Culicoides (Wirthomyia) bottimeri Wirth

Culicoides (Wirthomyia) bottimeri Wirth

(Figs. 1–10)

Culicoides bottimeri Wirth 1955: 356 (female, male; Texas; figs. female palpus, male parameres, genitalia)

Culicoides (Oecacta) bottimeri: Wirth 1965: 129 (in catalog; distribution) Culicoides (Wirthomyia) bottimeri: Vargas 1973:112 (in new subgenus); Wirth et al. 1985: 34 (female wing photo; distribution).

Culicoides multidentatus Atchley & Wirth 1975: 1421 (female; Arizona, California, New Mexico; figs. eyes, antenna, palpus, spermathecae); Wirth et al. 1985: 38 (female wing photo; distribution). New Synonym

Diagnosis: A species of Culicoides of the subgenus Wirthomyia distinguished from all other North American species in the genus by the following combination of characters: Female: antennal flagellum with sensilla coeloconica on flagellomeres 1–8, distal 5 flagellomeres considerably longer than proximal 8, antennal ratio 0.91–1.04; 3rd palpal segment moderately to greatly swollen, bearing broad, round shallow sensory pit, palpal ratio 1.79–2.42; mandible with 9–12 tiny teeth; lacinia with 25–37 teeth; thorax including femora and tibiae brown, tarsi slightly lighter in color, fore tibia with faint pale basal band; wing unpatterned, bearing numerous macrotrichia on wing membrane and veins, wing length 0.87–1.18 mm, costal ratio 0.46–0.55; sternite 8 with distinctive M­shaped sclerotization bearing pair of widely spaced setae; 2 ovoid spermathecae with short necks plus small rudimentary spermatheca, sclerotized ring absent. Male: slightly smaller, similar to female; genitalia with large, elongate, conical, widely spaced apicolateral processes; aedeagus with slender basal arms, deep basal arch and short, truncate apical projection; parameres separate, with small, ventral, molar­like knobs, distal portion slender, elongate, saber­shaped, bearing numerous serrations on inner and outer margins.

Female. Head (Fig. 7): Brown. Eyes bare, contiguous to narrowly separated by 0.2–0.6X the diameter of ommatidium. Sensilla coeloconica on flagellomeres 1–8, usually in groups of 3 except in groups of 5 on flagellomere 1 (occasionally in groups of 3 or 4), rarely single or double on flagellomeres 7 and 8; antennal ratio 0.98 (0.91–1.04, n = 27). Segment 3 of palpus 1.4X as long as segments 4+5 combined; moderately to greatly swollen; palpal ratio 2.11 (1.79–2.42, n = 28); sensory pit broad, round, not enlarged internally, about half as deep as width of opening. Proboscis short, proboscis/head ratio 0.6–0.7; mandible with 9–12 tiny teeth; lacinia with 25–37 large teeth. Thorax: Brown, without distinct pattern. Legs light brown, faint pale basal band on fore tibia; tarsi slightly paler; femoral­tibial joints dark; hind tibial comb with 5, rarely 6 spines, 1st and 2nd spines from spur subequal in length; hind tarsomere 1 lacking apical spines. Wing devoid of pattern; macrotrichia abundant over entire wing surface and veins except sparse near wing base and in basal portions of cells r3, m2, and anal cell; wing length 0.99 (0.87–1.18) mm, n = 33, breadth 0.47 (0.40–0.57) mm, n = 34; costal ratio 0.53 (0.46–0.55, n = 33). Halter pale, rarely infuscated proximally. Abdomen: Brown. Sternite 8 with distinct, dark brown, sclerotized M­shaped area (Fig. 1) bearing pair of large setae. Two ovoid, unequal­sized spermathecae (Figs. 2–4) with short to slightly elongated tapering necks, necks about 0.1X as long as spermathecae, plus small, ovoid, rudimentary spermatheca (Fig. 2) that is moderately well developed in some specimens (Figs. 3–4); sclerotized ring absent.

Male. Slightly smaller, similar to female, with the following notable sexual differences. Head (Fig. 8). Eyes contiguous. Antennal flagellum with sensilla coeloconica present on flagellomeres 1, 5–10, occasionally absent on 5, 9 or 10. Palpal segment 3 slightly longer than segments 4+5 combined, only slightly swollen, nearly cylindrical; palpal ratio 2.94 (2.38–3.60, n = 14); sensory pit small, round, 1.2X deeper than wide. Thorax: Femoral­tibial joints not darkened; hind tibial comb with 5 spines, 2nd from spur longest; hind tarsomeres lacking apical spines. Wing with macrotrichia on anteriodistal portion of membrane, sparse over remaining distal 2/3, absent on proximal 1/3; wing length 0.87 (0.76–1.03, n = 15) mm, breadth 0.33 (0.27–0.41, n = 14) mm; costal ratio 0.46 (0.43–0.50, n = 15). Halter pale, rarely infuscated. Genitalia (Figs. 9–10): Sternite 9 with broad, shallow caudomedian excavation, ventral membrane spiculate; tergite 9 long, tapering distally, without medial notch (Fig. 5) in most specimens, with small medial point (Fig. 6) in most specimens from Utah, apicolateral process triangular, elongate, apex pointed. Gonocoxite nearly straight, roots simple; dorsal root short, broad; ventral root long, sinuate, apices nearly touching but not obviously joined, without heel­like process. Gonostylus swollen basally, curved, gradually tapering on distal 0.8, tip narrowly pointed. Aedeagus with long slender, slightly recurved apically basal arms; basal arch, broad, deep, trapezoidal, extending about 0.8 of total length of aedeagus; distal median process small, slightly longer than broad, with small apicolateral points and small apical projection that is directed ventrally. Parameres separate, each half long, with small ventral molar­like knobs at base and sub­basally on proximal portion, abruptly bent on mid portion; distal portion heavily sclerotized, elongate, curved, saber­like, with row of 9–12 pairs of spicules along proximal 2/3 and 7–11 serrations along distal 1/3.

Distribution: California east to Texas and Utah (New State Record).

Specimens examined: Arizona: Cochise Co., Ramsey Canyon, Huachuca Mtns., July 1957, W. Brown (light), 1 female (Paratype of C. multidentatus, USNM); Yavapai Co., Oak Creek at Deer Pass Crossing, 11 May 1977, M. W. Sanderson, LT, 1 female (Paratype of C. multidentatus, USNM). California: Butte Co., Oroville, 6/15/01–9 /16/01, L. McClellan, UV Light (UCRC); Mendocino Co., Hopland, 15 June 1966, M. Knudsen, ex. Quail, 2 females, 27 June 1966, Murphy & Knudsen, ex. Quail trap, 1 female, 28 June 1966, F. K. Murphy, ex. Quail, 1 female, 21 Aug. 1966, F. K. Murphy, ex. Quail, 1 female (all are Paratypes of C. multidentatus, USNM); San Luis Obispo Co., Paso Robles, 25 June 1948, W. W. Wirth, 1 female (Paratype of C. multidentatus, USNM). New Mexico: Grant Co., Roberts Lake, 31 July 1965, W. R. Atchley, 1 female (Paratype of C. multidentatus, USNM). Texas: Kerr Co., Kerrville, July– 4 Aug. 1953, L. J. Bottimer, LT, 4 females, 2 males (Paratypes of C. bottimeri, USNM), 1 April 1955, W. W. Wirth, light trap, 1 female (WLG collection); Gillespie Co., Fredericksburg, VII 1967, Blanton & Borchers, light trap, 1 male (WLG collection). Utah: Grand Co., W. Moab, 19­VI­03, R. A. Phillips, CO2 trap, 1 female, 4 km SW Moab, 13­IX­00 / 15­VIII­01, R. A. Phillips, LT, 1 female, 2 males, 29­V­02 / 15­VIII­03, R. A. Phillips, UVLT, 3 females, 2 males, 7 km SE Moab, 26­ VI­01 / 11­X­03, R. A. Phillips, CO2 trap, 7 females, 2 males, 6 km SE Moab, 30­V­01, R. A. Phillips, CO2 trap, 1 female, 8 km SE Moab, 5­IX­02, R. A. Phillips, UVLT, 1 female (MMAD).

Taxonomic discussion: Our examination of recently collected specimens of C. bottimeri from Butte County, California, and Grand County, Utah, provide convincing evidence for relegating C. multidentatus to a junior objective synonym of C. bottimeri. In his original description of C. bottimeri, Wirth (1955) stated that the spermathecae have the “bases of the ducts not sclerotized”, but did not illustrate these structures. However, our examination of four female paratypes of C. bottimeri plus an additional female that was identified by W.W. Wirth as this species, all from the type­locality in Kerrville, Texas, revealed that their spermathecae have short tapering necks. These necks are particularly evident on the larger spermatheca of a paratype from Kerrville, Texas (Fig. 2), and are similar to those of C. multidentatus from Arizona (Fig. 3) and Utah (Fig. 4).

The Texas specimens of C. bottimeri have 27–30 lacinial teeth and 11 or 12 tiny mandibular teeth, both of which are within the range (25–35 lacinial and 9–12 mandibular teeth) for specimens identified as C. multidentatus from Texas and California and similar to the 33 (stand. dev. 2.878) lacinial and 9 (stand. dev. 1.862) mandibular teeth described for C. multidentatus by Atchley & Wirth (1975). The only character that we discovered that would distinguish the Texas females of C. bottimeri from the paratypes of C. multidentatus from California, was the greater number of sensilla coeloconica on their proximal 8 flagellomeres, which are usually in groups of 3 or 4 in C. bottimeri but range from 1 to 4 in C. multidentatus. However, we do not consider any of these minor differences to be of specific significance.

Males of C. bottimeri from Texas and California are virtually indistinguishable except for the reduced number of sensilla coeloconica on the proximal flagellomeres of the California males. The males from Utah differ from those from California and Texas by their slightly reduced sensillar pattern, and most Utah specimens possess a small medial point between the apicolateral processes (Fig. 6), from which they also differ from all California males. However, only 8 of the 9 slide­mounted males from Utah that we examined possess this medial point, an indication that this character is variable even within the Utah population.

In their wing atlas of the Nearctic species of Culicoides, Wirth et al. (1985) apparently did not assign C. multidentatus to the subgenus Wirthomyia, as they included it in a group of “miscellaneous unplaced species.” Because our study demonstrates that C. multidentatus is a junior synonym of C. bottimeri, we believe that both forms belong to the subgenus Wirthomyia. The only other North American species of Culicoides in the subgenus Wirthomyia, C. stilobezzioides Foote & Pratt (1954), has a boreal distribution, ranging from Newfoundland and Ontario, south to New York, west to Minnesota and Nebraska, and in the northwest from Alaska south to Washington. As in C. bottimeri, the wing of C. stilobezzioides is pale gray and lacks definitive spots (Foote & Pratt 1954, Jamnback 1965, Wirth et al. 1985). Females of C. stilobezzioides differ from those of C. bottimeri in being larger (female wing length 1.50–1.70 mm), having the wing macrotrichia shorter but more extensively distributed on the proximal portion of the wing, the costa longer (costal ratio 0.59–0.62), and the palpal pit deeper, being nearly as deep as the width of the pit opening. Males of C. stilobezzioides have only 3 or 4 long spicules on the subapices of the distal portions of their parameres, in contrast to the numerous spicules and serrations along the entire length of the distal portions of the parameres of C. bottimeri.

Bionomics: Numerous specimens of C. bottimeri were captured by light trap in both California and Utah from late May through early October. Published records for this species by Wirth (1955), Atchley & Wirth (1975), and Weinmann et al. (1979) indicate similar seasonal distributions. Figure 11 depicts seasonal activity of C. bottimeri during 2001–2003 in Grand County, Utah. Females had a relatively low capture rate, with carbon dioxide baited (but unlit) traps, when compared with most other species of Culicoides. Only 11 specimens were captured by carbon dioxide baited traps, whereas 104 individuals were captured by light traps, even though 70% of the trapping effort in Utah was with carbon dioxide alone. Some bird­feeding species of Culicoides, while common in light traps, may be poorly collected by CO2­baited suction traps (Mullens & Dada 1992). The ornithophilic feeding habits of females of C. bottimeri likely explain why CO2­baited traps yielded only about 10% of the females captured in Utah.