Hydrosmittia falsicostata, Ferrington Jr & Saether, 2011

Ferrington Jr, Leonard C. & Saether, Ole A., 2011, A revision of the genera Pseudosmittia Edwards, 1932, Allocladius Kieffer, 1913, and Hydrosmittia gen. n. (Diptera: Chironomidae, Orthocladiinae) 2849, Zootaxa 2849 (1), pp. 1-314 : 135-138

Hydrosmittia falsicostata sp. n.

( Figs. 48 , 49 )

Type material: Holotype: Mature male pupa, KENYA: Mt. Kenya, Liki stream, 13,200' 21.xii.1980, P. S. Cranston, BM 1981–79 ( BMNH) .— Paratypes: 4 males, 2 larvae as holotype ( BMNH); Mt. Kenya , sweep net, 4,350 meters , 8 males i.1976, W. Wülker ( ZMBN, MU) .

Diagnostic characters: The male imago differs from other Hydrosmittia except H. ruttneri and H. kisotriangulata in lacking inner verticals. The larger size, wing length of 2.1–2.7 mm, as well as the darker wing with a distinct false vein continuing from the apex of R 4+5 will separate the species from H. ruttneri . From the equally large H. kisotriangulata it can be separated by having an AR of 0.9–1.1 compared with about 2.0 in H. kisotriangulata and by having less strong virgal spines. The pupa is characterized by lacking frontal setae and anal macrosetae as in H. ruttneri , but differs from that species by having tergal conjunctives II/III and VII/VIII each with about 30–37 spinules. The larva has a mandible with 3 inner teeth and 10 claws on the posterior parapods. It differs from H. ruttneri in the shorter posterior parapods (98 µm) and in having 3 weak anal setae.

Etymology: From the Latin falsus, false, and costatus, having lines or ribs, referring to the false extension of the costa.

Male imago (n = 10–12, except when otherwise stated)

Total length 3.16–4.17, 3.65 mm. Wing length 2.13–2.67, 2.50 mm (14). Total length/wing length 1.43–1.56, 1.50. Wing length/length of profemur 3.32–3.57, 3.42. Coloration brownish black, wings tinged with grayish brown.

Head ( Fig. 48 B ). AR 0.91–1.11, 1.01 (15). Terminal flagellomere 459–585, 532 µm (15) long, pointed. Temporal setae 3–7, 6 (16), consisting only of outer verticals. Clypeus with 5–7, 6 setae. Tentorium 137–174, 159 µm long, 29–59, 40 µm wide. Cibarial pump and stipes as in Fig. 48 D . Stipes 144–165, 158 µm long, 34–57, 45 µm wide. Palpomere lengths (in µm): 27–42, 35; 48–64, 56; 98–160, 136; 110–146, 120; 169–219, 195. Third palpomere ( Fig. 48 C ) with 2–3, 2 lanceolate sensilla clavata.

Thorax. Antepronotal with well developed median lobes, with 1–3, 2 weak lateral setae. Dorsocentrals 5–12, 9 (14), acrostichals 2 (15), prealars 3–4, 3, supraalar seta absent. Scutellum with 6–9, 7 setae.

Wing ( Fig. 48 A ). VR 1.16–1.23, 1.21. Anal lobe slightly projecting. Costal extension usually obscured by false vein, only measurable in 3 specimens, 23–40 µm long, length of false vein plus costal extension 160–240, 209 µm. R 4+5 ending slightly distal to apex of M 3+4; Cu 1 sinuate. Brachiolum with 1 seta, R with 4–13, 7 setae, R 1 with 0–2, 0 setae, other veins bare.

Legs. Spur of front tibia 39–49, 44 µm long, spurs of middle tibia 21–29, 25 µm and 16–25, 20 µm long, of hind tibia 53–66, 58 µm and 18–27, 21 µm long. Width at apex of front tibia 30–41, 36 µm, of middle tibia 30–41, 36 µm, of hind tibia 39–57, 49 µm. Comb of 12–16, 14 setae, shortest seta 23–32, 26 µm long, longest seta 41–55, 49 µm long. Lengths and proportions of legs as in Table 28.

Hypopygium ( Fig. 48 F ). Anal point 5–43, 21 µm long, apex free of microtrichia; tergite IX with 10–18, 14 setae; laterosternite IX with 4–5, 5 setae. Phallapodeme 91–107, 96 µm long; transverse sternapodeme 69–83, 76 µm long, oral projections well developed. Virga ( Fig. 48 E ) consisting of 9–14 µm (2) long weak median plate and about 18–30, 24 lateral spinules. Gonocoxite 216–251, 233 µm long; inferior volsella well developed, reaching to 0.57–0.64, 0.60 gonocoxite length; accessory lobe well developed and reaching to 0.69–0.81, 0.75 gonocoxite length. Gonostylus 91– 117, 107 µm long, without distinct heel; megaseta 10–14, 11 µm long. HR 2.15–2.37, 2.18; HV 3.41–3.56, 3.41.

Pupa (n = 1)

Total length about 3.9 mm. Exuviae tinged with grayish brown, including anal segment.

Cephalothorax. Frontal seta absent. Longer precorneal, median antepronotal, and dorsal lateral antepronotals 90– 115 µm long; shorter precorneal and dorsocentrals 50–70 µm long. Distance between Dc 1 and Dc 2 89 µm; between Dc 2 and Dc 3 5 µm; between Dc 3 and Dc 4 7 µm.

Abdomen ( Fig. 49 A ). Tergite I with strong anterior shagreen and weak posterolateral shagreen; T II–VIII with shagreen evenly over whole segments; T IX with shagreen spinules covering most of segment. Sternite I with fine posterolateral shagreen; SII–III apparently with lateral and posterior shagreen; S IV–VIII with relatively coarse shagreen covering most of segment; S IX with anterolateral shagreen. Tergal conjunctive II/III with 37 spinules; III/IV with 43; IV/V with 52; V/VI with 61; VI/VII with 51; VII–VIII with 30 spinules. Sternal conjunctives III/IV with 2 spinules; IV/V with 57; V/VI with 66; VI/VII with 52; VII/VIII with 36; VIII/IX with 4 spinules. Anal segment without setae. Male genital sac with wide caudolateral papilla.

Fourth instar larva

All measurements and ratios within the variation of H. ruttneri with the following exceptions: Antennal blade ( Fig. 49 B ) 10–13.5 µm (2) long; posterior parapods 98 µm (1) long.

Remarks

This species is very close to H. ruttneri and could perhaps be regarded as a darker and larger form of that species. The differing length of the posterior parapods of the larva is significant. However, this measurement needs to be checked when more larvae of H. falsicostata become available.

Distribution and ecology

The species is known only from Mt. Kenya, with the larva collected in Liki streams.

Figures

FIGURE 48. Hydrosmittia falsicostata sp. n., male. A—wing; B—head; C—third palpomere; D—cibarial pump and stipes; E—virga; F—hypopygium, left dorsal aspect, right ventral aspect.

FIGURE 49. Hydrosmittia falsicostata sp. n., immatures. A—female pupa, posterior tergites; B—larval antenna; C—premandible; D—mandible; E—labrum and epipharynx; F—mentum.