Conostigmus triangularis ( 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 : 88-90

Conostigmus triangularis ( Thomson, 1858)

Figs. 47 , 48

Species Comments and History. Thomson (1858) described the species from material in Lund, Sweden, deposited in the NHRS. Kieffer (1907) described another species, Trichosteresis armata Kieffer , from male and female specimens deposited in the HNHM that Dessart (1974) later synonymized with triangularis . Other species that Dessart synonymized with triangularis include Conostigmus ater Fouts 1926 and Conostigmus zaglouli Kamal 1926 ( Dessart, 1980b, 1981); the specimens of both synonymous species are deposited in the USNM.

The female holotype of C. ater Fouts is point mounted and missing its metasoma; this damage is not mentioned in Masner and Muesebeck (1968) and must have occurred since then. There is also one female paralectotype in good condition. The female holotype specimen of C. zaglouli Kamal 1926 is point mounted and missing the last three flagellomeres on the right antenna. There is also one male allotype and 5 female paratypes, which are all damaged to various degrees and missing pieces as Masner and Muesebeck (1968) noted. Two female paratypes (USN- MENT 01212973; USNMENT 01212971) even have extra antennae glued on the point mounts that may have come from other specimens in the type series.

Thomson (1858) originally named this species triangularis after the triangle-shaped pterostigma, though this character is found in many Megaspilidae and is not particularly useful as a defining character for the species. Rather, the most unique defining character of this species is the male harpe, which are bilobed. This character state is not known in any other Conostigmus species worldwide, though it does occur in some Dendrocerus species, including D. penmaricus (illustrations in Dessart, 1995a) and D. rodhaini (illustrations in Dessart, 1978).

Conostigmus triangularis is a very Dendrocerus -like species in that it lacks a sternaulus, the ocellar triangle can appear obtuse (POL longer than LOL, ocellar triangle with a wide base), and the metapleural sulcus can appear arched in some specimens (including USNMENT01339809 and USNMENT01339808, the types from Fouts and Kamal). However, C. triangularis is not a Dendrocerus species in that it has the facial pit present, the parossiculi present (parossiculi and gonostipes not fused) and the medioventral conjunctiva of the gonostyle–volsella complex present (parossiculi independent). While the facial pit occurs in some Dendrocerus species, such as D. carpenteri and D. rectangularis , there are no Dendrocerus species with independent parossiculi.

Variability. The metapleural sulcus is arched in some specimens (USNMENT01339809, USNMENT01339808) and straight in others (PSUC_FEM 9773).

Differences between Nearctic, Palearctic and Afrotropical Populations. We did not note any differences between Palearctic and Nearctic specimens. We did not examine any Afrotropical specimens.

Differences Between Males and Females. Other than genitalia differences and sexual dimorphism in the antennae, there are no obvious differences between males and females.

Diagnosis. Males of this species are easily recognizable by the bilobed male harpe, which does not occur in any other known Conostigmus species. Another unique character is the transverse striation present and limited to the dorsal half of the ventral metapleural area. This character can be used to match males and females. Other characters that can be used to recognize the species and match males to females include the absence of the sternaulus and presence of the facial pit.

The most similar species to C. triangularis is C. lepus , another Dendrocerus -like species that also has the sternaulus absent and facial pit present. Conostigmus triangularis and C. lepus can easily be distinguished by the male genitalia. Conostigmus lepus has simple harpe (not bilobed), submedial projections on the proximal margin of S9 present (absent in C. triangularis ) and dense lateral setae on the harpe that are evenly distributed across the entire lateral surface of the harpe (lateral setae sparse in C. triangularis ). Females of both species can be distinguished by the extent of the transverse striations on the ventral metapleural area; the transverse striations occur across the entire ventral metapleural area in C. lepus , whereas they are limited to the dorsal half of the ventral metapleural area in C. triangularis .

Description. Body length: 2.1–2.8 mm. Color hue pattern in male: cranium, mesosoma, scape brown to dark brown; pedicel, mandible, flagellomeres and legs light brown; metasoma reddish-brown. Color intensity pattern in male: pedicel lighter than scape. Color hue pattern female: cranium and mesosoma reddish-brown to dark brown; metasoma reddish-brown; scape, pedicel, flagellomeres light brown to dark brown; legs ochre to brown. Color intensity pattern female: legs lighter than the flagellomeres, scape and pedicel. 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: 3.2–3.4. Male scape length vs. F1 length: 1.6–1.7. Male F1 length vs. pedicel length: 2.0. Male F1 length vs. male F2 length: 1.3–1.5. Longest male flagellomere: F1. Female scape length vs. pedicel length: 3.4–5.0. Female scape length vs. F1 length: 2.5–3.0. Female F1 length vs. F2 length: 1.3–1.7. Female F1 length vs. pedicel length: 1.3–2.0. Longest female 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: F5–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): male HH:EHf=1.5–1.7; female HH: EHf=1.2–1.5. Head height (HH) vs. head length (HL): HH:HL=1.1–1.5. Head width (HW) vs. interorbital space (IOS): male HW:IOS=1.7–1.9; female HW:IOS=2.0–2.2. Head width (HW) vs. head height (HH): HW:HH=1.3–1.5. Cephalic size (csb): Mean: 430–710 μm. Maximum eye diameter vs. minimum eye diameter: 1.1–1.4. POL:OOL: POL longer than OOL and ocellar triangle with wide base. Male ocular ocellar line (OOL) vs. lateral ocellar line (LOL): OOL:LOL=2.0–2.5. Male ocular ocellar line (OOL) vs. posterior ocellar line (POL): OOL:POL=0.8–1.0. Male ocular ocellar line (OOL): posterior ocellar line (POL): lateral ocellar line (LOL): 2.0–2.5:2.2–2.5:1.0. Female ocular ocellar line (OOL) vs. lateral ocellar line (LOL): OOL 1.8–2.0× as long as LOL. Female ocular ocellar line (OOL): posterior ocellar line (POL): lateral ocellar line (LOL): 1.8–2.0:1.8–2.3:1.0. Head shape (anterior view): circular or triangular. Preoccipital lunula count: present. Preoccipital carina count: absent. Occipital carina structure: occipital carina not complete. Occipital carina sculpture: crenulate. Preoccipital furrow count: present. Preoccipital furrow anterior end: preoccipital furrow ends at anterior ocellus. Preoccipital furrow sculpture: crenulate. Postocellar carina count: absent. 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: absent medially, represented by two grooves laterally of facial pit. Intertorular area count: present. Intertorular carina count: present. Median process on intertorular carina count: present. Median process on intertorular carina shape: blunt. 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: adjacent. Torulo–clypeal carina count: absent. Subtorular carina count: absent. Mandibular tooth count: 2. Mandibular lancea count: absent.

Mesosoma: Weber length: WL=670–950 μm. Anterior mesoscutal width (AscW) vs. posterior mesoscutal width (PscW): AscW/PscW=0.7–0.9. Mesoscutal length (MscL) vs. anterior mesoscutal width (AscW): MscL/ AscW=1.4–1.9. Mesoscutal length (MscL) vs. mesoscutellar length (MscIL): MscL:MscIL= 0.9–1.1. 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 curves and is 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: absent. Speculum ventral limit: not extending ventrally of pleural pit line. Metapleural sulcus shape: straight or arched. Mesometapleural sulcus count: present. Ventrolateral invagination of the pronotum count: present. Sternaulus count: absent. Sternaulus length: sternaulus absent. Epicnemial carina count: complete. Epicnemium posterior margin shape: anterior discrimenal pit absent; epicnemial carina curved. Transverse striations on the ventral metapleural area count: present. Transverse striations on the ventral metapleural area ventral limit: transverse striations limited to dorsal half of ventral metapleural area. 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: present. Posterior margin of nucha in dorsal view shape: concave.

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: 2.2–2.8. Shortest width of petiole neck vs. synsternal translucent patch maximum width: 2.57 (PSUC_FEM 9773). Syntergal translucent patch maximum width vs. minimum width: 1.4–2.3. Syntergal translucent patch maximum width orientation: anterolaterally. Synsternal translucent patch maximum width orientation: anterior–posteriorly. 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 to the synsternal translucent patch, with a patch of setae lateral or 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 2× as long as the maximum width of the synsternal translucent patch. S1 length vs. shortest width: S1 wider than long.

Male Genitalia: Proximolateral corner of male S9 shape: acute. Male S9 distal setal line/setal patch count: distal setae composing transverse setiferous line or lines. Distomedian hairless area interrupting transverse row of setae or patch on male S9 count: present with distal setiferous patch/line separated medially. Submedial projections on proximal margin of S9 count: absent. Cupula length vs. gonostyle–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: at least two times as long as wide. Proximolateral projection of the cupula shape: blunt. Gonocondyle count: present. Gonocondyle shape: blunt. 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 equal to or less than 1/3 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: 3. 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: bilobed. Lateral margin of harpe shape: widest point of harpe is in its distal 1/3rd. Distal margin of harpe in lateral view: two acute or pointed lobes of harpe. Lateral setae of harpe count: absent. Lateral setae on harpe density: setae sparse. Dense patch of setae on the distoventral edge of the harpe count: absent. Distal setae on harpe length: setae of equal length across distal end of harpe. 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: distoventrally. Sensillar ring area of harpe orientation: distoventrally. Sensillar ring shape: elongate. Distoventral margin of harpe in lateral view: harpe bilobed and distoventral margin concave between lobes.

Distribution. Holarctic and Afrotropical.

Material Examined. Holotype female: SWEDEN: NHRS-HEVA000006796 ( NHRS). Synonymized types: USA: California: USNMENT01339809, 01212968, 01339808, 01212961, 01212971, 01212970, 01212974, 01212973 ( USNM).

Non-type material (3 males, 5 females): UNITED ARAB EMIRATES: 1 male. IM 1836 ( NCSU) . USA: California: 1 female. UCRC _ ENT 00457054 ( UCRC) . USA: New York: 1 male, 1 female. PSUC _ FEM 8810 , 9773 ( ROME) . USA: Wisconsin: 1 male, 3 females. PSUC _FEM 50074, 50186 , 50297 , 84299 ( WIRC) .

Figures

FIGURE 47. Conostigmus triangularis (Thomson, 1858). A. Lateral view of the male (PSUC_FEM 9773). B. Lateral view of the female former type specimen of C. ater Fouts, synonym of C. triangularis. (USNMENT01339809). C. Dorsal view of the female former type specimen of C. ater Fouts, synonym of C. triangularis. (USNMENT01339809). Abbreviations: mesopostscutellum (mpm); preoccipital lunula (pou); transverse striations on ventral metapleural area (trs).

FIGURE 48. Conostigmus triangularis (Thomson, 1858) male genitalia (PSUC_FEM 148624). A. Ventral view. B. Lateral view, showing the bilobed harpe. C. Dorsal view.