Conostigmus obscurus ( Thomson, 1858 )

Trietsch, Carolyn, Mikó, István, Ezray, Briana & Deans, Andrew R., 2020, A Taxonomic Revision of Nearctic Conostigmus (Hymenoptera: Ceraphronoidea: Megaspilidae), Zootaxa 4792 (1), pp. 1-155 : 63-67

Conostigmus obscurus ( Thomson, 1858)

Figs. 34 , 35

Species Comments and History. Thomson (1858) first described Megaspilus obscurus from a male and female collected in Sweden. Kieffer (1907) later transferred the species to Conostigmus . Dessart (1974) redescribed the species, synonymizing Megaspilus arcticus Thomson, 1858 (single female holotype) and Conostigmus syrphorum Kieffer, 1907 (female type missing), as well as redescribing the male and illustrating the male genitalia for the first time. Due to the limited number of specimens, our description is based on a single male specimen (UAM100257610) collected in Alaska and identified as C. obscurus by Paul Dessart.

Variability. We did not observe enough specimens to describe variations, but Dessart (1974) notes that there are slight variations in color, and that females are lighter in color than males.

Differences between Nearctic and Palearctic Populations. We did not observe enough specimens to note variations between Nearctic and Palearctic specimens.

Differences Between Males and Females. Dessart (1974) notes that the males are very similar to the females, with the females lighter in coloration. We did not observe enough specimens to note variations.

Diagnosis. Males of this species can be distinguished from all other Conostigmus in that: the sternaulus is present and short, not reaching 1/2 of the mesopleuron length; the width of the crenulae of the notauli increases more than 2× anteriorly; the medioventral conjunctiva is present (parossiculi independent or fused proximally); and the proximodorsal notch of the cupula is present, arched (inverted U-shape), and longer than wide. Females can be matched to males by the presence of the sternaulus and the width of the crenulae of the notauli increasing more than 2× anteriorly, as this is the only Nearctic species with these two characters.

Conostigmus obscurus has the proximodorsal notch of the cupula present, U-shaped, and longer than wide, which only occurs in C. lepus , C. bipunctatus , and C. triangularis . This species differs from C. lepus in that it lacks the submedial corners of S9 and has sparse lateral setae on the harpe ( C. lepus with submedial corners on S9 and dense lateral setae sparse on harpe), and from C. triangularis in that it does not have bilobed harpe (present in C. triangularis ). Conostigmus bipunctatus is easily distinguished from this species by the absence of the medioventral conjunctiva and the fused parossiculi ( C. obscurus with conjunctiva present and independent parossiculi).

Description. Body length: 1.325 mm. Color hue pattern in male: cranium, mesosoma, metasoma brown; legs, scape, pedicel, flagellomeres ochre to light brown. Color intensity pattern in male: flagellomeres darker than scape and pedicel; mandible lighter than cranium; metasoma lighter than mesosoma and cranium. Color intensity dorsal and ventral to the site of the sternaulus: concolorous. Color intensity pattern of syntergite: petiole neck and anterior region of syntergite concolorus with the posterior region of the syntergite. Foveolate sculpture on body count: absent. Rugose sculpturing count: absent. Rugose region on upper face count: absent.

Antennae: Male scape length vs. pedicel length: 4.0. Male scape length vs. F1 length: 1.2. Male F1 length vs. pedicel length: 3.33. Male F1 length vs. male F2 length: 1.25. Longest male flagellomere: F1. Length of setae on male flagellomere vs. male flagellomere width: setae shorter than width of flagellomeres. Sensillar patch of the male flagellomere pattern: F6–F9.

Head: Head width, dorsal view: equal to or only slightly wider than mesosoma (less than 1.3× wider than mesosoma). Head height (HH, lateral view) vs. eye height (EHf, anterior view): HH:EHf=1.57. Head height (HH) vs. head length (HL): HH:HL=1.38. Head width (HW) vs. interorbital space (IOS): HW:IOS=1.52. Head width (HW) vs. head height (HH): HW:HH=1.14. Cephalic size (csb): Mean: 385 μm. Maximum eye diameter vs. minimum eye diameter: 1.13. POL:OOL: POL equal to or shorter than OOL and ocellar triangle with short base. Male ocular ocellar line (OOL) vs. lateral ocellar line (LOL): OOL:LOL=2.5. Male ocular ocellar line (OOL) vs. posterior ocellar line (POL): OOL:POL=2.0. Male ocular ocellar line (OOL): posterior ocellar line (POL): lateral ocellar line (LOL): 2.5:1.25:1.0. Head shape (anterior view): circular or triangular. Preoccipital lunula count: present. Preoccipital carina count: absent. Occipital carina sculpture: crenulate. Preoccipital furrow count: present. Preoccipital furrow anterior end: preoccipital furrow ends at site of postocellar carina. Preoccipital furrow sculpture: crenulate. Postocellar carina count: present. Dorsal margin of occipital carina vs. dorsal margin of lateral ocellus in lateral view: occipital carina ventral to lateral ocellus in lateral view. Transverse scutes on upper face count: absent. Transverse frontal carina count: absent. Randomly sized areolae around setal pits on upper face count: absent. Setal pit on vertex size: smaller than diameter of scutes. Ventromedian setiferous patch and ventrolateral setiferous patch count: absent. White, thick setae on upper face count: absent. Antennal scrobe count: absent. Facial structure count: facial pit present. Facial pit count: present. Facial sulcus count: absent. Median facial keel count: absent. Supraclypeal depression count: present. Supraclypeal depression structure: present medially, inverted U-shaped. Intertorular area count: present. Intertorular carina count: present. Median process on intertorular carina count: present. Median process on intertorular carina shape: acute. Median process of intertorular carina structure: process does not extend across intertorular area to dorsal margin of clypeus. Median region of intertorular area shape: convex. Ventral margin of antennal rim vs. dorsal margin of clypeus: not adjacent. Torulo–clypeal carina count: present. Subtorular carina count: absent. Mandibular tooth count: 2. Mandibular lancea count: absent.

Mesosoma: Weber length: WL=550 μm. Anterior mesoscutal width (AscW) vs. posterior mesoscutal width (PscW): AscW/PscW=0.6. Mesoscutal length (MscL) vs. anterior mesoscutal width (AscW): MscL/AscW=1.5. Mesoscutal length (MscL) vs. mesoscutellar length (MscIL): MscL:MscIL= 0.82. Wing count: present. Fore wing size: wings present and macropterous with apex extending past petiole. Pronotum median length: less than longest median anatomical line of the mesoscutum. Notaulus count: present. Crenulae of notaulus width: width of the crenulae does not increase more than 2× anteriorly. Notaulus posterior end location: adjacent to transscutal articulation. Posterior region of notaulus orientation: posterior end of notaulus does not curve and is not adjacent to median mesoscutal sulcus. Median mesoscutal sulcus count: present. Median mesoscutal sulcus posterior end: adjacent to transscutal articulation. Scutoscutellar sulcus vs. transscutal articulation location: adjacent. Axillular carinae count: present. Axillular carinae shape: the left and right carinae are separated posteromedially. Speculum ventral limit: not extending ventrally of pleural pit line. Metapleural sulcus shape: straight. Mesometapleural sulcus count: present. Ventrolateral invagination of the pronotum count: present. Sternaulus count: present. Sternaulus length: short and not reaching 1/2 of mesopleuron length at level of sternaulus. Sternaulus sculpture: smooth. Epicnemial carina count: complete. Epicnemium posterior margin shape: anterior discrimenal pit present; epicnemial carina curved. Transverse striations on the ventral metapleural area count: absent. Scutes on posterior region of mesoscutum and dorsal region of mesoscutellum convexity: flat. Ventral projection of the metapleural carina count: absent. Lateral propodeal carina count: present. Lateral propodeal carina shape: inverted “Y” (left and right lateral propodeal are adjacent medially posterior to antecostal sulcus of the first abdominal tergum, and connected to the antecostal sulcus by a median carina representing the median branch of the inverted “Y”). Mesopostscutellum count: absent (scutellum flat). Anteromedian projection of the metanoto–propodeo–metapecto–mesopectal complex count: absent. Posterior margin of nucha in dorsal view shape: straight.

Metasoma: Transverse carina on petiole shape: concave. Paired blue iridescent ovoid patches on the syntergite count: absent. Shortest width of petiole neck vs. syntergal translucent patch maximum width: 1.86. Syntergal translucent patch maximum width vs. minimum width: 1.4. Syntergal translucent patch maximum width orientation: anterolaterally. Synsternal setiferous patch shape: linear, with a patch of setae lateral or posterior to the synsternal translucent patch. Synsternal setiferous patch structure: comprised of a single or double row of setae anterior and lateral to the synsternal translucent patch, with a patch of setae posterior to the synsternal translucent patch. Synsternal setiferous patch anterior end: synsternal setiferous patch begins anterior to the synsternal translucent patch anterior margin. Synsternal setiferous patch posterior end: synsternal setiferous patch ends posterior to the synsternal translucent patch posterior margin. Synsternal setiferous patch length vs. synsternal translucent patch maximum width: synsternal setiferous patch at least as long as the maximum width of the synsternal translucent patch but not 2× as long. S1 length vs. shortest width: S1 wider than long.

Male Genitalia: Distal margin of male S9 shape: convex. Proximolateral corner of male S9 shape: blunt. Male S9 distal setal line/setal patch count: distal setae composing transverse setiferous line or lines. Male S9 distal setal line / setal patch structure: single or double transverse row of setae, sometimes with fewer setae medially to form two separate patches. Submedial projections on proximal margin of S9 count: absent. Cupula length vs. gono-style–volsella complex length: cupula less than 1/2 the length of gonostyle–volsella complex in lateral view. Proximodorsal notch of cupula count: present. Proximodorsal notch of cupula shape: arched (inverted U-shape). Proximodorsal notch of cupula width vs length: longer than wide. Proximolateral projection of the cupula shape: blunt. Gonocondyle count: present. Gonocondyle shape: acute. Distodorsal margin of cupula shape: concave. Distoventral submedian corner of the cupula count: absent. Dorsomedian projection of the gonostyle–volsella complex count: absent. Dorsomedian conjunctiva of the gonostyle–volsella complex count: present. Dorsomedian conjunctiva of the gonostyle–volsella complex length relative to length of gonostyle–volsella complex: dorsomedian conjunctiva extending more than or equal to 2/3 of length of gonostyle–volsella complex in dorsal view. Dorsomedial margin of gonostyle–volsella complex shape: V-shaped. Proximal end of dorsomedian conjunctiva of the gonostyle–volsella complex shape: acute or V-shaped. Parossiculus count or parossiculus and gonostipes fusion: present and parossiculi not fused with the gonostipes. Medioventral conjunctiva of the gonostyle–volsella complex count or fusion of parossiculi: medioventral conjunctiva present and parossiculi independent or fused proximally. Apical parossicular setae count: one. Distal projection of the parossiculus count: absent. Distal projection of the penisvalva count: absent. Gonossiculus spine count: 2. Gonossiculus spine length: one spine not more than 2× as long as the other(s) (spines of similar lengths). Harpe length: harpe shorter than gonostipes in lateral view. Harpe shape: simple and not bilobed. Harpe orientation: medial. Lateral margin of harpe shape: widest point of harpe is at its articulation site with gonostyle–volsella complex. Distal margin of harpe in lateral view: acute or pointed. Lateral setae of harpe count: present. Lateral setae of harpe orientation: oriented distally. Lateral setae on harpe density: setae sparse. Dense patch of setae on the distoventral edge of the harpe count: absent. Distodorsal setae of sensillar ring of harpe length vs. harpe width in lateral view: setae as long as or shorter than harpe width. Distodorsal setae of sensillar ring of harpe orientation: distomedially. Sensillar ring area of harpe orientation: distomedially. Sensillar ring shape: circular. Distoventral margin of harpe in lateral view: convex.

Distribution. Holarctic.

Material Examined. Non-type material (1 male): USA: Alaska: UAM100257610 ( UAM) .

Figures

FIGURE 34. Conostigmus obscurus (Thomson, 1858) male (UAM100257610).A. Lateral view. B. Dorsal view.Abbreviation: sternaulus (ste).

FIGURE 35. Conostigmus obscurus (Thomson, 1858) male genitalia (UAM100257610). A. Ventral view. B. Dorsal view.