Nyx Harbach & Linton

Harbach, Ralph E., Kitching, Ian J., Culverwell, C. Lorna, Howard, Theresa M. & Linton, Yvonne-Marie, 2013, Nyx pholeocola, a new genus and cavernicolous species of tribe Aedini (Diptera: Culicidae) from southern Thailand based on morphological and molecular data, Zootaxa 3683 (2), pp. 159-177 : 160-161

Nyx Harbach & Linton , gen. nov.

Type species: Nyx pholeocola Linton & Harbach , sp. nov.

Females. Medium-sized mosquitoes. Head: Eyes narrowly separated above antennae; vertex with large falcate scales and few broad scales laterally, ocular and interocular areas with smaller falcate scales, erect scales on occiput and back of vertex, interocular setae present; antenna longer than proboscis; maxillary palpus about 0.2 length of proboscis, with 3 normally developed palpomeres and a minute vestigial fourth palpomere. Thorax: Scutum with pattern of narrow pale and dark scales; acrostichal and dorsocentral setae present; scutellum with very narrow scales; paratergite narrow, without scales or setae; antepronotum with scales, postpronotum with few narrow scales; postspiracular setae and scales present. Wing: Remigium without setae; alula with broad scales on margin. Legs: Tarsi dark-scaled; both ungues of fore- and midlegs toothed, hindungues slightly smaller, apparently without teeth. Abdomen: Tergum I nearly completely covered with scales and setae, laterotergite with scales. Genitalia: Segment VIII retracted into segment VII; cercus relatively long, more than twice length of postgenital lobe; insula without setae; 3 spermathecal capsules.

Males. Essentially as the females. Head: Antenna about 0.75 length of proboscis, flagellar whorls long, dense, directed dorsally and ventrally, flagellomeres 12 and 13 elongate; maxillary palpus short, 0.4 length of proboscis, comprised of 4 palpomeres, fourth vestigial. Legs: Ungues of fore- and midlegs enlarged, anterior and posterior unguis of each pair with a tooth. Genitalia: Tergum IX lobes poorly developed, separated, with rows of setae; sternum IX with 1–3 medial setae; gonocoxite elongate, with lateral scales; gonostylus long, slender at base, distally flattened, expanded and highly setose; claspette small, tapered to acute apex with a few setae; aedeagus comprised of 2 tergally bent lateral plates, each plate with apical teeth; proctiger strongly developed, paraproct with sharp caudal spine, cercal setae absent.

Pupae. Cephalothorax: Seta 7-CT longer than seta 6-CT. Abdomen: Seta 3-III long, single; seta 6-III single, seta 6-VII small, posterior to seta 9; seta 9-IV–VI posterior to seta 8, seta 9-VII single, stout; paddle oval, external and internal margins smooth.

Larvae, fourth-instars. Head: Seta 4-C short, with 3 or 4 branches; setae 5,6,8,13-C single; seta 14-C longer than seta 15-C, single or double; cervical sclerite present. Thorax: Seta 1-P well developed, longer than seta 2-P; setae 1,3-P usually double (1,2); seta 5-P double; seta 5-T small, single. Abdomen: Seta 11-I large, 2,3-branched; seta 2-I,II large, 2,3-branched, inserted anterolateral to seta 1, seta 2-III–VI relatively small, single or double, inserted anterior to seta 1; seta 5-II–VII small, usually single; seta 7-II single, about half length of seta 6-II; seta 9- III–VI inserted near and anterior to seta 7; seta 10-II–V inserted lateral to setae 11,12; seta 13-III–V single. Segment VIII: Comb scales spine-like, in single row. Siphon: Acus present, detached; seta 1-S 2,3-branched, inserted distal to pecten; distal 1 or 2 pecten spines usually slightly more widely spaced. Segment X: Saddle incomplete, relatively large, extending below lateral midline, acus not developed, posterior margin with spine-like spicules; seta 1-X single, shorter than saddle; seta 2-X with multiple branches; seta 3-X single; ventral brush (seta 4-X) with 4 or 4.5 pairs of setae on grid (with only transverse bars) and 1 precratal seta.

Eggs. Unknown.

Etymology. Nyx is the Greek goddess of the night – a shadowy figure who stood at or near the beginning of creation and gave birth to a number of personified gods. Her sparse appearances in mythology reveal her as a goddess of exceptional power and beauty. Nyx was rarely and only glimpsed in the shadows of the world, which prompted the generic name proposed here. The two-letter abbreviation Nx. is recommended for this genus.

Systematics. The generic status and phylogenetic relationships of Nyx were assessed objectively by including character data for Nyx in the data set of Reinert et al. (2009). The characters used in the analyses and their states observed in Nyx are listed in the Appendix. Analyses using implied weights and values of K ranging from 5 to 17 each yielded a single most parsimonious (fittest) cladogram (MPC). With the most extreme weighting functions, K = 5 and 6, Nyx was placed as the sister group to Isoaedes, though the placement of this pair with other genera was quite different in the two MPCs. For K = 7–13, the pattern of relationships among the genera of the Stegomyia - group (the clade comprising genera Skusea to Stegomyia ) was consistently recovered and identical to that shown in figure 1 of Reinert et al. (2009), with the addition of Nyx , which was placed as a separate branch of the main stem between Isoaedes and Borichinda ( Fig. 1 ). The branching pattern at the base of the Stegomyia -group was thus: ( Skusea ( Indusius, Cancraedes )) ( Fredwardsius (Isoaedes ( Nyx ( Borichinda (( Diceromyia , Ayurakitia ) (Dendroskusea, remainder of the Stegomyia -group)))))). With K = 14 and 15, Isoaedes, Nyx and Borichinda formed a clade with the first two as sister taxa. The weakest weighting with K = 16 and 17 showed a similar but inverted pattern to that for K = 7–13: (Dendroskusea ( Diceromyia , Ayurakitia )) ( Borichinda ( Nyx (Isoaedes ( Fredwardsius (( Skusea ( Indusius, Cancraedes )), remainder of the Stegomyia -group))))). Reinert et al. (2009) found a similar “plateau of stability” between K = 7 and K = 10, and restricted their discussion to a consideration of the MPC found with K = 9. As we found a similar pattern, although now extended to K = 13, and for ease of comparison, we also restrict subsequent discussion to the MPC found using K = 9.

The branch supporting Isoaedes as sister to the rest of the Stegomyia -group is supported by 15 unambiguously optimized but homoplastic characters (33: 0, 54: 0, 98: 1, 101: 1, 158: 2, 188: 1, 198: 0, 226: 0, 240: 0, 256: 0, 261: 0, 262: 1, 266: 1, 273: 0, 326:0), which include nine (boldface) of 10 that supported the same branch in the study of Reinert et al. (2009). The branch uniting Nyx with the remainder of the Stegomyia -group to the exclusion of Isoaedes is supported by seven unambiguously optimized but homoplastic characters (7:0, 24:1, 34:1, 63:1, 92:1, 290:1, 317:1), and the branch supporting the clade comprising Borichinda and the rest of the Stegomyia -group to the exclusion of Isoaedes and Nyx is supported by 10 unambiguously optimized but homoplastic characters (40: 1, 52: 2, 55: 2, 58: 1, 64: 1, 67: 1, 110: 1, 232: 1, 255: 0, 328: 1). The emboldened characters in these two lists are those that supported the clade comprising Borichinda and the rest of the Stegomyia -group to the exclusion of Isoaedes in the study of Reinert et al. (2009). Thus, six of the original 13 characters that support this clade in Reinert et al. (2009) are now placed on the branch below Nyx and five on the branch above Nyx . The inclusion of Nyx rendered the optimization of the remaining character, 53:1, ambiguous. In other words, the addition of Nyx has simply resulted in the slotting in of this genus on the original branch between Isoaedes and Borichinda and the almost equal division of the characters that supported this branch on either side of the node leading to Nyx . Nyx itself is on a branch supported by 12 unambiguously optimized but homoplastic characters: 36: 1, 37: 0, 65: 1, 143: 2, 157: 2, 159: 0, 161: 0, 182: 3, 221: 1, 282: 1, 304: 2 and 308: 1. These differences clearly support the recognition of Nyx as a new polythetically diagnosed genus of tribe Aedini .

Figures

FIGURE 1. Placement of Nyx in the phylogeny of tribe Aedini when character data for Nx. pholeocola (Appendix) are added to the data set of Reinert et al. (2009) and analyzed using implied weighting and a concavity constant (K) of 9. Supporting characters are indicated on the branches. All are homoplastic, so Nyx, like most generic-level taxa of Aedini, is a polythetic genus that is diagnosed by a unique combination of characters.