Iuiuia caeca sp. n. (type locality: Brazil, Bahia State, Iuiu municipality).

Small kinnarid (ca. 3 mm body length), strongly troglomorphic: compound eyes absent, tegmina reduced, wings vestigial, body pigmentation reduced (Fig. 3). Iuiuia gen. n. can be distinguished from all other kinnarid genera by the unique combination of the following characters: vertex wide and short; male genitalia with genital segment in caudal aspect approximately in a figure-8-shape; anal segment short, ventrally on each side with a distinct wing-shaped compressed process; parameres slender, narrow throughout, medially converging; aedeagus tubular, stout, periandrium with two large, lateral lobes. Iuiuia gen. n. differs conspicuously from Kinnapotiguara (Hoch & Ferreira, 2013) in the configuration of the male genitalia (Hoch and Ferreira 2013: Figs 4, 5–10): genital segment with caudal margin smooth (vs caudal margin with lateral processes in Kinnapotiguara); anal segment with two short, wing-shaped lateroventral processes (vs anal segment with two pairs of slender processes in Kinnapotiguara); parameres narrow, slender throughout, medially converging (vs parameres differentiated into three processes in Kinnapotiguara) and aedeagus with two large lateral lobes (vs aedeagus without lateral processes in Kinnapotiguara).

Head. Vertex trapezoidal, short, ca. 3 × wider posteriorly than medially long, with a very faint median carina; anterior and posterior margin of vertex parallel. Frons narrow, ca. 1.8–2.0 × longer than maximally wide, widest between level of antennae and frontoclypeal suture, ca. 1.3 × longer than post- and anteclypeus together, surface medially smooth, devoid of a median carina, lateral margins distinctly ridged. Frontoclypeal suture nearly straight. Post- and anteclypeus with a distinct median carina. Rostrum elongate, in repose well surpassing hind coxae, third joint shorter than second. Compound eyes absent, their former position recognizable by a shallow, vaulted area. Median (frontal) ocellus absent, lateral ocelli vestigial. Antennae with scape short, subcylindrical, slightly expanding distally; pedicel subcylindrical, ca. 2.4 × as long as wide, with distinct sensory plaque organs; arista ca. 2.8 × as long as pedicel.

Thorax. Pronotum tricarinate, ca. 3 × wider than vertex posteriorly, short, posterior margin medially shallowly concave; carinae distinct, median carina attaining but not surpassing anterior margin of pronotum; lateral carinae medially more or less parallel to posterior margin, and joining posterior margin laterally. Mesonotum faintly tricarinate, ca. 1.3 × wider than medially long. Tegulae vestigial. Hind tibiae laterally unarmed, distally with 7 slender teeth, arranged in a shallow arc. First metatarsal joint distally with 4/5 and 5/6, 2nd metatarsal joint with 3/4 or 4/5 teeth (individually and bilaterally variable). Pretarsal claws and arolia small, inconspicuous. Tegmina (Fig. 4) comparatively short, very shallowly tectiform, almost flat, in repose, in males either slightly shorter than tip of abdomen (parameres), or just reaching tip of abdomen, or slightly surpassing it; in females slightly shorter than tip of abdomen (dorsal margin of gonocoxae VIII); venation in proximal portion as in epigean Kinnaridae with a large and wide subcostal cell; clavus cixioid (sensuEmeljanov 1984), i.e., common claval vein (Pcu and A1) reaching hind margin of clavus (vein A2); basal cell of forewing closed by anastomosis of M and CuA, without conspicuous arculus; tegmen distally of nodal line distinctly reduced and variable among specimens with 6 distal marginal cells, partly incompletely delimited due to reduced distal marginal veins. Hind wings vestigial, very short, venation strongly reduced.

Figure 4. 

Iuiuia caeca sp. n. Left tegmen, male (paratype). Scale bar 0.1 mm.

Male genitalia. Genital segment bilaterally symmetrical, in lateral aspect short, ca. 3 × as high as medially long; in caudal aspect approximately figure-8-shaped, in upper third laterally constricted, with a narrow transversal bridge; anterior margin of genital segment smooth, without any conspicuous median apodemes; medioventral process prominent, broadly subtriangular, in lateral aspect distinctly exceeding caudal margin. Anal segment bilaterally symmetrical, short, stout, ventrally on each side with a compressed wing-shaped process. Parameres slender, narrow throughout, medially converging. Connective straight, narrow, almost terete.

Aedeagus bilaterally symmetrical, tubular, stout; periandrium with two large lateral lobes; proximal apodeme of aedeagus (= „tectiform structure“: term applied by Bourgoin 1997 for Meenoplidae) slender, with dorsal and ventral margins rapidly diverging, proximal margin rounded.

Females with abdominal tergites VI, VII and VIII bearing wax-fields. Female genitalia as in other Kinnaridae of the non-piercing type; sternite VII broadly rectangular, caudal margin straight; caudal margin of sternite VIII medially deeply incised; gonocoxae VIII bilobate, both lobes well developed, apically converging.

The genus name refers to Iuiú, the name of the municipality were the cave (type locality) is situated. The gender is feminine.

Habitus (Fig. 3). Strongly troglomorphic species, predominantly yellowish body pigmentation, compound eyes and ocelli absent, dorsoventrally compressed body shape, tegmina short, in repose slightly surpassing tip of abdomen, wings vestigial.

Body length. Measurements refer to distance between anterior margin of head to tip of abdomen (= caudal margin of parameres), those in brackets to distance of anterior margin of head to distal margin of tegmina.

Males. 2.8 (3.4)–3.8 (3.8) mm (n = 8). Females. 4.4 (4.0)–4.5 (4.1) mm (n = 2).

Colouration. Frons, vertex, pronotum yellowish, carinae contrasting dark brown; mesonotum more or less uniformly sordid yellowish; antennae and tegulae sordid light brown; tegmina translucent, uniformly yellowish-brown, veins slightly darker, without any conspicuous pattern. Metanotum, legs, as well as abdominal tergites and sternites pale yellow.

Configuration, shape and proportions of head and thorax as described for the genus.

Male genitalia (Fig. 5). Genital segment as described for the genus. Anal segment bilaterally symmetrical, short, in dorsal aspect subquadrangular, ventrally on each side with a wing-shaped, compressed lobe which is caudally rounded, cephally subacute and ventrally slightly curved medially. Parameres slender, medially concave, distally curved dorsomedially. Aedeagus bilaterally symmetrical, stout, tubular, central portion of periandrium distinctly constricted at ca. half its length, distally on its ventral side rapidly tapering into a helmet-shaped, bilobal structure with phallotreme apically; phallotreme in repose exposed dorsocaudally; periandrium smooth, without any spinose processes, but with two large lateral lobes which are ventrally broadly rounded, and dorsally – in their basal half – deeply concave.

Figure 5. 

Iuiuia caeca sp. n. Male genitalia (paratype). a genital segment, left lateral aspect; b same, caudal aspect; c anal segment, left lateral aspect; d same, caudal aspect; e parameres, caudal aspect; f left paramere, left lateral aspect; g aedeagus with connective, left lateral aspect; h same, ventral aspect; j same, dorsal aspect. Scale bars: 0.1 mm.

External female genitalia (Fig. 6). Sternite VII in ventral aspect broadly rectangular, ca. 2.5 times as wide as long, lateral margins straight, more or less parallel, caudal margin smooth, more or less straight; sternite VIII in ventral aspect stout, in anterior portion ca. 3 times as wide as long, caudal margin medially deeply incised cephally; gonocoxae VIII bilobate: ventral lobe in lateral aspect tongue-shaped and apically rounded, dorsal lobe more strongly developed than ventral lobe, distally tapering into an acute tip pointing medioventrally; both lobes beset with setae. Tergite IX narrrow, dorsally short, laterally slightly expanding caudally. Anal segment (segment X) in dorsal aspect proximally narrow, distally expanding laterally, caudal margin in ventral aspect deeply concave. Anal style (segment XI) comparatively large, paraproct narrow, elongate, epiproct rounded, caudally not surpassing paraproct.

Figure 6. 

Female abdomen and external genitalia. a ventral aspect, b right ventrolateral aspect. Abbreviations: s VII = Vll. sternite, gx VIII = gonocoxae VIII; as (X) = anal segment (X. segment); ast (XI) = anal style (XI. segment); t VI, t VII, t VIII = tergites of segments VI-VIII. Scale bar 0.1 mm.

The species is only known from the “Lapa do Baixão” cave in Iuiú municipality, Bahia State, Brazil. The external vegetation in the area corresponds to the “Caatinga” formation, the only xeric biome of the country, with xeromorph, decidual vegetation (Fig. 2A).The cave has not been completely explored, since part of its inner chambers become flooded during rainy periods. However, the known passages extend over 500 meters. The only known entrance is a small opening (around 1m² – Fig. 2B), which clearly imposes a huge stability to the cave atmosphere. During different surveys in the Iuiú municipality, another eight caves located near Lapa do Baixão cave were also sampled, but no specimen of Iuiuia caeca was found. This strongly suggests that the species is endemic to this cave. Furthermore, this cave was visited five times, and specimens we only found during two visits, which may suggest the low abundance of the species. However, during our last visit to the cave on 9.vii.2014, several adults and nymphs were observed, though they were restricted to a small part of the cave (see “Ecology”).

The “Lapa do Baixão” cave formed within limestones from the “Bambuí” geological group, from the Neoproterozoic, with ages ranging from 650-850 Myr. This group comprises the largest limestone formation in Brazil, embracing most of the known Brazilian limestone caves (Fig. 1). The other two troglobitic planthoppers described from Brazil are Kinnapotiguara troglobia (Hoch & Ferreira, 2013) (Kinnaridae), from limestone caves from the “Apodi” group (Rio Grande do Norte state), and Ferricixius davidi (Hoch and Ferreira 2012) (Cixiidae), known from a single iron ore cave in the “Iron quadrangle” formation (Minas Gerais state) (Fig. 1). The Apodi group comprises limestones from the Cretaceous (around 100 Myr), while the “Iron quadrangle” is much older (around 2.4 Byr).

The Baixão cave possesses dozens of roots, mainly observed in the first portion of the cave (Fig. 2D). This part of the cave adjacent to the entrance comprises a labyrinth-like system of interconnected passages; then narrows into a single vadose and semi-meandrine passage. This deep vadose passage lacks roots, and no specimens of Iuiuia caeca were observed there.

Unfortunately, it was not possible to associate the roots to any particular plant species in the surface vegetation, but considering the distance between the surface and the cave, it appears likely that such roots belong to substantial trees with pivotant roots systems, capable of penetrating deep inside the cracks into the soil and rock until reaching the cave chambers.

Such roots shelter a variety of invertebrate species which feed especially in their decomposing parts. However, also many non-troglomorphic Cixiidae (Pintalia spp.) feed on them, especially in those roots located nearer the entrance (but also in aphotic zones). These are supposedly accidentals to the cave, but eventually can become troglophiles. Specimens of Iuiuia caeca were observed only on roots within the labyrinthic part in the deep cave zone.

They were only rarely observed on the same roots where the non-troglomorphic Cixiidae occur. The root mats where Iuiuia occur are mainly placed in the final portion of this labyrinthic part of the cave, near the connection with the inner single vadose and semi- meandrine passage. Such root mats are considerably smaller than those found in other parts of the cave. During a visit to the cave on 7.viii.2013, most of the observed specimens were nymphs, and only three adult males were found. During this visit, one of the males was found on a small root, near the cave floor, while the other two were found in an upper chamber, without roots, where they were freely walking on speleothems. During our last visit to the cave (9.vii.2014), seven adults and many nymphs were observed, but their spatial distribution was even more restricted. All observed specimens were associated with roots in a single part of the conduit, and no specimens were found in other chambers, as in the previous visit. Since both visits occurred in the dry period of the area, such differences observed on their abundance and distribution cannot be primarily related to seasonal changes. Potential predators include spiders (especially Ochyroceratidae), Amblypygi (Charinus iuiu Vasconcelos & Ferreira, 2016) and a relatively large troglobitic pseudoscorpion species, with a body size of around 5 mm (Spelaeobochica iuiu Ratton, Mahnert & Ferreira, 2012); the latter is well distributed throughout the cave, but less common in the areas where I. caeca occurs.

The species epithet “caeca” (blind, Lat.) refers to the complete reduction of compound eyes in this species. The gender is feminine.

Holotype male. Brazil. Bahia State, Iuiu municipality, Toca Lapa do Baixão (14°23’8.13”S, 43°37’35.06”W), 7.viii.2013, R.L. Ferreira leg., in coll. Universidade Federal de Lavras, ISLA.

Paratypes: 2 males, same data as holotype. 5 males, 2 females, same data as holotype, except 9.vii. 2014, in coll. Universidade Federal de Lavras, ISLA.

In the cave, several 4th and 5th instar nymphs of Kinnaridae were collected which, due to substantial morphological differences, apparently represent two species. However, none of these nymphs could be associated with certainty to Iuiuia caeca. Thus it is likely that the cave Toca Lapa do Baixão houses at least two, if not three, kinnarid species.