Culicoides debilipalpis Lutz

Ronderos, María M., Cazorla, Carla G. & Spinelli, Gustavo R., 2010, The immature stages of the biting midge Culicoides debilipalpis Lutz (Diptera: Ceratopogonidae), Zootaxa 2716, pp. 42-52 : 43-49

Culicoides debilipalpis Lutz

( Figs. 1–31 )

Culicoides debilipalpis Lutz, 1913: 60 (female; Brazil); Macfie, 1937: 7 (female; redescrip.; Trinidad); Floch & Abonnenc, 1942: 3 ( Guyane); Barbosa, 1952: 12 ( Argentina, Brazil); Forattini, 1957: 383 (in part.; redescrip.; distrib.); Wirth & Blanton, 1959: 442 (redescrip.; Panama); Franca Rodriguez, 1963: 67 ( Uruguay); Messersmith, 1964: 339 (Virginia; breeding site); Smith & Varnell, 1967: 520 (Florida; tree holes); Wirth & Blanton, 1971a: 34 (redescrip.; distrib.); Wirth & Blanton, 1971b: 75 ( khalafi as syn.; notes); Blanton & Wirth, 1979: 78 (redescrip.; distrib.); Vitale et al., 1981: 149 (notes; Panama); Spinelli & Ronderos 1997: 304 (revalidation); Borkent & Spinelli, 2000: 32 (in Neotropical catalog); Ronderos et al., 2003a: 22 (Yacyretá dam lake area); Spinelli et al., 2005: 141 (in key; Argentina); Trindade & Gorayeb, 2005: 67 (Pará, Brazil); Borkent & Spinelli, 2007: 66 (in Neotropical catalog); Borkent & Grogan, 2009: 14 (in Nearctic catalog); Borkent, 2009: 80 (in online World catalog).

Culicoides ichesi Ronderos & Spinelli, 1995: 77 (female; Argentina, Paraguay, Uruguay); Ronderos & Spinelli, 1998: 81 (in key; Yacyretá dam lake area).

Culicoides khalafi Beck, 1957: 104 (male, female; Florida; fig.).

Culicoides lahillei: Spinelli & Wirth, 1986: 62 (misident., in part., syn. debilipalpis ); Wirth et al., 1988: 48 (in Atlas , wing photo.); Spinelli et al., 1989: 735 (in list); Spinelli & Ronderos, 1991: 91 (Salto Grande dam lake area); Spinelli & Martinez, 1991: 176 (in key; Uruguay); Waller et al., 1990: 352 (redescrip; Guyana);? Lamberson et al., 1992: 117 (descrip. pupa; Georgia and Missouri, USA); Borkent & Wirth, 1997: 72 (in catalog; syn. debilipalpis ).

Fourth instar larva ( Figs. 1–14 ). For measurements and ratios of head capsule and caudal segment with SEM see Table 1. Larvae length 2.29 mm (SEM). Small larva. Head capsule ( Figs. 1–2 , 8, 14 ) yellowish, moderately elongate, apex slightly bent ventrally, HL 0.14–0.17 (0.155, n=11) mm, HW 0.09–0.14 (0.114, n=11) mm, HR 0.56–0.87 (0.738, n=11), SGW 0.096–0.10 (0.098, n=3), SGR 1.20–1.26 (1.24, n= 3). All setae simple, moderately thin, medium-sized to elongate, chaetotaxy as in Figs. 1–2 . Antenna short. Labrum ( Figs. 1, 3 ) as long as its greatest, basal width, with pair of anterolateral sensilla styloconica ( Fig. 5 ); palatum ( Figs. 3, 5 ) with 3 pairs of closely-spaced sensilla trichoidea ( Fig. 5 ); messors ( Fig. 5 ) small, thin, gently sclerotized, curved; well developed scopae ( Figs. 3–4 ). Maxilla ( Figs. 2–5 ) with short papillae; maxillary palpus ( Fig. 3–5 ) short, cylindrical, with 4 subapical papillae, two long, other two short, triangular-shaped lateral lobe; galeolacinia with long seta ( Figs. 4–5 ). Mandible ( Figs. 1–5 ) medium length, hooked, curved, with broad base, two elongate, small pointed teeth, inner tooth smaller, with medium-sized setae on basal portion near hypocondyle, one insertion of seta on ectal margin ( Fig. 3 ); ML 0.06 mm, MW 0.03 mm. Hypostoma ( Figs. 2–3, 5 , 8 ) with quadrangular, mesal, smooth elevation, lateral margin serrate. Labium small. Epipharynx ( Figs. 8, 10–14 ) poorly massive, with 2 ventral combs superimposed, dorsal comb sclerites short, with 22–24 small rounded teeth on posterior edge; lateral arms membranous with lateral curtains, LAW 0.051–0.055 (0.054, n=3) mm, DCW 0.011–0.018 (0.016, n=3). Hypopharynx ( Figs. 8–9, 14 ) elongate, thin, moderately sclerotized, arms without fringe or posterior comb. Thoracic pigmentation uniformly pale, with notorious long setae. Abdominal segments whitish. Caudal segment ( Figs. 6–7 ) with 6 pairs of setae, four of these long, stout, pale brown, other two thin; CSL 0.305–0.309 (0.306, n=3) mm, CSW 0.129–0.156 (0.146, n=3) mm, CSR 0.38–0.51 (0.462, n=3), OL 0.150–0.204 (0.171, n= 7) mm, OD 0.022–0.026 (0.023, n=6) mm.

Instars I–III. Similar to fourth instar, but with differences in size and some proportions. For measurements and ratios with SEM see Table 1.

measurements are in millimeters.

Larval instar

I II III IV

Head Capsule HL 0.0916 0.0973 0.117 0.134 HW 0.0809 0.0812 0.0875 0.0915 HR 1.13 1.19 1.33 1.46 SGW 0.0565 0.0556 0.0490 0.0451 SGR 1.43 1.46 1.78 2.02

Caudal Segment CSL --- --- 0.249 0.361 CSW --- --- 0.101 0.156 CSR --- --- 2.46 2.31 OL --- --- --- 0.193 OD --- --- 0.06 0.078

Female pupa ( Figs. 15–31 ). Exuviae pale yellowish brown. Length of cephalothorax 0.792–1.025 (0.908, n= 6) mm, its width 0.466–0.605 (0.566, n= 6) mm. Operculum ( Figs. 15–16, 20 , 22) slightly wider than long, distal margin nearly straight; disc surface covered by stout rounded spinules; anteromarginal tubercle (am) welldeveloped, 0.0329 mm (SEM) ( Figs. 15–16, 20 , 22), base rounded, wide, with one long, stout, pointed seta inserted in a conical-shaped area, 0.0852 mm (SEM); basal sensillum present; posterior margin slightly convex, smooth except for few small rounded spinules between anteromarginal tubercles; OL 0.122–0.186 (0.171, n=6) mm; OW 0.022–0.026 (0.023, n=7) mm; OW/OL 1.04–1.31 (1.18, n=4). Respiratory horn ( Figs. 15–17 , 29 ) medium-sized, slender, yellowish, distal half dark brown, large scale-like spines; 7–8 apical spiracles, 2–3 laterobasal ones; pedicel stout, P 0.033–0.04 (0.037, n=4) mm; RH 0.17–0.19 (0.18, n=5) mm; P/RH 0.132, 0.19–0.21 (0.20, n=4). Cephalothoracic tubercles as follows: anterodorsal tubercle (ad) prominent, with large, pointed setae ( Figs. 15–16 ); dorsolateral tubercle (dl) ( Figs. 15–17, 19–20 ) small, blunt, with 2 setae, one long, thin, other minute; dorsal tubercles (d): i with minute seta, ii with medium-sized, stout seta; iii with long seta; iv with very long, thin seta, v small, minute seta ( Figs. 16, 21 ). Two ventrolateral (vl) long, thin setae ( Fig. 18 ); 2 ventromedial (vm), mediumsized setae, one stouter ( Fig. 18 ). Abdominal segments with smooth integument, with scarce spicules spread on anterior and posterior portions; each segment with small pigmented anterolateral spiracle (sp). First abdominal segment ( Fig. 30 ) with setae as follows: 2 anteromesal thin setae, one long, other medium-sized; 2 posterior setae, mesal one very long, thin, other minute. Fourth segment (Figs. 23–25, 31) with all tubercles with small base: 2 dorsal anterosubmarginal tubercles (dasm), i–ii short setae, i thiner than ii; 5 dorsal posteromarginal tubercles (dpm), i–ii short seta, iii without seta, iv–v minute setae; 3 lateral posteromarginal tubercles (lpm), i, iii spur-like, pointed setae, ii very long, thin seta; one lateral anterosubmarginal tubercle (lasm) spur-like seta; 3 ventral posteromarginal tubercles (vpm), i minute seta, ii long, thin seta, iii short, stout seta. Caudal segment (Fig. 26) approximately 1.25 times as long as greatest width, length 0.18–0.22 (0.201, n= 7) mm, width 0.10–0.19 (0.146, n= 7) mm; posteriorly directed spicules restricted to narrow anterior band, not connected to central inverted V-shaped patch of spicules; mesal spicules patch not extending to posterolateral processes, these moderately elongated, subparallel with pointed, dark tips; ventral surface of posterolateral processes with spicules present on each side of midline. Male caudal segment (Figs. 27–28) similar to female.

Material examined. All the specimens collected as larvae, reared in laboratory. Argentina, Entre Ríos prov., Ibicuy, from tree – holes of Salix sp., 7-XI-2006, R. Campos-C. Cazorla, 2 larval exuviae (instar IV), 11 larvae (instar IV), 5 female pupal exuviae, 3 pupae, 2 adult females, 1 adult male.

FIGURE 22–28. Culicoides debilipalpis , pupa. Figs. 22–26: female (digital camera). Figs. 27–28: male (SEM). Fig. 22: operculum. Fig. 23: 4th abdominal segment (lateroventral view). Fig. 24: 4th abdominal segment (dorsal and ventral views). Fig. 25: 4th abdominal segment (dorsal view). Figs. 26–27: caudal segment (ventral view). Fig. 28: caudal segment (anteroventral view).

Material examined by SEM: same data, 6 larvae (1 instar I, 1 instar II, 1 instar III, 3 instar IV), 6 pupae. Distribution. Widespread from USA (Maryland, Kentucky, Nebraska south to Lousiana and Florida), Guatemala and Belize to Argentina (Jujuy, Misiones, Corrientes, Entre Ríos, Buenos Aires provinces).

Bionomics. The freshly collected larva is basically salmon colored. When kept in the laboratory, it losses some of this pigmentation, probably as a result of the adapted diet. The larva shows a good adaptation for swimming and typical active movement. They are positively phototrophic and their activity increases when they are observed under light. Observations during the conduct of this work indicate that this species feeds on microorganisms carried in the standing water and organic matter of their natural environment.

The life cycle of Culicoides debilipalpis from larva to adult lasted approximately 31 days in the laboratory. The pupa movement is slow, undulating the last seven abdominal segments, which might be used to keep floating.

Figures

FIGURE 1 – 7. Culicoides debilipalpis, larva (SEM). Fig. 1: head capsule, chaetotaxy (dorsolateral view). Fig. 2: head capsule, chaetotaxy (ventrolateral view). Fig. 3: head capsule (anterolateral view). Fig. 4: maxilla (lateral view). Fig. 5: head capsule (anteroventral view). Fig. 6: caudal segment, chaetotaxy (dorsal view). Fig. 7: caudal segment, insertion of setae “ o ”.

FIGURE 8 – 14. Culicoides debilipalpi s, larva (digital camera). Fig. 8: head capsule, epipharynx (ventral view). Fig. 9: hypopharynx. Fig. 10: detail epipharynx comb (ventral view). Fig. 11: detail epipharynx comb (dorsal view). Fig. 12: epipharynx, detail combs 3 and 4 and curtain. Fig. 13: epipharynx, detail lateral arm and curtain. Fig. 14: head capsule (lateral view).

FIGURE 15 – 21. Culicoides debilipalpis, pupa (SEM). Fig. 15: cephalothorax (ventral view). Fig. 16: cephalothorax (anterodorsal view). Fig. 17: respiratory horn. Fig. 18: ventromedian and ventrolateral setae. Fig. 19: dorsolateral tubercle. Fig. 20: cephalothorax (anterior view). Fig. 21: dorsal tubercles (lateral view).

FIGURE 29 – 31. Culicoides debilipalpis, pupa. Fig. 29: respiratory horn. Fig. 30: first abdominal segment, detail tubercles. Fig. 31: fourth abdominal segment, detail tubercles.