Rediscovery of Nuvol umbrosus Navás (Neuroptera, Chrysopidae, Leucochrysini): a redescription and discussion

Abstract The monotypic leucochrysine genus Nuvol was previously known from three specimens of Nuvol umbrosus Navás, collected in the Atlantic Forest region of Brazil. For many years these specimens have been missing, and the genus has remained without a modern description. Here, the species is redescribed based on two newly discovered specimens (females) from the Amazonian region. The female terminalia are relatively simple, except for the subgenitale, which is enlarged, folded into two sections, and heavily sclerotized. Unique aspects of the wing venation and the unusual pattern of banding on the wings support the retention of Nuvol as a valid genus within the Leucochrysini. There are differences between the Amazonian specimens studied here and the earlier descriptions based on specimens from the Atlantic Forest. These differences may indicate the presence of two distinct, geographically separated species within the genus. However, largely because we do not know the sexes of the earlier specimens, we are treating the differences discovered in the two female specimens as expressions of intraspecific variation.


Introduction
Leucochrysini (Neuroptera: Chrysopidae) is a large tribe of green lacewings restricted to the New World. Currently, it includes seven genera in varying states of systematic resolution. One of these genera, Nuvol, has received no modern taxonomic treatment: accurate drawings of the only included species, Nuvol umbrosus Navás, are available solely for the wings; its abdominal and genitalic features have not been described (Brooks and Barnard 1990). As a result, the generic distinction of this genus has remained in need of reevaluation for some time.
At the time of its description, the single type specimen of N. umbrosus remained in the Navás collection in Barcelona (Navás 1916); it and one other specimen that Navás (1929a, b) cited later from the Museum in Hamburg are lost (Monserrat 1985). And, unfortunately, the heretofore only known recent specimen of N. umbrosus [reported from the Museum of Zoology, São Paulo, Brazil, MZUSP; see Brooks and Barnard 1990] now also appears to be missing (C. A. Tauber & M. J. Tauber, pers. obs.). However, during 2014 the authors independently discovered two additional specimens of Nuvol -one (a female) in the collection of the Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Brazil, and another (a female) in the Utah State University Collection, Logan, Utah. Both specimens are similar, and at this time we are treating them as examples of Nuvol 's type species, Nuvol umbrosus Navás, 1916 (however, see below).
To help determine whether the genus should be retained as a valid entity within the Leucochrysini, the newly discovered Nuvol specimens are described and their features compared, including the taxonomically important genitalia, with those of other leucochrysines. Unfortunately, the generic placement of Nuvol will remain unresolved largely because our specimens are both females, and the male genitalia, as well as the larvae, are unknown.

Tribe Leucochrysini
The tribe Leucochrysini contains the seven genera and two subgenera listed below. Following each genus name are: (i) the number of species currently included in the genus and (ii) references to recent systematic work dealing with the genus.

Genus Nuvol Navás, 1916
Monotypic genus. Type-species: Nuvol umbrosus Navás, 1916. Known geographic distribution. Brazil: States of Rio de Janeiro (RJ), São Paulo (SP), Amazonas (AM), Rondônia (RO), as follows. RJ: type specimen reported in original description, Rio de Janeiro, II-1912 (Navás collection, specimen missing); subsequent specimen reported from Prov. Rio de Jan., 20.X.1906, Coll. V. Bönninghausen. M. H., (Navás 1929a, b; Hamburg Museum, probably destroyed during WWII); SP: Alto da Serra, ii-II (or XII)-28, R. Spitz leg (examined by Adams' at the MZUSP, without abdomen, specimen apparently missing); AM: Novo Aripuanã 05°15'53"S / 60°07'08"W. Type. The original description states that the type specimen was collected in "Rio de Janeiro, Febrero de 1912" and that it was retained in the Navás collection. The specimen is not reported to be in the Navás collection now (Monserrat 1995). At some time, a neotype should be designated for this species. However, we are not doing so with either of the two extant specimens because: (1) They are both from the Amazonian region of Brazil, far removed from the type locality -the Atlantic Forest region of Rio de Janeiro. (2) Our specimens are both females; the sexes of the previously described species are unknown. (3) Our specimens both differ significantly from Navás' illustration and description in aspects of the fore and hind wing venation (discussed below). Thus, until male and female specimens from near the type locality are available for comparison, we consider it prudent to withhold from designating a neotype.
Wings (Fig. 4): Forewing 14.8-15.8 mm long, 5.1-5.5 mm wide (at widest point); ratio of length: maximum width = 2.9:1. Costal area relatively narrow; tallest costal cell (#6-8) 0.8 mm tall, 1.4-1.8 times width, height 0.17-0.15 times width of wing (midwing). First intramedian cell ovate, height (along median arculus) 0.33 mm, width 2.5-2.6 times height, 0.65-0.66 times width of third median cell. First radial crossvein distal to origin of radial sector (Rs); radial area (between radius and Rs) with single row of 15 closed cells; tallest cell (#6-8) 1.3-1.5 times taller than wide. Base of subcosta, upper media, lower media slightly crassate, other longitudinal veins robust; 4 b cells (= cells beneath Rs, not including an inner gradate vein). Seven to nine discrete inner gradates in irregular pattern, outer gradates apparently aligned with distal vein- lets in smooth, curved line paralleling margin of wing from tip of pseudomedia (Psm) to tip of Rs. Height of fourth gradate cell 2.9-3.9 times width. Six to seven b' cells (cells beneath Psm after second intramedian cell). Four intracubital cells (three or four closed). Subcosta, radial sector forked apically; almost all other apical veins unforked. Membrane with four large, conspicuous yellow to brown marks; stigma with dark brown marks basally, distally. Veins mostly pale, except under markings. Hindwing 13.1-13.8 mm long, 4.1-4.3 mm wide. Six discrete inner gradates, outer gradates similar to those of forewing; 13-15 radial cells (counted from origin of radius, not false origin). Five large b cells (no small "t" cell); six b' cells beyond second intramedian cell; two intracubital cells (one closed). Membrane with yellow to light brown marks, similar to those on forewing; stigma with single dark brown mark basally. Veins pale except near stigmal marking.

Discussion
Nuvol 's generic relationships. In the original description (Navás 1916) and in subsequent discussion (Brooks and Barnard 1990), N. umbrosus was said to resemble Leucochrysa, but also to differ from it in several features of the wings: notably an elongate radial vein that parallels the costa and curves posteriorly at the tip of the wing, outer gradates aligned with the bases of the distal veins in a smooth line that parallels the wing edge, an elongate stigma, four intracubital cells in the forewing, and distinctive markings on the fore and hind wings. These characters were all present in the specimens described herein, and, other than the four intracubital cells that also are present in Berchmansus (Tauber 2007), they readily distinguish Nuvol specimens from those in other leucochrysine genera.
At this time when the anatomy of females from only a small percentage of leucochrysine species has been described, our study does not provide any novel insights into the relationships of this species with other leucochrysines. The internal genitalic structures of the Nuvol female are relatively simple, and they lack the complex, coiled bursal duct of Berchmansus. Thus, they resemble those known for females in a large number of other leucochrysine species. However, the heavy sclerotization and folding of the subgenitale are conspicuous and may be distinctive among leucochrysines. Thus, at this time, there is no compelling evidence that supports a change in the generic designation of Nuvol, and we consider that the external features above provide substantive evidence for a generic difference between Nuvol and other leucochrysines. We await the discovery of Nuvol larvae and broadly based comparative adult morphological and/or molecular studies of the Leucochrysini before making any generic level changes.
Specific identity. It is noteworthy that the two Amazonian specimens we studied differed somewhat from the images and descriptions of the Atlantic Forest specimens studied by Navás (1916) and Adams (via Brooks and Barnard 1990). Specifically, the degree of supression in the forking of the apical veinlets is much stronger in the Amazonian than in the Atlantic Forest specimens. Illustrations by Navás (1916, fig. 6) and Adams (fig. 519 in Brooks and Barnard 1990) of the Atlantic Forest species show forewings with 16 and 14 forked apical veinlets; only four or five of the anterior radial veinlets are unforked. However, in the Amazonian specimens none or only one of the apical veinlets is forked. The difference also occurs in the hind wings. In addition, there seem to be some differences in the head and thoracic markings between our specimens and those described by Navás.
Although it is quite possible that the above venational and color differences are expressions of interspecific variation, at this time we cannot exclude intraspecific, i.e., geographic or sex-associated variation. Our two Amazonian specimens are females; whereas the sexes of the specimens from the Atlantic Forest are unknown. And we note that leucochrysines are notorious for polymorphisms in body color and markings (Mantoanelli et al. 2006, Tauber et al. 2011b, Tauber et al. 2013a. Thus, until the discovery of additional specimens, the two studied herein should be considered as variants of one species.

Modifications for Brooks and Barnard's (1990) key to adults of chrysopid genera
In the most recent taxonomic key for chrysopid genera (Brooks and Barnard 1990), Nuvol females could be recovered with small alterations to couplets 82 and 83, and the addition of another couplet, as follows below. Please note: Except where noted, the figure numbers below are those of Brooks and Barnard 1990).