Onconeura semifimbriata (Saether) Saether, 2005

Andersen, Trond & Saether, Ole A., 2005, Onconeura, a new Neotropical orthoclad genus (Chironomidae, Orthocladiinae), Zootaxa 957, pp. 1-16 : 13-15

Onconeura semifimbriata (Saether) new combination

( Fig. 4 A–C)

Material examined. MEXICO: Nuevo León, Allende, Rio Ramos at Raices, 25°14.53'N 100°02.07'W, 20.ix.1998, 2 males, 5 pupal exuviae, net & driftnet, T. Andersen & A. Contreras­Ramos. In addition, the material mentioned in Saether (1981: 32) was re­examined.

Diagnostic characters. The male imago is separable from that of O. undecimata by having 12 flagellomeres, smaller size, and more pale coloration with distinctly ringed legs. Having a well­developed frontal seta, smaller hooklets on tergal conjunctives, and an anal lobe with 26–31 equal­sized taeniae in the fringe can distinguish the pupa. The larva has a mentum with a single median tooth and six pairs of lateral teeth ( Fig. 4 C).

Remarks. The type material was based on bleached, brittle, and teneral specimens. The coloration thus was not possible to observe, the number of sensilla chaeticae was overstated, and, as seen from the material of O. undecimata , the female coxosternapodeme had not reached full sclerotization. The two males from Mexico, which also are somewhat smaller, thus are described here.

Male imago (n = 2)

Total length 1.29–1.43 mm. Wing length 0.68–0.71 mm. Total length/wing length 1.90–2.01. Wing length/length of profemur 2.68–2.71. Thorax yellowish brown, with vittae, scutellum except central parts, postnotum, preepisternum, parts of anterior and median anepisternum II, and part of epimeron II blackish brown. Legs with dark spot on coxae, fore trochanter dark, femora dark apically, base of tibiae and apex of mid and hind tibiae dark, central parts of mid and hind tibiae and basal half of mid and hind metatarsi whitish.

Head. AR 0.17–0.28. With 12 flagellomeres, ultimate flagellomere 92–94 m long. Temporal setae 2, including 1 outer verticals and 1 postorbital. Clypeus with 8–10 setae. Tentorium 113–124 m long, 11–15 m wide. Stipes 83–94 m long, 19 m wide. Palpomere lengths (in m): 26, 26–30, 41–43, 64–68, 83–94.

Thorax. Antepronotum with 2 setae. Dorsocentrals 10–12, prealars 2–3, supraalar apparently absent. Scutellum with 4 setae.

Wing. VR 1.70–1.84. Clavus 19–26 µm wide, ending 240–255 µm from arculus, with 1–2 setae at apex.

Legs. Spur of front tibia 30–34 m long, spurs of middle tibia 23–26 and 11–13 m long, of hind tibia 34 and 19 m long. Width at apex of front tibia 23–24, of middle tibia 26 m, of hind tibia 30 m. Length (in m) and proportions of legs as in Table 3 .

Hypopygium ( Fig. 4 A–B). Tergite IX with 16–17 minute setae, laterosternite IX with 2 setae. Phallapodeme 43–45 m long, transverse sternapodeme 24–26 m long. Gonocoxite 105–107 m long, superior volsella 8 m wide, barely joined basally. Gonostylus 39–41 m long, megaseta 9 m long. HR 2.59–2.67, HV 3.29–3.48.

Ecology and distribution. The species is known from streams and rivers in St. Vincent, Costa Rica, Guatemala, and Mexico ( Spies & Reiss 1996).

Figures

FIGURE 4. Onconeura semifimbriata (Saether), (A – B) male imago from Mexico, (C) larva from St. Vincent. A. tergite IX and dorsal aspect of left gonocoxite and gonostylus; B. hypopygium with anal point and tergite IX removed, left dorsal aspect, right ventral aspect; C. mentum.

Tables

TABLE 3. Lengths (in m, as range) and proportions of legs of Onconeura semifimbriata (Saether), male (n = 2).

	fe	ti	ta1	ta2	ta3	ta4	ta5	LR	BV	SV	BR
p1	246–265	250–265	203–217	57–61	33–38	19	28	0.81–0.82	5.10	2.43–2.44	1.8–2.0
p2	302–312	293–312	189–203	85–90	38–47	19	38	0.65	4.49–4.61	3.07–3.15	1.6–1.8
p3	265–269	288–312	198–213	104	33–38	19	28	0.68–0.69	4.00–4.28	2.71–2.80	1.7–2.4