Pseudacteon notocaudatus, Plowes, Robert M., Folgarait, Patricia J. & Gilbert, Lawrence E., 2015

Plowes, Robert M., Folgarait, Patricia J. & Gilbert, Lawrence E., 2015, Pseudacteon notocaudatus and Pseudacteon obtusitus (Diptera: Phoridae), two new species of fire ant parasitoids from South America, Zootaxa 4032 (2), pp. 215-220 : 215-217

Pseudacteon notocaudatus new species

Fig. 1

Pseudacteon sp. near disneyi, Calcaterra et al. 2005 Pseudacteon disneyi (in part), Patrock et al. 2009

Diagnosis. Females: most similar to P. pradei ( Fig. 2 ), but P. notocaudatus differs in having the terminal (posterior) segment of the oviscape with a distinct constriction (notch) ahead of the broadened arc on the apical structure, while P. pradei lacks such constriction ( Figs. 1 & 2 ). Both P. notocaudatus and P. pradei have two short lateral points on the apical structure, and this feature differs from the similar species P. disneyi Pesquero 2000 ( Fig. 3 ) and P. arcuatus Borgmeier 1969 ( Fig. 4 ) that both have longer, wider lateral expansions of the apical structure. Males: unknown.

Female. Body length including oviscape 0.95 mm (paratype range 0.88–1.01 mm), thorax width 0.41 mm (paratype range 0.33–0.42 mm). Wing length 1.10 mm, width 0.48 mm. Body color dark grey brown, frons dark grey. Palpus pale yellow. Flagellomere 1 orange brown, flattened in cross section, conical with distal half forming a tapered tip, microscopically pubescent, tapered tip with lateral fringes of longer setae. Arista absent. Frons with 2-2-4-4 setae and 1 pair of supra-antennal setae. Scutellum with 2 pairs of setae, posterior pair over twice the length of fine anterior pair. Costa with 12 pairs of short 0.03 mm setae. Halter light brown, cream below. Legs pale yellowish brown.

Abdomen: Tergite 6 light grey with 3 bristles on each darker lateral patch. Sternite 6 chitinized dark brown, with 2 pairs of long (0.12 mm) medial setae and 3 shorter (0.06 mm) lateral setae on each side. Oviscape comprises two parts. Anterior portion (0.3 mm long) somewhat triangular in dorsal view, spreading from a narrow proximal base (0.06 mm wide) and terminating distally with inwardly curving, hooked lobes on each side (0.19 mm wide). Two fine setae on each side of outer dorsal face. Posterior apical structure (0.12 mm long) extending beyond anterior process, flat in lateral view, broadens in dorsal view from attachment point (0.04 mm wide) until about twice width (0.08 mm), then has a constriction or "notch" (0.06 mm wide), before broadening again and terminating in a curved expansion with short, sharp lateral tips (0.115 mm tip to tip). In lateral view, the apical structure lies at an obtuse upward angle compared to the anterior portion of the oviscape.

Distribution. Found in Tucuman and Salta provinces of northwestern Argentina. Records of P. pradei and P. disneyi from Bolivia and nearby regions of Brazil ( Patrock et al. 2009) may be of this new species.

Etymology. The species name means “notched tail” in Latin, so named for the distinctive constriction of the apical process of the oviscape.

Holotype. ♀, ARGENTINA: TUCUMAN: Graneros, 27.651º S, 65.464º W, 15.v.2012, G.A. Montenegro, over S. invicta nest, BFL- 110564 ( MACN).

Paratypes. ARGENTINA: TUCUMAN: Graneros, 27.651º S, 65.464º W, 3♀, 15.v.2012, G.A. Montenegro, over S. invicta nest ( UTIC); Los Sueldos, 27.112º S, 65.276º W, 1♀, 1.iv.2010, G.A. Montenegro, over S. invicta nest (PJF); SALTA: Bella Vista, 27.752º S, 65.950º W, 2♀, 15.i.2011, G.A. Montenegro, over S. interrupta nest ( UTIC); El Carancho, 25.831 º S, 64.996 º W, 1♀, 1.vii.2011, G.A. Montenegro, over S. interrupta nest ( UTIC); La Palata, 25.750 º S, 64.950 º W, 1♀, 1.i.2011, G.A. Montenegro, over S. interrupta nest ( LACM); Palo Quemado, 26.110º S, 65.269º W, 1♀ ( UTIC), 27.iii.2013, G.A. Montenegro, over S. interrupta nest ( UTIC).

Remarks. Found attacking Solenopsis invicta and S. interrupta workers at disturbed mounds, especially on workers that were active on low grass and sticks close to the place of disturbance. Has not been found at foraging trails.

The distinctive notch on the apical structure of the oviscape serves to differentiate this new species from closely related congeners, especially P. pradei . Separation of these species in the field using a hand lens would be difficult given their extremely small size. However, the morphological differences are stable within species. The geographical ranges of each species appear to be non-overlapping but are still to be fully explored, and we speculate that they may be associated with range limits of host ant species.

Figures

FIGURES 1 – 2. Oviscapes, dorsal-ventral view: (1) Pseudacteon notocaudatus new species. Holotype. (2) Pseudacteon pradei Borgmeier. Specimen from Bom Jardim, Rio de Janeiro, Brazil, O. Bailez, 18. viii. 2012 (UTIC). For clarity of illustration the upper and lower processes are each shown in a perpendicular dorsal view, although in practice they lie in slightly different planes. Scale bar 0.1 mm.

FIGURES 3 – 4. Oviscapes, dorsal-ventral view: (3) Pseudacteon disneyi Pesquero. Outline sketch based on illustration in Pesquero 2000. (4) Pseudacteon arcuatus Borgmeier. Outline sketch based on illustration in Plowes et al. 2009. Scale bar 0.1 mm.