Culicoides (Avaritia) obsoletus (Meigen)

Phillips, Robert A., 2022, Culicoides Latreille and Leptoconops Skuse biting midges of the southwestern United States with emphasis on the Canyonlands of southeastern Utah (Diptera: Ceratopogonidae), Insecta Mundi 2022 (907), pp. 1-214 : 48-50

Culicoides (Avaritia) obsoletus (Meigen)

( Fig. 65 , 118 , 177)

Because C. obsoletus (Meigen) has been recognized as a species complex and because the conspecificity of the Palearctic with the Nearctic C. obsoletus is in question ( Meiswinkel et al. 2004), only the Nearctic and limited Palearctic data and references are presented. (However, Mathieu et al. [2020] has cast doubt on Holarctic C. obsoletus having cryptic species diversity.) Twenty-seven Eurasian taxonomic, descriptive, distributional, and biological references for C. obsoletus are listed in Arnaud 1956: 116.

Ceratopogon obsoletus Meigen, 1818: 76 (Europe) . (Twelve Eurasian and African synonyms are listed in Borkent and Dominiak 2020: 105.)

Culicoides obsoletus (Meigen) : Root and Hoffman 1937: 155 (in part; key; female; male genitalia; fig. male genitalia is that of C. sanguisuga ). James 1943: 148 (seasonal distribution; Colorado). Wirth 1951: 77 (key; female; fig. wing, palpus, spermathecae). Wirth 1952a: 169 (key; female; male genitalia; fig. female wing, palpus). Rees and Bullock 1954 (Utah: Salt Lake County). Foote and Pratt 1954: 29 (in part; key; diagnoses of female, male, pupa, larva, egg; bionomics; fig. wing, mesonotum, spermathecae [fig. female palpus, male genitalia represent C. sanguisuga ]).

Culicoides (Culicoides) obsoletus: Khalaf 1954: 39 (assignment to subgenus Culicoides ).

Culicoides (Avaritia) obsoletus: Fox 1955: 218 , 248 (subgenus Avaritia Fox ; designated C. obsoletus as type species; key and diagnoses of subgenera; species diagnosis; taxonomy). Jamnback and Wirth 1963: 188 (key; female, male, pupa, larva; fig. female palpus, antenna, male genitalia, male pupa, female pupa, larva). Jamnback 1965: 84 (key; female; male genitalia; larva; biology; fig. male genitalia, female wing, antenna, palpus, eye, pupa). Atchley 1967: 969 (key; female; male genitalia; fig. female wing, palpus, spermathecae, male genitalia, parameres; biology). Childers and Wingo 1968: 16 (key; biology; fig. female wing, spermathecae). Jorgensen 1969: 20 (quantitative characters; key; female, male; seasonal distribution; fig. female antenna, palpus, spermathecae, wing, male genitalia, parameres). Battle and Turner 1971: 64 (female; male genitalia; larval habitats; feeding habits; seasonal distribution; fig. female eye separation, palpus, wing, spermathecae, male genitalia, parameres). Downes and Wirth 1981: 407 (fig. female palpus). Wirth et al. 1985: 14 (numerical characters; fig. female wing). Murphree and Mullen 1991: 318 (key; larva; numerical characters; fig. epipharynx, hypostoma, caudal segment). Mathieu et al. 2020: 10 (phylogenetic analysis of subgenus Avaritia found no evidence of cryptic species diversity within C. obsoletus ).

Culicoides sp. near obsoletus: Bullock 1952: 16 (key; female; male genitalia; August, September; Utah: Salt Lake County). Jones 1961a: 730 (key; pupa; fig. chaetotaxy, operculum, respiratory trumpet; Wisconsin).

Diagnosis. ( Tables 14, 15) Wing pattern faint on distal third; pale spot over distal half of r 2; eyes contiguous, bare; superior transverse suture absent; palpal segment 3 with sensory pit; two ovoid subequal spermathecae with necks and vestigial spermatheca; posterior margin of male sternite 9 cleft, without broad excavation; posterior margin of male tergite 9 convex, without apicolateral processes; ventral apodeme of gonocoxite simple, ~2× longer than dorsal apodeme, slender, ~7× longer than basal width; aedeagus broadly U-shaped, without sclerotized membrane between basal arms or sclerotized anterior-directed point at base of short median process; median process with bare convex tip; aedeagal ratio ~0.8; parameres separate, curved, pointed, tipped with tiny spines.

Distribution. Holarctic, Eurasia, North Africa, North America from Alaska, British Columbia, Alberta, Ontario, Quebec, south to Northern California (and into Southern California along the cooler Pacific coast), Utah (Salt Lake County), Colorado ( Monarch 2021), New Mexico, Oklahoma, Tennessee, Georgia. Habitat records indicate it prefers mountain coniferous forests ( Wirth 1952a; Atchley 1967; Sprygin 2014). Culicoides obsoletus was not collected, though seemingly suitable habitats were sampled several times in Utah, Idaho, Wyoming, Colorado, and Arizona ( Tables 2, 3), suggesting it is relatively rare or in only scattered populations south of the northern coniferous forests of western North America. However, Bullock (1952) collected adults during August and September in Salt Lake County, Utah.

Larval ecology. It is likely that some of the biological accounts for Nearctic C. obsoletus prior to 1963 apply to C. sanguisuga . Reports that immatures have been collected or reared from a flowing water spring ( Wirth 1952a), treeholes with decaying matter, and sandy stream banks, but mostly shaded piles of composting leaves ( Murray 1957), damp terrestrial habitats, manure piles, and a mound of decomposing cornstalks ( Jones 1961b) are thus suspect. Reliable records of collections or rearings of immatures include manure-polluted soil, decaying organic matter ( Jamnback and Wirth 1963; Jamnback 1965), a pile of used chicken litter ( Hair et al. 1966), and leaf litter in a drainage ditch ( Childers and Wingo 1968). Zimmer et al. (2013) characterized its larval habitats in Belgium and found that higher lignin and insoluble fiber favored larval presence, whereas higher magnesium and calcium negatively correlated with larval presence, which might explain the absence of C. obsoletus from the seemingly suitable, but calcic, agricultural areas of the southwestern United States.

Adult behavior. Culicoides obsoletus is mammalophilic. Reported Nearctic hosts are turkey ( Humphreys and Turner 1973), sheep ( Zimmerman and Turner 1983), horse ( Jamnback 1965), cow ( Jamnback 1965; Schmidtmann et al. 1981; Zimmerman and Turner 1983), domestic rabbit, gray squirrel ( Wright and DeFoliart 1970), elk ( Cervus elaphus Linnaeus , Cervidae ) ( Reeves et al. 2004), and human ( Jamnback and Wirth 1963; Jamnback 1965). Atchley (1967) reported it to be a crepuscular biting pest in the mountains of southern New Mexico. Schmidtmann et al. (1981) reported C. obsoletus strongly preferred biting calves on the belly instead of on the head, back, or legs.

Palearctic hosts include cow ( Bos taurus ), horse ( Equus ferus Linnaeus , Equidae ), sheep ( Ovis aries Linnaeus , Bovidae ) ( Lassen et al. 2012; Martínez-de la Puente et al. 2012; Elbers and Meiswinkel 2015), goat ( Capra aegagrus [Linnaeus], Bovidae ) ( Lassen et al. 2012; Martínez-de la Puente et al. 2012), roe deer ( Capreolus capreolus ), red deer ( Cervus elaphus Linnaeus , Cervidae ), house mouse ( Mus musculus Linnaeus , Muridae ), and human ( Lassen et al. 2012).

Vector potential. Culicoides obsoletus is a vector of bluetongue virus (BTV) in Europe ( Meiswinkel et al. 2004; Mehlhorn et al. 2007; Foxi et al. 2016). Hence, its Nearctic host preferences indicate it may also be a vector of BTV or epizootic hemorrhagic disease virus (EHDV) in North America.

Symbionts. Pagès et al. (2017) found wild-collected C. obsoletus in Spain to be infected with Wolbachia and “ Candidatus Cardinium ” (Sphingobacteriales: Flexibacteraceae ) endosymbionts. Wolbachia can alter dipteran reproduction by killing male embryos, inducing gamete incompatibility, or feminizing genetic males ( Stouthamer 1999); and “ Candidatus Cardinium ” has been found to alter reproduction in parasitoid wasps and is being investigated for its effect on Culicoides (Pilgrim et al. 2020) .

Figures

Figures 63–65. Male genitalia of Culicoides subgenus Avaritia, ventral view. Upper images focused on aedeagus (A). Lower insets focused on caudal margin of tergite 9. Ventral apodeme of gonocoxite labeled (Gcva). Anteriordirected median process of aedeagus circled. 63) C. boydi (Riverside County, CA [BM]). 64) C. chiopterus (MD [FSCA]). 65) C. obsoletus (MD [FSCA]).

Figures 117–125. Male wings of Culicoides subgenera Avaritia and Silvicola. 117) C. boydi (in grayscale) (Riverside County, CA [BM]). 118) C. obsoletus (MD [FSCA]). 119) C. cockerellii (Bonneville County, ID). 120) C. freeborni (San Diego County, CA [BM]). 121) C. lahontan. 122) C. neofagineus (in grayscale) (paratype, Mendocino County, CA [FSCA]). 123) C. neomontanus. 124) C. saltonensis (Imperial County, CA [FSCA]). 125) C. sierrensis (paratype, Modoc County, CA [FSCA]).