Culicoides (Monoculicoides) riethi Kieffer

William L. Grogan, Jr. & Lysyk, Timothy J., 2015, A revision of the biting midges in the Culicoides (Monoculicoides) nubeculosus-stigma complex in North America with the description of a new species (Diptera: Ceratopogonidae), Insecta Mundi 2015 (441), pp. 1-24 : 6-9

Culicoides (Monoculicoides) riethi Kieffer

( Fig. 9–21 )

Culicoides Riethi Kieffer, 1914: 237 . Germany.

Culicoides (Monoculicoides) riethi: Khalaf 1954: 40 (in list of species assigned to new subgenus Monoculicoides ).

Culicoides cordatus Kieffer, 1921: 114 . Latvia.

Culicoides crassiforceps Kieffer, 1924: 15 . Germany.

Culicoides gigas Root and Hoffman, 1937: 172 . Canada (Saskatchewan). (New Synonym); Curtis 1940: 19 (British Columbia); Leech 1943: 23 (British Columbia); Downes 1958b: 804 (Alberta; fig. of larval habitat; notes on reproduction, biting humans and dogs).

Culicoides (Monoculicoides) gigas: Wirth 1965: 131 (in Nearctic catalog north of Mexico; distribution); Wirth et al. 1985: 28 (in wing atlas of Nearctic species of Culicoides ; photo of female wing; distribution); Borkent and Grogan 2009: 14 (in Nearctic catalog; distribution).

Diagnosis. A medium to large species of the C. nubeculosus - stigma complex that differs from other Nearctic species in that complex by the following combination of characters: male wing length 1.46–1.74 mm, female wing length 1.55–1.94 mm; wing veins and membrane dark dusky brown with distinct pattern of large pale spots over r-m crossvein and on much of the membrane; fore tibia with sub-basal pale band. Male: tergite 9 tapering slightly distally, apex very broad with wide shallow V-shaped median notch, and slightly to moderately divergent apicolateral processes; gonocoxite short; gonostylus much longer, proximal half stout, abruptly tapered and bent at mid-length with very slender distal half; parameres fused proximally, distal portion bifurcate, each prong nearly straight to sinuate with sharply pointed apex; aedeagus with distal portion deeply bifurcate, each prong apically bifid. Female: mandible well developed, with 9–14 coarse retrorse teeth on inner margin; lacinia with 18–25 coarse, retrorse teeth on outer margin; papal segment 3 moderately slender (palpal ratio 2.20–2.83); fore, mid tibiae with sub-basal pale band; spermatheca ovoid to elongate pyriform, with numerous tiny hyaline punctations. Male. Head: ( Fig. 9 , 15 ) Brown. Eyes widely separated, with fine sparse setae along margins but apparently absent between ommatidia. Antennal flagellum ( Fig. 9 , 16 ) with flagellomeres 1, 11–13 separate, 2–10 fused; flagellomeres 11–13 considerably longer than 2–10, 11 longest; flagellomeres 1, 6–8 with single apical sensilla coeloconica; flagellomeres 1 with 2 rows, 2–13 with single row of sensilla chaetica, those on 2–10 comprising the long, moderately dense plume; combined total lengths of flagellomeres 0.806 (0.742 –0.877, n=5) mm; antennal ratio 0.55 (0.54–0.57, n=5). Palpal segment 3 slender with small, shallow subapical pit bearing a few capitate sensilla; palpal ratio 2.61 (2.27–2.88, n=5). Proboscis moderately short, extending to palpal segment 4, proboscis/head ratio 0.76 (0.67–0.86, n=11); mandible, lacinia vestigial, without teeth. Thorax: Scutum medium dark brown to golden brown without trace of pattern; scutellum lighter brown to golden with 2 submarginal, 3–4 central large setae; postscutellum brown. Femora, tibiae light brown to medium brown; fore tibia with narrow sub-basal pale band; mid, hind tibiae with or without poorly developed sub-basal pale band; claws small, proximal 3/4 straight, distal 1/4 curved, tips bent, apices bifid. Wing ( Fig. 10 , 17 ) similar to but narrower than female wing, pattern of dark and light spots less distinct in some specimens; most of membrane infuscated, covered with coarse microtrichia, which are densest in dark spots; macrotrichia restricted to costa, radius and anterior marginal region of cell r 3, occasionally present on veins M 1, M 2, CuA 1 and in cell m 1; radial cells usually well developed, 1 st narrow, up to twice as long as 2 nd, 2 nd quadrate, dark brown; wing length 1.54 (1.43–1.74, n=5) mm; costal ratio 0.55 (0.53–0.56, n=5). Halter brown to golden. Abdomen: Medium dark brown; pleurae light brown. Genitalia ( Fig. 11 , 18 ) dark brown. Tergite 9 slightly tapering distally; apex very broad with shallow, wide V-shaped median notch; apicolateral process conical, moderately slender, extending beyond apex of gonocoxite, with single small apical seta, apices slightly to moderately divergent (dependent on compression from cover slip); cercus setose with pair of large ventrolateral setae, arising anterior to posterior margin, when flattened due to mounting, may extend well beyond posterior margin. Sternite 9 3 x broader than long; anterior margin straight, posterior margin with moderately narrow V- or U-shaped excavation as deep as ½ of total length of sternite. Gonocoxite straight, 1.5 x longer than broad, tapering slightly distally, dorsal root moderately massive, extending to or beyond proximal level of basal arm of parameres, slightly to moderately recurved laterally. Gonostylus slightly longer than gonocoxite, proximal ½ stout, moderately curved distally, abruptly tapered and bent up to 90 ◦ at mid-length, distal ½ slender, slightly curved, apex roundly pointed. Parameres fused basally, more or less Y-shaped; basal arm moderately to heavily sclerotized, nearly straight, apex folded ventrad; mid portion moderately to lightly sclerotized; distal portion lightly sclerotized, bifurcate, each prong nearly straight to sinuate, apex sharply pointed. Aedeagus Y-shaped; membrane spiculate; basal arm heavily sclerotized, recurved; mid portion heavily sclerotized on margins, ventral surface bare, basal arch curved, extending ¼ of total length of aedeagus; distal portion lightly sclerotized, bifurcate, apex of each half bifid.

Female. Head: ( Fig. 12 , 19 ) Brown. Eyes bare, separated by diameter of 2–3 ommatidia. Antennal flagellomeres brown, 1–8 often paler than 9–13; 9–13 slightly or moderately longer than 2–8, 13 longest; flagellomeres 1, 6–8 with apical single (rarely multiple) large sensilla coeloconica; flagellomeres 1–13 with single sub-basal whorl of moderately long sensilla chaetica, scattered shorter sensilla chaetica and covering of fine pubescence; combined total lengths of flagellomeres 0.655 (0.581 –0.699, n=12) mm; antennal ratio 0.83 (0.71–0.95, n=12). Palpus with segment 3 slender to slightly swollen, slightly longer than segments 4–5 combined, with single small round shallow subapical pit (rarely with 2 smaller pits) bearing numerous capitate sensilla that extend well beyond pit opening; palpal ratio 2.37 (2.20–2.83, n=13). Proboscis moderately long; proboscis/head ratio 0.76 (0.67–0.86, n=11); mandible well developed, with 9–14 coarse retrorse teeth on inner margin; lacinia with 18–25 coarse, retrorse teeth on outer margin. Thorax: Golden brown to dark brown; scutum with two yellowish sutures originating from humeri; scutellum pale to light brown with 6–8 large setae. Fore, mid tibiae with narrow sub-basal pale bands; femoro-tibial joints darkened; tarsomeres 1–3 pale to light brown, 4–5 darker brown; hind tibial comb with 5–6 spines, 2 nd or 3 rd from spur longest. Wing ( Fig. 13 , 20 ) moderately slender; membrane darkly infuscated, covered with fine pale microtrichia in light spots and streaks, darker coarse microtrichia in dark spots and on veins; macrotrichia sparsely distributed in all cells, densest in distal regions of cells r 3, m 1 and on most veins; pale spots basad to dark stigma and continuing onto r-m crossvein, a larger spot posterior to stigma and in middle of distal dark spot in cell r 3, elongate pale streaks in cells m 1, m 2 and cua 1, marginal pale spots in cells m 1, m 2, cua 1 and along margin and basal region of anal cell; wing length 1.78 (1.55–1.94, n=13) mm; costal ratio 0.57 (0.55–0.58, n=13). Halter light brown. Abdomen: Light to medium brown. Spermatheca ( Fig. 14 , 21 ) ovoid to elongate pyriform, with numerous tiny hyaline punctations and large opening; spermatheca length 0.074 (0.064 –0.082, n=12) mm.

Distribution. Holarctic; in North America from Alaska to Manitoba, south to British Columbia, Wyoming and Nebraska ( Borkent and Grogan 2009).

Types. Type locality, C. riethi , Germany, “Im Salswasser von Sassendorf und Salzkotten, Westfalen.” ( Kieffer 1914). Type locality of holotype female, C. gigas, Fort a la Corne, Saskatchewan, 53 ◦ 17’ N, 104 ◦ 30’ W (near Kinistino, SE of Prince Albert), 17 July 1925, Kenneth M. King, CNCI (pinned).

Specimens examined. CANADA, Alberta, Brooks , 2 June 1955, J. A. Downes, 1 female, 1 male ; Lethbridge , 20 July 1955, J. A. Downes, at light ( JAD 218 /213/18), 1 female . UNITED STATES: MON- TANA, Sheridan Co., Medicine Lake, 9 June 1969, W. W. Wirth, 1 female, 1 male, with pupal exuviae. NEBRASKA, Cherry Co. , Pelican Lake , 2 June 1969, W. W. Wirth, light trap, 1 female ; same data except Twin Lake, alkali lake, 1 female, 1 male with pupal exuviae. Garden Co., Crescent Lake Refuge nr. Pellin Lake , 28-VI-1994, F. R. Holbrook, 1 female, 1 male. NORTH DAKOTA, Burleigh Co. , Long Lake , 4 June 1969, W. W. Wirth, 4 females. SOUTH DAKOTA, Campbell Co. , 21-27-VIII-2002, BTSPP, 46056, ABADRL, 2 females, 1 male. WYOMING, Park Co. , Roberts Ranch nr. Cody, 1 st place on E side of hwy 120, 21-VII-(19)86, 1 female . FRANCE, Ardennes, Viller-Le Tourneur, Light trap 08 PL 15 , 3-4 October 2011, coll. J. C. Delécolle, 1 male. Moselle , Marsal , Emergence 4494P175, 12 May 2011, coll. J. C. Delécolle, 1 male. Vosges , Frenelle-La Grande , Light trap 88 PL2 , 1-2 August 2011, coll. J. C. Delécolle, 1 female . POLAND, Dolina Bedkowska, k. Krakowa, 3-VII-1983, R. Szadziewski , 1 female. Plw. Helski, n. Zatoka Wladyslawowo, 23-VI-1979, R. Szadziewski, light trap, 2 females, 4 males. Silec, Distr. Ketrzyn, 2-14-VIII-1979, R. Szadziewski, light trap near buildings, 1 female .

Discussion. Root and Hoffman (1937) described the legs of the holotype female of C. gigas as being “uniformly yellowish brown”; however, our examination of Nearctic males and females revealed pale bands on at least the fore tibia in males, and fore and mid tibiae in females. We compared our Nearctic specimens of C. gigas with specimens of C. riethi from France ( Figs. 15–21 ) and Poland and found them to be virtually identical in size, coloration, pale tibial bands, wing pattern, male genitalia and female spermatheca. Therefore, we consider Culicoides gigas Root and Hoffman a junior synonym of Culicoides riethi Kieffer (new synonym).

The possibility that C. gigas and C. riethi might be conspecific was mentioned in a letter by Willis Wirth to Antony Downes of 31 October 1993 in which Wirth wrote “In the dim recesses of my memory I recalled that someone, probably you, mentioned the similarity of Culicoides gigas to riethi, so I dug out all of my slides and gave them a good look. I really can find no substantial differences including pupae. I have about half a dozen good slides of riethi from Europe…and a dozen slides of gigas. …. Do you think gigas and riethi are conspecific?” Through the courtesy of Art Borkent and Jeff Cumming, we have a handwritten letter that Downes apparently sent to Wirth ca. late 1993 or 1994, prior to Dr. Wirth’s death on 3 September 1994. Although it is 2.5 pages in length, Downes’s letter only deals with their possible collaboration in describing two undescribed species of C. ( Monoculicoides ) from North America: “sp. 113” that Grogan and Phillips (2008) described as C. grandensis (see below), and, C. shemanchuki , new species, described above.

Bionomics. Downes (1958b) also provided detailed observations of reproduction in several species of Culicoides in southern Alberta (Brooks and Macleod) and northeastern Manitoba (Churchill). He included a photograph of a highly saline slough at Brooks, Alberta, a breeding site of C. riethi (as C. gigas ) and another species in the subgenus Monoculicoides , C. sonorensis (as C. variipennis albertensis Wirth and Jones ). We include some of Downes’ (1958b) observations below.

“The evidence obtained by sampling the larvae at intervals during the season suggests that at least two of the species occurring at Churchill have a life cycle of two years, with the first winter spent as a young, and the second as a full-grown, larva.

“The prairie fauna is also extensive, and again includes a number of undescribed species. Larvae of several species are abundant around the margins of sloughs, often of high salt content…At Brooks and Macleod, in southern Alberta, repeating the experience at Churchill, four autogenous species were discovered; and these four produced very high populations. Perhaps in the prairies there is commonly a sufficiency of rich larval habitats together with a scarcity, or only occasional abundance, of vertebrate hosts; certainly, moreover flight of the adults is severely restricted by the prevailing wind conditions.

“In Culicoides gigas the first ovarian cycle is completed without a blood meal, but since (at Brooks) the species also bites man very readily, it seems probable that it then proceeds to a second ovarian cycle which depends on this blood meal, thus resembling Culex molestus Forskål among the mosquitoes. A very distinctive oviposition flight takes place before sunset, during which the insects fly along a narrow zone of the margin of the pool at the height of a few inches only, ultimately alighting on the blackish soil to deposit their eggs…

“At some of the alkaline sloughs in southern Alberta, C. gigas is accompanied by the related C. variipennis albertensis Wirth and Jones and by a new species of the same group. The latter is not only autogenous but has markedly reduced mouthparts. ...its mating behavior is also aberrant, and the species provides an interesting example of correlation of atypical features of structure, physiology, ecology, and behavior,…” This autogenous species with reduced mouthparts refers to C. shemanchuki , new species.

Regarding the larval habitat of C. riethi in Great Britain, Edwards (1939) wrote “ C. riethi , as far as known at present, is confined to coastal marshes.” and “The larvae are recorded by continental observers as occurring in salt water, presumably on the muddy margins of tidal creeks and pools.” In his review of the distribution and biology of British Culicoides, Boorman (1986) noted that “This species is often found in coastal salt marshes, although it is by no means confined to such habitats. It has been maintained as a laboratory colony, under which conditions it was autogenous.”

Figures

Figures 9–11. Culicoides riethi, male, from Warner, Alberta, Canada. 9) Head. 10) Wing. 11) Genitalia.

Figures 12–14. Culicoides riethi, female, from Warner, Alberta, Canada. 12) Head. 13) Wing. 14) Spermatheca.

Figures 15–18. Culicoides riethi, male, from Vosges, France. 15) Head. 16) Antenna. 17) Wing. 18) Genitalia.

Figures 19–21. Culicoides riethi, female, from Vosges, France. 19) Head. 20) Wing. 21) Spermatheca.