Progomphus joergenseni Ris, 1908

Molineri, Carlos, Rodríguez, José Sebastián, Leiva, Marta & Márquez, Javier Andrés, 2023, Diagnoses and key for the larvae of Progomphus Selys, 1854 from Argentina (Anisoptera: Gomphidae), with first larval descriptions for P. aberrans Belle, 1973 and P. kimminsi Belle, 1973, Zootaxa 5297 (2), pp. 239-259 : 246-249

Progomphus joergenseni Ris, 1908 ( Figs. 5–6 )

Material. ARGENTINA: 2 larvae (IBN-O-107) from Tucumán, J.B. Alberdi, Escaba de Abajo, río Singuil , 27.76516° S, 65.79780° W, 900 m, 12/Nov/1999, C. Nieto leg. ; 18 larvae (in 3 vials: IBN-O-109, IBN-O-110, IBN-O-114) from Catamarca, Santa María, Famabalasto, río Santa María , 26.83594° S, 66.30061° W, 2220 m, 19/May/2007, C. Molineri et al. leg .; 1 larva (IBN-O-111) from Catamarca, Santa María, Corral Viejo, río Santa María , 26.98601° S, 66.26516° W, 2191 m, 4/Oct/2005, C. Molineri leg. ; 8 larvae (IBN-O-112) from Catamarca, Santa María, Saladillo ( Punta Balasto ), río Santa María , 26.9883° S, 66.26202° W, 2188 m, 5/Sep/2011, F. Romero leg. ; 9 larvae (IBN-O-115) from Catamarca, Santa María, ca. Famabalasto, río Santa María , 26.83594° S, 66.30061° W, 2220 m, 19/ May/2007, C. Molineri et al. leg .; 1 male from San Luis, río Lujan, Lujan , 32.39361 S, 65.91500 W, 647 m, 10/ Feb/2017, Márquez leg. BOLIVIA: 3 larvae (IBN-O-113) from Tarija, Arce, La Mamora, río Orosa , 22.20256° S, 64.62683° W, 1100 m, 5/Oct/2004, C. Molineri & V. Manzo leg.

Larval diagnosis. Progomphus joergenseni can be distinguished at larval stage from other species in the genus by the following combination of characters: fourth antennomere reduced, knob-like ( Fig. 6a ); mandibular formula ( Figs. 5a–b ): L 1234 0 a (m 1,2,3,4) b, R 1234 y a (m1) b; galeolacinia with 4 ventral teeth, the first (basal) one about 2/3 length of the second ( Fig. 5c ), basal area of galeolacinia with a tuft of long setae, palp slightly crenulated on inner margin ( Fig. 5c–d ); prementum subrectangular ( Fig. 5e ), ligula with a pair of contiguous submedian tubercles, margin with two rows of flat setae, subrectangular on ventral row, longer and more acute in the dorsal row ( Fig. 5f–g ); lateral margins of prementum with about 10 spines ( Fig. 5e ); labial palp with smooth margins, inner apical projection subtriangular reaching basal 1/3 of movable hook, movable hook stout slightly shorter to outer palpal margin; tarsal claws not cheliform, normal (long and acutely pointed, flattened), hind claw without a subapical seta; thorax and legs with whitish setae; pro- and mesotibia with distal spurs; hind tarsi darker than the rest of the leg; posterolateral spines present on S6–9 ( Fig. 6c ); acute dorsal tubercles present on terga S2–9 ( Fig. 6b ); sterna S2–9 formed by three plates, sterna S1 and S10 formed by one plate ( Fig. 6c ); apical abdominal segments and anal pyramid stout, relative length of sterna S8: S9: S10: epiproct = 1.4: 1.3: 1: 1.3.

The larva of this species was described by Muzón & Lozano (2011), and was associated with the adult stage by supposition (it is the only species occurring in the area studied by these authors). We did not rear specimens from larva to adult; identifications of larvae were done following the above mentioned description. Differences between our material and the original larval description include the presence of molar crest with 1 small denticle in right mandible, while in the original description, only denticles a and b are present (i.e., m denticles are absent). More studies are needed to resolve if this difference is due to wear and tear of the mouthparts in the larvae described by Muzón & Lozano (2011), or to geographical differences. Another important difference is the size of dorsal tubercles or “hooks”, in our material they are large and decreasing in size rearward, but in Muzón & Lozano (2011) dorsal hooks on segments 2–3 are much larger than the others. We do not think that our larvae represent another species, because the adults collected in the localities listed above are typical P. joergenseni . Additionally, in most of the localities listed under material sections, it was the only species of Progomphus present.

Among the Argentinean species, P. joergenseni is similar to P. phyllochromus and P. lepidus because both present last antennomere short and spherical, distal spurs on pro- and mesotibiae, and abdominal posterolateral spines present on S6–9. Nevertheless, P. joergenseni can be readily separated from them by the abdominal sternum of S8 formed by three plates (formed by five plates in the other two species).

Distribution. Peru, Bolivia, Chile, Argentina (Catamarca, Córdoba, La Rioja, Mendoza, Neuquén, Río Negro, Salta, San Juan, Tucumán, and a new provincial record for San Luis) ( Belle 1973; Lozano et al. 2020).

Figures

FIGURE 5. P. joergenseni Ris, last instar larval exuvia: a, left mandible, occlusal view; b, right mandible, occlusal view; c, maxilla, ventral view (arrow indicates first tooth); d, same, dorsal view; e, prementum, dorsal view; f, detail of thin setae on ligula, ventral view; g, detail of flat marginal setae and tubercles, ventral view.

FIGURE 6. P. joergenseni Ris, last instar larval exuvia: a, dorsal habitus (antennomeres are numbered, ts=tibial spur); b, abdomen, lateral; c, abdomen, ventral.