Diaeretellus nymphaealis Čkrkić & Kocić & Plećaš & Petrović & Tomanović 2022, sp. nov.

Diaeretellus nymphaealis sp. nov. TomanoviĆ, ČkrkiĆ and PetroviĆ

Figures 1 and 2

Holotype. ♀, Lake of the Isles, Minneapolis, MN, USA, 12 July 2015, leg. M. Plećaš, reared from Rhopalosiphum nymphaeae on Nymphaea odorata. Paratypes: 10♀ 15♂, same data as holotype. Holotype and some paratypes (3♀ 1♂) dissected and slide mounted; rest of paratypes in 96% ethanol. All specimens deposited in the collection of the Institute of Zoology, Faculty of Biology, University of Belgrade.

Diagnosis. Diaeretellus nymphaealis sp. nov. resembles D. palustris in having 13- segmented antennae, and in parasitising R. nymphaeae, but can easily be differentiated from it by a more elongate pterostigma (ratio of length to width of pterostigma 4.80–5.00 in D. nymphaealis sp. nov., while about 4.00 in D. palustris), and a distinctly elongated flagellomere 11 (F11) – length/width ratio in D. nymphaealis sp. nov. 3.4, while about 2 in D. palustris.

Female

Head (Figure 2 (a)). Eyes oval. Malar space equal to 0.4 longitudinal eye diameters. Clypeus oval with 5–6 long setae. Tentorial index (tentoriocular line/intertentorial line) about 0.5. Maxillary palps with 3 palpomeres, labial palps with 1 palpomere. Head width/mesoscutum width 1.3. Antennae 13-segmented, filiform, with semierect setae subequal to half of segment diameter (Figure 1 (a)). Flagellomere 1 (F1) and flagellomere 2 (F2) 2.5 (2.4–2.8) and 2 (1.9–2.1) times as long as wide, respectively; F1 sligthly longer than or equal to F2 (Figure 1 (b)). F1 without longitudinal placodes, F2 with 1–2. Flagellomere 11 (F11) very long, 3.5 times as long as wide, with 10–12 longitudinal placodes (Figure 1 (c)).

Mesosoma. Mesoscutum with incomplete notaulices, visible only in the very beginning of the anterior part, and with two longitudinal rows of setae along the dorsal surface (Figure 2 (b)). Propodeum with a narrow central pentagonal areola (Figure 2 (c)). Upper and lower areola with 4–7 and 0–2 setae, respectively. Fore wing pterostigma narrow and elongate, 4.9 (4.8–5.0) times as long as wide. Distal abscissa of R1 (= metacarpus) subequal to pterostigma length; pterostigma length/R1 length ratio 1.2 (1.1–1.3). Vein M+m-cu visible in some specimens, not visible in others (Figure 2 (g)).

Metasoma. Petiole 2.4 times as long as wide at spiracles, with 11–12 costulae on its anterolateral area and 1–2 long setae near the base on each side. Dorsal surface irregularly rugose (Figure 2 (d)). Ovipositor sheath short, length/width ratio 1.7 (1.6–1.8) (Figure 2 (e)).

Colour. Head brown, mouthparts yellow. Antenna light brown, with a yellow ring at the base of F1. Mesoscutum and propodeum light brown to brown, legs and petiole light brown, metasoma and ovipositor sheaths brown.

Body length. 2.2 mm.

Male

Head. Eyes oval. Malar space equal to 0.36 longitudinal eye diameters. Clypeus oval with 5–6 setae. Tentorial index (tentoriocular line/intertentorial line) about 0.5. Maxillary palps with 3 palpomeres, labial palps with 1 palpomere. Head width/mesoscutum width 1.15. Antennae 16-segmented, filiform, with semierect setae subequal to half of segment diameter. Flagellomere 1 (F1) and flagellomere 2 (F2) 2.2 and 2 times as long as wide, respectively; F1 length equal to F2. F1 and F2 both with 5–6 longitudinal placodes. Flagellomere 11 (F11) very long, 3.4 times as long as wide, with 3–4 longitudinal placodes.

Mesosoma. Mesoscutum with incomplete notaulices, visible only in the very beginning of the anterior part, and with two longitudinal rows of setae. Propodeum with a narrow central pentagonal areola. Fore wing pterostigma narrow and elongate, 5 times as long as wide. Distal abscissa of R1 (= metacarpus) subequal to pterostigma length; pterostigma length/R1 length ratio 1.1. Vein M+m-cu visible in some specimens.

Metasoma. Petiole with 11–12 costulae on its anterolateral area. Dorsal surface irregularly rugose. Genitalia shown in Figure 2 (f).

Colour. Head brown, mouthparts yellow. Antenna light brown. Mesoscutum and propodeum light brown to brown, legs and petiole light brown, metasoma brown.

Body length. 2 mm.

Etymology. The name of the new species is derived from the host plant and host aphid.

Key for the identification of Diaeretellus species based on females

1 Wings not developed (Figure 3 (a)) ... D. ephippium (Haliday, 1833)

- Wings normally developed (some forms are micropterous) .............................................. 2

2 Flagellomeres very short and stocky (Figure 3 (b)) ..... ..... D. heinzei (Mackauer, 1959) * - Flagellomeres elongated .................................................................................................................. 3 3 Antenna 14-segmented, F1 length/width ratio 3.3–3.4 (Figure 3 (c)); R1 length equal to pterostigma length (Figure 3 (d)) ...................................... D. macrocarpus Mackauer, 1961

- Antenna 12–13-segmented, F1 length/width ratio 2.17–2.8 (Figures 1 (a,b) and 4(a,b)); R1 shorter than pterostigma length (Figures 2 (g) and 4(d)) .............................................. 4

4 F1 length/width ratio 2.17–2.33; petiole length/width ratio 2.9, some forms are micropterous ...................... ...................... D. svalbardicum Chaubet and Tomanović, 2013

- F1 length/width ratio 2.5–2.8 (Figures 1 (b) and 4(b)); petiole length/width ratio 2–2.5 (Figures 2 (d) and 4(c)) ........................................................................................................................ 5

5 Pterostigma length/width ratio 4 (Figure 4 (d)); F11 length/width ratio 2 (Figure 4 (a)) ........................................................................................................................... D. palustris Starý, 1971

- Pterostigma length/width ratio 4.8–5 (Figure 2 (g)); F11 length/width ratio 3.5–3.6 (Figure 1 (c)) ................................................................................................ D. nymphaealis sp. nov.

*Specimens of D. heinzei were not available for analysis; see Mackauer (1959) for a detailed description with figures.