First description of the female of the jumping spider Balmaceda nigrosecta Mello-Leitão (Salticidae, Dendryphantini, Marpissina)

Abstract The female of Balmaceda nigrosecta Mello-Leitão, 1945 is described and illustrated for the first time. In addition, this paper further illustrates the male, and provides the first known observations on the natural history of this species, including habitat, cohabitation, and prey capturedata.


Introduction
Jumping spiders (Salticidae) constitute a relatively young family, which has rapidly radiated (Bodner and Maddison 2012;Hill and Edwards 2013). This is the largest family of spiders, with 5838 described species (WSC 2015). However, one major problem is that this diversity may be hyper-inflated due to lack of matching of singlesex known species (Edwards 2014). This problem, in part, may have contributed to some quantitative inconsistencies between salticid databases, as observed among those of Prószyński (2015), the WSC (2015), and Metzner (2015). In Prószyński's database, accepted species status means that both sexes are adequately described and illustrated, while incomplete is due to the description and illustration of only one sex. A proposal for matching sexes was given by Edwards (2014) that consists in searching for an autapomorphy shared by both sexes as an intraspecific counterpart to an interspecific synapomorphy, considering also geographical and other data in an analysis (Edwards 2014). Use of this methodology is strengthened when the species in question belongs to a group that is already well-defined by morphology that agrees with its phylogenetic placement based on molecular data, e.g. Marpissinae (Maddison et al. 2014) [recently reclassified as Subtribe Marpissina (Maddison 2015)].
The marpissine genus Balmaceda Peckham & Peckham, 1894 is exclusive to the Americas. It currently includes eight valid species (WSC 2015;Metzner 2015), of which only the type species is known for both sexes, and five are known only for male or female (WSC 2015; the sixth is a nomen dubium). The latter is the case for B. nigrosecta Mello-Leitão, 1945. These spiders are similar to other marpissines as Metacyrba and Platycryptus (see Edwards 2006) in body and external genitalia forms. There is also some similarity to the euophryine Corticattus in the body form, but an examination of the genitalia can easily distinguish them (see Zhang and Maddison 2012).
In recent surveys of the salticid fauna from Misiones, in Northeastern Argentina (Rubio 2014), males and females of B. nigrosecta were observed and collected together. The coexistence of male and female in the same retreat observed in the field provided definitive evidence for conspecificity in our samples. In this paper, the female of B. nigrosecta is described for the first time and its somatic and genital morphology is illustrated. Some data on natural history are also presented.

Methods
Field observations of living specimens were made in Misiones Province, Northeastern Argentina. Specimens were collected on walls of brick houses in Iguazú National Park and peri-urban habitats of Puerto Iguazú. This area corresponds to the Upper Parana Atlantic Forest Eco-region (Olson et al. 2001).
Morphological terms and description formats follow the main recent works about marpissines (Edwards 2006) and similar jumping spiders (Ruiz and Brescovit 2013). Female genitalia were cleared in clove oil to study the internal structures after digestion in a hot 10-20% KOH solution (Ramírez 2014). Temporary preparations were examined using a Leica DM500 compound microscope and a Leica M60 stereomicroscope. All measurements are in millimeters, and were obtained with an ocular micrometer following Ruiz and Brescovit (2013). Leg segments are measured for length, except the first two femora and tibiae which are measured length x width. Photographs in nature were taken with a Nikon D80 digital camera using a Micro-Nikkor 85 mm lens. Specimens examined are deposited at the arachnological collections of the Instituto de Biología Subtropical, Misiones (IBSI-Ara, G. Rubio).
atrium, with the copulatory openings (CO) farther apart, anteriorly concave, and nearly transverse in orientation (B. picta has the COs nearly touching, anteriorly convex, and strongly oblique in orientation), and a thinner and curved male retrolateral tibial apophysis (Figs 1, 4, 5;compare with Edwards 2006: figs 116, 121, 122, 126). Also, the "W" shaped transverse mark across the middle of the abdomen is distinctive for both sexes, as only the lateral parts of this mark are evident and the medial connecting parts are absent for B. picta. It can be distinguished from B. reducta by having the copulatory ducts (CD) contiguous along the mid-line of the body in the middle of the duct (Fig 5; compare with Chickering 1946: fig 47).
Comments. From the illustrations in the original description it is clear that this species is very closely related to B. reducta (Chickering 1946: 64), and B. nigrosecta possibly is a senior synonym of B. reducta. Because the known distribution of B. reducta is limited (Panama) and far from Argentina, no synonymy will be made, as the genus is not yet adequately sampled in the region.
Because we note that the morphological data are quite similar among members of the genus, it is difficult to establish an intersexual autapomorphy (see Edwards 2014) for B. nigrosecta. Nevertheless, it appears that the irregular W-shaped mark in the middle of the abdominal dorsum is a species shared autapomorphy(Figs 6-11). Sex matching is also supported by geographic and phenological evidence, and by an instance of both sexes cohabiting in the same retreat, where an adult male and an adult female were found together.
Natural history. Balmaceda nigrosecta has sexual dimorphism as frequently occurs in other salticids, althoughstrong dimorphism is uncommon in marpissines. In this case the sexual dimorphism is weak; the males only show a slightly darker color in palps and first pair of legs. They live in many parts of the peri-urban area (Fig 12), even on light poles. They make a flat retreat or nest, about 15 mm long, always placed perpendicular to the ground, between 1 and 2 meters above ground (Figs 13-17). The entrance opening can be on either side. Spiders are positioned at the entrance, with the carapace leaning out (Figs 15, 16), usually looking down (as figure 16). In fiftyone observations, we saw them hunt in the same way: locate prey from the retreat or while actively searching (sometimes we observed them walking in the vicinity of the retreat in search of prey); when they detected something moving, they would accelerate towards it. Here one of two things would happen: if it was an unpalatable prey (e.g. an ant), spiders did not attack and returned quickly to the retreat; but if it was a potential prey, the spiders accelerated a definite distance, about 10 body lengths, and then lowered themselves close to the substrate, and continued approaching very slowly, like a cat stalking, then jumped extremely quickly over the prey. The catch was always observed to be successful, in one movement.
Distribution. Only known from northeast Argentina, in Misiones Province.
edge Wayne P. Maddison and Galina N. Azarkina for their constructive feedback on this manuscript. G.D. Rubio is Career Researcher of CONICET. This publication is funded by the "Fondo para la Investigación Científica y Tecnológica" (FONCyT): grant PICT-2013-1664 given to GDR.