Mesembrina latreillii Robineau-Desvoidy, 1830,
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|Mesembrina latreillii Robineau-Desvoidy, 1830|
Figs. 1View FIGURE 1 B, 1 E, 1 H, 4 A –G, 6 A
Mesembrina latreillii Robineau-Desvoidy, 1830: 401 . Eumesembrina latreillei [sic]; Townsend 1908: 124. Eumesembrina alascensis Townsend, 1908: 124 .
Diagnosis: One of the smaller species with thoracic and abdominal setae entirely black ( Fig. 1View FIGURE 1 B); gena dusted silver to brownish pollinose, three dusted white lines on prescutum present, M 1 vein ending well past wing apex ( Fig. 1View FIGURE 1 E). Females can usually be separated from the Palaearctic M. resplendens resplendens by the presence of 2 patches of short fine hair on dorsal surface of the fifth abdominal tergite (Fig. 6 A).
Type material examined: Eumesembrina alascensis – Holotype Ψ labeled “Kukak Bay / Alaska, July 4 ’ 99 ”; “Harriman Expedition ’ 99 / T. Kincaid, Collector”; “ Mesembrina latreillei [sic] / Desv.”; “ Type / No. 10897 / U. S. M. N.”; “ Eumesembrina alascensis / Type Towns” ( USNM).
In the original description of M. latreillii, Robineau-Desvoidy (1830) states that the original material for this species is from Nova Scotia and deposited in the Dejean collection. It appears, however, that the type (s) are now lost or destroyed (A.C. Pont, pers. comm.).
Other material examined: 9 ɗ, 94 Ψ: NEARCTIC: Canada: Alberta: Banff, Fort McMurray, Waterton; British Columbia: Agassiz, Cowichan Lake, Kaslo, Liard River, Mt. Allard, Robson, Squamish, Terrace; Manitoba: Belair, Erikson, Gardenton, Gillam; N.W.T.: Aklavik, Fort McPherson, Hay River, Tununuk; Ontario: Algoma Dist., Algonquin Pk., Archie Coulter Con. Area, Black Sturgeon Lake, Chatterton, Dufferin, Eva Lake, Iroquois Falls, Lake Nipigon, Maynooth, Renfrew Co., Sault St. Marie, Temagami; Quebec: Aylmer, Chelsea, Duncan Lake, Gatineau Co., Lac Tremblant Nord, La Verendrye, Mt. St. Hilaire, Mt. St. Marie, Nominingue, Old Chelsea, Mt. Rigaud; Yukon: Burwash Flats, Carcross aspen parkland; USA: Alaska: Anchorage, Juneau, Kodiak, Kodiak Island, Livengood, Mt. McKinley Nat. Pk., Saldovia; Michigan: Copper Harbour; Idaho: Moscow Mt.; New Hampshire: Mt. Adams, Mt. Madison, Mt. Prospect, Mt. Washington; New York: Maplecrest, Hopk; North Carolina: Bryson, Great Smoky Mts. Nat. Pk., Highlands, Mt. Michell; Pennsylvania: Tamarak; Tennessee: Clingman’s Dome, Gatlinburg, Great Smoky Mts. Nat. Pk., Indian Gap; Virginia: Blue Ridge Mts.; Washington: Cascade Mts., Mt. Baker Lodge, Mt. Rainier, Port Ludlow, Quilcene, Seattle ( JBWM, CNC, BMNH, MZLU).
Description: Male: body length 8.8–10mm.
Head: Background color black, parafacial dusted silver, gena dusted silver to brownish; eye sparsely haired; distance between eyes 1.2–1.3 x distance between the outer margins of the posterior ocelli; frons with 8–10 fine black medioclinate fr, usually 2 strong proclinate orb, surrounded by many fine proclinate, reclinate or medioclinate orb 0.5 x the length of larger orb and extending half of the way down the frons; tuft of short black setae posterior to ocellar triangle, 1 i vt and 1 pavt both convergent; palpus ranging in color from orange to black, 7.0x as long as wide; pedicel dark orange to brown, haired and with 2 setae, more than 2.0x length of others; first flagellomere 3.5–4.5 x as long as wide and ranging in color from orange to black; basal half of arista thickened and often yellow; prementum haired and glossy, 2.0x as long as wide.
Thorax: Appearing glossy black but with a faint metallic greenish coloration; covered in fine black hair and setae, postpronotal lobes and medial portion of prescutum with silvery dust appearing as three distinct lines; anepimeron haired with a tuft of longer hairs on dorsal edge; 1 + 2 acr, 3 + 4 dc, 1 + 2 ial, 1 + 4–5 spal, 3 npl, 2 pal; anepisternum bare anteriorly; 1 a kepst, 3 p kepst anterior-most weaker; postpronotum haired with 2–3 strong ppnl; scutellum glossy black to reddish, scutellar setae black, 1 apical sctl, 7 lateral sctl.
Legs: Mostly black with faint metallic greenish coloration, fifth tarsomere lightly yellowish and flattened on all legs; pulvilli large, 2.0x as long as wide; F 1 with 1 row of equal pd on apical two-thirds, 1 row of p decreasing in size from base and 1 complete row of sub-equal v; F 2 with 2–4 p in a group near apex; F 3 with 1 row of sub-equal ad and av, apical third of ad and av rows stronger than basal sections; T 1 with very fine and short a giving surface shiny brown look, 1 strong ad and d near apex and 1 row of equal pd; T 2 ( Fig. 1View FIGURE 1 H) with 1 ad, 5–6 p and 2 v; T 3 with 4–5 av, 5–6 ad, 1 d near apex and 1 long pd near midpoint; fore tarsomeres: 1> 2> 3> 4 <5, with distinct ventral yellow line extending from the midpoint of tarsomere 1 to apex of tarsomere 5; mid tarsomeres: 1> 2> 3> 4 <5, usually without distinct ventral yellow line extending from the midpoint of tarsomere 1 to apex of tarsomere 5 but if line present then usually dull yellow; hind tarsomeres: 1> 2> 3> 4 <5, with very fine brown and short p giving it a shiny look, with or without distinct ventral yellow line.
Wing: ( Fig. 1View FIGURE 1 E). Mostly clear with heavy yellow tinge on basal half; basicosta yellow; wing veins yellow on basal half, brown on apical half; M 1 vein ending well past wing apex; alula clear; calypters yellow.
Abdomen: Shiny black; densely covered in fine black hairs, third and fourth tergites with l m and 1 row of m m along the posterior margin. Sternite 5 1.1 x as long as wide ( Fig. 4View FIGURE 4. M D).
Postabdomen: Epandrium higher than wide ( Fig. 4View FIGURE 4. M B); mesolobus higher than wide with outer ventral projection longer than inner projection and outer projection with sharp apical tooth-like protrusion ( Fig. 4View FIGURE 4. M A); surstylus short and rounded near apex in posterior view ( Fig. 4View FIGURE 4. M B) and lateral view ( Fig. 4View FIGURE 4. M A); pregonite with base wide and apex slender, with 3 lateral setae ( Fig. 4View FIGURE 4. M C); postgonite with base slightly concave with several small lateral setae and apex rounded, 1.0x as high as width of base ( Fig. 4View FIGURE 4. M C); epiphallus short, 0.5 x as long as phallapodeme with apex rounded ( Fig. 4View FIGURE 4. M C); apex of phallapodeme bulb-shaped ( Fig. 4View FIGURE 4. M C); ejaculatory apodeme well sclerotized; lateral sclerites of distiphallus broad and weakly sclerotized, apical section of lateral sclerites with sparse spinules ( Fig. 4View FIGURE 4. M C).
Female: body length 7.0–11.0mm. Differs from male as follows:
Head: Distance between eyes 5.0x distance between the outer margins of the posterior ocelli, tuft of short setae posterior to ocellar triangle black, frontal vitta black to shiny brownish, with many fine setae present; 6– 8 medioclinate fr stronger anteriorly, usually 2 strong proclinate orb located medially and usually 2 strong reclinate orb located posteriorly, surrounded by many fine proclinate orb 0.5 x length of larger orb and not extending past medial portion of the frontal vitta.
Thorax: As in male.
Legs: Fore tarsomere with or without distinct ventral yellow line extending from the midpoint of tarsomere 1 to apex of tarsomere 5 but if present, then line usually dull, mid and hind tarsomeres usually without distinct ventral yellow line.
Wing: As in male.
Abdomen: Third abdominal tergite with distinguishable row of m m along the margin; fifth abdominal tergite with 2 hard to distinguish patches of very short fine hairs (Fig 6 A).
Postabdomen: Anterior portion of tergite 8 split longitudinally into 2 rectangular parallel rods, posterior plate of tergite 8 with 6–7 robust sub-equal setae ( Fig. 4View FIGURE 4. M E); anterior portion of sternite 8 split longitudinally into 2 club-shaped parallel plates, posterior plate of sternite 8 with 4 robust sub-equal setae ( Fig. 4View FIGURE 4. M F); tergite 10 bare except for 1 or 2 pairs of setae on the posterior margin, if present, medial pair smaller ( Fig. 4View FIGURE 4. M E); cercus bare, cercal pegs small ( Fig. 4View FIGURE 4. M E, 4 F); spermathecae 2.0x as long as wide ( Fig. 4View FIGURE 4. M G).
Distribution: NEARCTIC: Canada: Yukon, Northwest Territories, British Columbia, Alberta, Manitoba, Ontario, Quebec, Labrador; USA: Alaska, Colorado, North Dakota, North Carolina, Washington, Michigan, New Hampshire, Tennessee, New York, Idaho, Virginia, Oregon, Pennsylvania.
Remarks: Mesembrina alascensis has been listed as a synonym of M. latreillii in the work of Huckett (1965 a, 1965 b). However, Huckett never provided a justification for the synonymy. The features previously used to separate M. alascensis and M. latreillii ( Townsend 1908; A.C. Pont, pers. comm.) were: M. latreillii with bright orange palpus and first flagellomere, M. alascensis with black palpus and first flagellomere.
After examination of all available material of M. latreillii and M. alascensis , specimens with intermediate features as well as both extremes of the variability spectrum were found and therefore the color of the first flagellomere and palpus appear to be variable features. There is a visible transition in these structures from orange in Manitoba to black in British Columbia. The area between these provinces is where the majority of specimens with the intermediate states were found. Mesembrina alascensis was described entirely from females but we discovered two males from British Columbia with black first flagellomere and palpus that seemed conspecific. The genitalia of one male were examined and are virtually identical to those of M. latreillii from Quebec. Consequently, we agree that the treatment of M. alascensis as a junior synonym of M. latreillii by Huckett (1965 a, 1965 b) was fully justified.
Hennig (1963) referred to a series of flies from Harbin, NE China as “ resplendens subspecies”, a taxon he noted was close to but distinct from M. latreillii . While no material from Hennig’s original series was examined, one male and six females from Japan and Russia from the BMNH determined by A.C. Pont were studied. The features differentiating “ resplendens subspecies” of Hennig from M. latreillii and other Mesembrina species are marked enough that we did not feel it was necessary to obtain material from the original series. Among some of the most obvious features separating these taxa are the following: in both males and females the gena of M. latreillii is brownish pollinose whereas the gena of “ resplendens subspecies” is silvery pollinose; in males of M. latreillii the distance between the eyes is 1.2–1.5 x distance between the outer margins of the posterior ocelli but in “ resplendens subspecies” the distance between the eyes is 0.8 –1.0x distance between the outer margins of the posterior ocelli; in females of M. latreillii the width of the parafacial at the level of the arista is 1.3–1.5 x the width of the first flagellomere and in “ resplendens subspecies” the parafacial is 1.7–1.8 x the width of the first flagellomere. The full description and formal naming of this species is beyond the scope of this work.
Some researchers have claimed that M. latreillii extends into the Palaearctic Region to Japan ( Séguy 1937; Eldridge & James 1957) and Russia (Kamchatka) ( Huckett 1965 b). Huckett (1965 b) even went further and treated M. resplendens as a synonym of M. latreillii . While we reject the synonymy of these two taxa, we are uncertain of the validity of the Palaearctic records of M. latreillii . We examined a specimen labeled as “ M. latreillii ” from Japan ( USNM) that turned out to be a specimen of “ resplendens subspecies” of Hennig. However, we have not examined the material on which the Kamchatka record ( Huckett 1965 b) was based. In addition, V. Sorokina (pers. comm.) informed us of a series of specimens from Russia that seem to closely match M. latreillii but, unfortunately, these specimens were not available to us. Hennig (1963) suspected that Palaearctic records of M. latreillii were misidentifications of his M. “ resplendens subspecies”. The possibility that M. latreillii has a distribution that extends beyond the Nearctic Region into the eastern Palaearctic thus remains open and the issue will hopefully be resolved when more material from eastern Russia is examined. Further investigation is needed to resolve the taxonomy of the resplendens complex, which includes M. latreillii , M. resplendens resplendens , M. resplendens ciliimaculata , and M. “ resplendens subspecies” of Hennig.
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