Culicoides (Monoculicoides)

Shults, Phillip & Borkent, Art, 2018, Pupae of the Nearctic species of Culicoides Latreille subgenus Monoculicoides Khalaf (Diptera: Ceratopogonidae), Zootaxa 4504 (4), pp. 451-472 : 453-458

Subgenus Culicoides (Monoculicoides)

Diagnosis. The only group of species of Nearctic Culicoides with the following combination of pupal characters: Dorsal apotome without a dorsomedial tubercle, with dark banding on the apex of the pedicel and the base of the respiratory organ ( Fig. 1 ); respiratory organ elongate and slender, with a dark apex; midlength portion bearing scales ( Fig. 2 A–B), and 2–5 subbasal pores arranged along its length ( Fig. 2 A–B); shagreen present on the anterior and posterior margins of the abdominal segments with varying amounts of shagreen laterally ( Figs 6 A–B & 7A– B); and terminal processes extending posterolaterally and with a dark apex ( Fig. 8 A–B).

Description. Male. Total length = 2.05–3.70 mm. Light to medium brown coloration throughout ( Fig. 1 ). Head: Dorsal apotome (DA) with or without spicules, without dorsomedial tubercle, dorsal margin rounded, lateral margins with distinct points ( Figs 3 A–D & 4A–C), DA length (DAL) = 0.26–0.37 mm; DA width (DAW) = 0.17– 0.22 mm; DAW/DAL= 0.56–0.75. DA–1–H medium long, thick seta on well–developed tubercle, DA–2–H dorsal to tubercle base. Dorsolateral cephalic sclerite with one long, one short seta. Palpus extending posteriorly to posterolateral margin of labium, CL–1–H about twice length of CL–2–H. Thorax: Cephalothorax length = 0.96– 1.60 mm. Pedicel of respiratory organ short with dark banding at apex ( Fig. 1 ). Respiratory organ (RO) elongate, slender, apex dark brown, mid-length portion with scales, without annulations, with short membranous base, medium brown coloration on posterior margin, with pores closely abutting in single row at apex, 2–5 subbasal pores ( Fig. 2 A–B), RO length = 0.27–0.45 mm; RO width = 0.03–0.06 mm; ROW/ROL = 0.08–0.15, tracheal tube with reticulations. Anterolateral sensilla (one long, one short seta) on well–developed tubercle. Mesonotum with small bumps anterior to D–5–T, smooth posteriorly, D–1–T, D–2–T short, stout, each on rounded tubercle, D–3–T posterior to small rounded tubercle bearing long, slender D–4–T, D–5–T short or long, on small rounded tubercle, D–1–T, D–2–T, D–5–T in longitudinal row ( Fig. 5 A–B). Wing with apical tubercle; halter apex slightly separated from hind leg. Metathorax completely separated medially, with long, thin M–1–T near anterior margin, M–2–T, M–3–T more posterior. Abdomen: Tergites 2–7 each with darker pigmentation as medial group of

three patches, with anterolateral pair, sternites 3–7 each with two medial patches, with anterolateral pair ( Figs 1 , 6 A–B, & 7A–B). Distribution of shagreen of abdominal segments variable, though never excessive. Tergite 1 with long D– 3–I, short D– 2–I, D– 7–I anterior, campaniform D– 4–I, short D– 8–I, long, thin D– 9–I on short tubercle posteriorly, L– 2–I, L– 3–I short separated medially by long, thin L– 1–I. Tergite 2 without elongate tubercles, minute L– 2–II, L– 4–II separated medially by long, thin L– 3–II on anterolateral margin. Chaetotaxy of tergite 2, 3, 5–7 similar to that of tergite 4. Tergite 4 with short D– 2–IV on short tubercle, thin D– 3–IV on elongate, pointed tubercle, D– 5–IV, D– 4–IV, D– 7–IV, D– 8–IV, D– 9–IV in transverse row, arranged medially to laterally, minute D– 5–IV on slightly formed tubercle, D– 4–IV on small tubercle, D– 7–IV on small rounded tubercle, D– 8–IV, D– 9–IV each long on pointed tubercle, D– 8–IV seta thicker than D– 9–IV ( Fig. 7 A–B); lateral tubercles with elongate, slender apices, L– 1–IV thick seta on bifurcate tubercle, L– 2–IV, L– 4–IV thick setae, each on elongate bifurcate tubercle, separated by thin L– 3–IV on elongate bifurcate tubercle ( Figs 6 A–B & 7A–B); sternite 4 with minute V– 5–IV on small rounded tubercle, V– 6–IV thin on pointed tubercle, small V– 7–IV on pointed tubercle, ventral setae in transverse row, shagreen along anterior margins ( Fig. 6 A–B). Segment 8 chaetotaxy with seven sensilla: D– 8– VIII, D– 9–VIII, L– 2–VIII, L– 3–VIII, L– 4–VIII, V– 6–VIII, V–7 –VIII. Segment 9 with genital lobes extending to posterior margin, terminal process projecting posterodorsolaterally to laterally, tapered to pointed, dark apex ( Fig. 8 A–B).

Female. Similar to male other than sexual differences on segment 9 and the following: total length = 1.81–3.94 mm, DA length = 0.23–0.34 mm, DA width = 0.18–0.24 mm, DAW/DAL = 0.64–0.85, Cephalothorax length = 0.96–1.55 mm, Ro Length = 0.21–0.43 Mm, Ro Width = 0.03–0.06 Mm, Row/rol = 0.08–0.16. Taxonomic discussion. Comparison with the pupae of other species of C. ( Monoculicoides ) outside of the Nearctic Region was difficult due to limited material or because they remain undescribed. Of these species, we examined pupae of C. helveticus Callot , C. longicollis Glukhova , C. puncticollis (Becker) , and C. nubeculosus (Meigen) , and these were found to be consistent with our diagnosis for C. ( Monoculicoides ). Additionally we observed clear morphological differences between these species and the seven Nearctic species treated herein. Though this subgenus includes 23 species, only 13 have pupal descriptions, and we examined the pupae of ten of those species. The species of C. ( Monoculicoides ) with previously described pupae not examined here were those of C. cornutus de Meillon (Afrotropical) , C. homotomus Kieffer (Oriental) , and C. parroti Kieffer (Palearctic) . Although descriptions of these species include fewer pupal characters than the current study, we found no contradictory information to either the diagnosis or description here.

Of the 12 other subgenera of Culicoides that occur in North America, we have tested our subgeneric diagnosis against all of them. We re-examined Nearctic pupal exuviae from nine subgenera and compared literature descriptions of two subgenera (C. (Avaritia) and C. (Drymodesmyia )). We also tested our diagnosis against previously described pupae of an array of species groups and those considered miscellaneous ( Borkent 2016) as listed by Borkent (2014: Table 2), for some based only on descriptions of species outside the Nearctic Region.

This is the first diagnosis of the pupa of any subgenus within Culicoides other than that of C. (Selfia) by Atchley (1970) but which included errors (see below).

Figures

FIGURE 1. Habitus of the pupae of Culicoides occidentalis (left) and C. riethi (right) in dorsal view.

FIGURE 2. Respiratory organs, in lateral view. (A) Culicoides shemanchuki. (B) C. occidentalis.

FIGURE 3. Female, dorsal apotomes, in anterior view. (A) Culicoides occidentalis. (B) C. riethi. (C) C. sonorensis. (D) C. variipennis.

FIGURE 5. Thoracic dorsal setae, left side, dorsal view. (A) Culicoides shemanchuki. (B). C. occidentalis.

FIGURE 6. Male, lateral and ventral tubercles of abdominal segments 4, in dorsal view (A) Culicoides occidentalis. (B) C. riethi.

FIGURE 7. Male, lateral and dorsal tubercles of abdominal segments 4, in dorsal view (A) Culicoides sonorensis. (B) C. variipennis.

FIGURE 8. Female abdominal segments 8–9, in dorsal view. (A) Culicoides riethi. (B) C. occidentalis.