the terminal apophysis with larger, rounded distal lobe and long, slender basal prong; median apophysis wider, duckshaped (Fig. 1).Females are similar to those of A. yotoco Levi, 1988 by the large epigynal lips which are wider than median plate in posterior view (see LEVI, 1988, figs. 579-582); differs by the median lobe with a basal constriction (Fig. 3) and by the bilobed median plate (Fig. 4).
Description.Male (Holotype): Carapace, legs, endites and chelicera yellow.Eyes ringed in black.Sternum yellowish with median black longitudinal line.Dorsum of abdomen yellow with two lateral pairs of black patches and posterior black mark; venter yellowhish without pigment except for a median dusky patch.Palp with four long macrosetae on mesal edge of cymbium, extended towards the embolus tip and conductor.Total length 3.0.Carapace 1.6 long, 1.2 wide.First leg: femur 1.9; patella and tibia 2.2; metatarsus 1.6; tarsus 0.6.Second patella and tibia 1.7; third 1.1; fourth 1.5.
Variation.Males (n = 10): total length, 2.8 -3.9; females (n = 10): total length, 3.5 -4.8.Males may present the same dorsal color pattern in the abdomen as in females, depending on the amount of deposited guanine; the macrosetae number on mesal edge of cymbium varies (3 at 5).Some female present a median dusky patch on the venter of abdomen.Natural History.Alpaida guto n. sp.appears to be the most abundant Alpaida species in Caxiuanã National Forest, reaching nearly 50% of all adult Alpaida specimens so far obtained in the PPBio parcel; considering all samples available from Caxiuanã Natural Forest, this species reaches nearly 20% of all Araneidae specimens collected in this area until now.It has been collected in nearly two meters high trees and small bushes, mainly during the rainy period, using beating tray, sweep net and manual nocturnal looking up collecting methods.