Redescription of Pelecorhynchus kroeberi (Lindner), a Patagonian species rediscovered after more than 100 years in Chile (Diptera: Pelecorhynchidae)

Abstract

An adult female of Pelecorhynchus kroeberi (Lindner, 1925) is newly recollected after more than 100 years and it is herein redescribed, including, for the first time, illustrations of genitalia. The specimen was collected in the Región de Aysén, Provincia de Aysén (46°40′11.9″S, 74°00′54.0″W), in the extreme south of Chile, and the specimen is deposited in the Entomological Collection of Museo Nacional de Historia Natural, Santiago, Chile.

Keywords.
Morphology; Taxonomy; Chilean Patagonia.

INTRODUCTION

PelecorhynchusMacquart, 1850 (Diptera: Pelecorhynchidae) is a genus of brachyceran flies, with 40 described species, distributed only in Australia (including Tasmania) and Chile (Daniels, 1989; Llanos et al., 2015). In Chile, the genus comprises nine species, known to occur in the central and southern parts of the country (Llanos et al., 2015; González & Elgueta, 2020).

Pelecorhynchus kroeberi (Lindner, 1925) was originally described as Coenura kroeberi, based on one female specimen from Punta Arenas, collected by R. Pässler in 1908, and deposited in the Entomological Collection of the Zoologisches Museum in Hamburg, Germany (ZMUH). The type specimen was destroyed in 1943 by fire during World War II (Pechuman, 1967), as along with a large part of the dipteran collection of the Hamburg Museum (Weidner, 1969: 228; Bährmann, 1999: 185). In the original description, Lindner did not describe the female genitalia nor provide illustrations of the species.

The present paper aims to redescribes the female of Pelecorhynchus kroeberi based on a specimen collected in southern Chile, providing illustrations of external morphological features and genitalia.

MATERIAL AND METHODS

The specimen was collected in the Región de Aysén, Provincia de Aysén, Chile (46°40′11.9″S, 74°00′54.0″W) (Fig. 1A, B), with a Malaise trap (Fig. 1C). The collecting area corresponds to a subantarctic forest, with a temperate climate of hyper-oceanic influence and dominated by evergreen forests represented by Nothofagus betuloides (Mirb.) Blume and Blechnum magellanicum (Desv.) Mett. Annual precipitation fluctuates between 2,000 and 2,500 mm and average annual temperatures varies from 8 to 9℃, with maximum values of temperature occurring in January (Olivares-Contreras et al., 2019).

Figure 1
(A) Distribution record for P. kroeberi of holotype (circle) and specimen (triangle) in southern Chile. (B) Map showing location of sampling site of P. kroeberi (Lindner) in Laguna San Rafael, Region de Aysén, Chile. (C) Malaise trap that captured P. kroeberi (Lindner).

The morphological terminology for the adult and terminalia follows Cumming & Wood (2017) and Carmo & Santos (2011), respectively. Terminalia was macerated in 10% KOH solution at 50℃ for one hour to soften internal tissues; the solution (with the piece) was then neutralized with acetic acid, rinsed in distilled water, and then dissected in 80% ethanol. Digital photographs were taken with a DS-Fi2 camera mounted on a Nikon trinocular stereomicroscope SMZ 1500. Depth of field was enhanced by Nikon^TD ACT-2U software to stack multiple images into a final image.

RESULTS

Taxonomy

Pelecorhynchus kroeberi ( Lindner, 1925 ) Figs. 1 - 9

Figure 2
Habitus of P. kroeberi (Lindner) female in lateral view. Scale bar = 1.0 mm.

Figure 3
Head of P. kroeberi (Lindner) female in frontal view. Scale bar = 1.0 mm.

Figure 4
Antenna of P. kroeberi (Lindner) female in lateral view. Scale bar = 0.5 mm.

Figure 5
Thorax of P. kroeberi (Lindner) female in dorsal view. Scale bar = 1.0 mm.

Figure 6
Thorax of P. kroeberi (Lindner) female in lateral view. Scale bar = 1.0 mm.

Figure 7
Wing of P. kroeberi (Lindner) female in dorsal view. Scale bar = 1.0 mm.

Figure 8
Abdomen of P. kroeberi (Lindner) female in dorsal view. Scale bar = 1.0 mm.

Figure 9
Terminalia of P. kroeberi (Lindner) female. (A) Terminalia dorsal view. (B) Terminalia ventral view. Abbreviations: cerc: cercus; pvl: posteroventral lobe; spm dt: spermathecal duct; st 8: sternite 8; tg 9: tergite 9. Scale bar = 0.1 mm.

Coenura kroeberiLindner, 1925: 23.

Type locality: Chile, Magallanes, Punta Arenas. Holotype ♀ (ZMUH), destroyed according to Pechuman (1967: 555).

References:Kröber, 1930a: 154 (as Coenura); Kröber, 1930b: 114 (in key), 115; Kröber, 1934: 232 (catalog); Mackerras & Fuller, 1942: 72 (in key, as Pelecorhynchus), 74 (comments); Stuardo, 1946: 67 (catalog); Pechuman, 1967: 555 (comments about holotype); Philip, 1968: 2 (catalog); Pino, 1968: 118 (comments); Pino, 1969: 8 (list); Coscarón & Papavero, 2009: 5 (catalog); Llanos et al., 2015: 198 (redescription); González & Elgueta, 2020: 159 (catalog).

Material examined: 1♀, Chile, Región de Aysén, Provincia de Aysén 46°40′11.9″S, 74°00′54.0″W, 02/December/2021-12/January/2022, R.I. Madriz Coll., Malaise trap, C.R. González Det., Colección Nacional de Insectos, Museo Nacional de Historia Natural, Área de Entomología, Santiago, Chile (MNNC).

Diagnosis: Body color dark-brown. Eyes bare. Frons moderately wide and slightly divergent. Ocellar triangle with three ocelli. Clypeus with brownish pruinescence, laterally with long and dense black hairs. Antennae brownish. Palpus with brown pruinescence, stout, relatively flat, as long as ¼ of the proboscis. Mesonotum dark-brown, with short and dense brown-reddish hairs and a pair of submedial, nearly parallel pale vittae; scutellum dark brown, with long brown hairs on distal margin. Legs mostly brown with short black hairs. Wings hyaline. Abdomen dark-brown dorsally in the background; tergite 1 with a pair of small white-yellowish spots, tergites 2-4 with a pair of circular and broad lateral white-yellowish spots.

Description: Female (length = 21.5 mm; wing length = 16.5). Body color dark-brown (Fig. 2).

Head: Eyes dark-brown, bare, without color pattern. Frons moderately wide and slightly divergent ventraly, with brownish pruinescence and medium black hairs. Vertex with brown pruinescence and short black and brown hairs and few reddish hairs (Fig. 3). Ocellar triangle dark-brown, with short black hairs, three ocelli. Gena with golden-brown pruinescence, and with long brownish and goldish hairs. Clypeus with brownish pruinescence, laterally with long and dense black hairs, medially hairs are shorter and less abundant. Antennal scape brown, with short brownish hairs, pedicel darker. First flagellomere and following three flagellomeres light brown, darker on distal half apically (Fig. 4). Palpus two-segmented with brown pruinescence, stout, relatively flat, as long as ¼ of the proboscis, with long and scarce black hairs (Fig. 3). Proboscis brown, labellum small (Fig. 3). Occiput with light brown pruinescence and black hairs on dorsal edge.

Thorax: Mesonotum dark-brown, with short and dense brown-reddish hairs and a pair of submedial, nearly parallel pale vittae. Postpronotal lobes dark-brown, with long brown-reddish hairs. Scutellum dark brown, with long brown hairs on distal margin (Fig. 5). Pleura coated with gray pruinescence and long yellowish hairs; anepisternum and anepimeron with long yellowish hairs; katepisternum and katepimeron bare (Fig. 6). Legs mostly brown with short black hairs, except for coxa grayish with long yellowish hairs, femur with light brown hairs; tibia concolorous with shorter light brown and black hairs. Wings hyaline, darker on costal and subcostal cells, cell r₅ widely open; veins Sc and R₁ bare (Fig. 7). Basicosta bare. Halter whitish, darker at apex.

Abdomen: Dark-brown dorsally in the background, distal margin of tergites densely covered by brown-reddish hairs; tergite 1 with a pair of small white-yellowish spots, tergites 2-4 with a pair of circular and broad lateral white-yellowish spots, occupying most of the tergite, triangular (Fig. 8). Sternites mostly pale brown, without spots and with scarce brownish hairs.

Terminalia: Cercus two-segmented, apical segment ovoid-shaped (Fig. 9A), and with posteroventral cercal lobes developed curved towards the median plane (Fig. 9B). Tergite 8 squared as long as wide (Fig. 9A). Tergite 9 widely divided, trianguliform. Tergite 10 small. Sternite 8 acuminated (Fig. 9B). Genital fork with a narrow base, neck wide basally and a long spine present on the comb. Three spermathecal ducts, mostly slender.

Distribution: Chile. Región de Aysén, Provincia de Aysén (46°40′11.9″S, 74°00′54.0″W, Western shore of Laguna San Rafael); Región de Magallanes: Provincia de Magallanes (Punta Arenas).

Comments: The genitalia of P. kroeberi is similar to the female genitalia described for other species of Pelecorhynchus (seeMackerras & Fuller, 1942; Nagatomi & Iwata, 1976; Kerr, 2010; Carmo & Santos, 2011), with the basal segment of cercus expanded, forming posteroventral lobe (Carmo & Santos, 2011: 477, Fig. 9A). This character has also been observed in species of Pelecorhynchidae (Glutops Burgess), Rhagionidae (Chrysopilus Macquart, Pseudoerinna Shiraki, Rhagio Fabricius, Symphoromyia Frauenfeld), and Vermileonidae (Vermileo Macquart) (Stuckenberg, 2001; Kerr, 2010). The similarity of the posteroventral lobes in Pelecorhynchus and could be interpreted as a synapomorphy of Rhagionidae + Pelecorhynchus (Pelecorhychidae) (seeSantos, 2006). The shape of sternite 8, with the acuminate anterior margin, is an additional feature supporting Rhagionidae and Pelecorchynchidae as sister groups.

DISCUSSION

Lindner (1925) described Coenura kroeberi based on one female from Punta Arenas, Chile. Later, Mackerras & Fuller (1942: 74) transferred the species of Coenura Bigot to Pelecorhynchus, and stated that “(…) P. kroeberi is similar to P. elegans (Philippi), but differs in that P. kroeberi has white hairs on the pleura, scutellum with distal margin with brown hairs, and legs reddish brown (…)”. Clearly, there are more differences between P. kroeberi and P. elegans. Also, there are many characters by which P. kroeberi can be distinguished from the other South American species of Pelecorhynchus, all of them known only from Chile, as detailed in Table 1.

Pechuman (1967: 555) commented on the morphological similarities between P. kroeberi and his species P. penaiPechuman, 1967, mentioning some differences between both species, such as: “(…) both species have small white spots on the lateral margin of the tergite 1, a character not observed in other species of Pelecorhynchus (…)”. To these differences we added the size (P. kroeberi is longer than P. penai), and color of the pilosity that covers the distal portion of the scutellum (brown in P. kroeberi and golden in P. penai).

Pelecorhynchus kroeberi has been only known from the type locality: “Punta Arenas”. This represents the southernmost Chilean record for a species of Pelecorhynchus. This area corresponds to a vast uninhabited area, primarily inaccessibility, with high biodiversity and endemism (Armesto et al., 1998). The specimen collected on the shore of San Rafael Lake, Province of Aysén, is a record approximately 1,000 km up to the north of the type locality. This is only the second specimen of P. kroeberi found, also a female, and additional collecting effort could contribute to a better understanding of the southern distribution of the species of Pelecorhynchus.

Table 1
Morphological differences between species of Pelecorhynchus from Chilean distribution and P. kroeberi (Lindner).

Characters	P. kroeberi	P. biguttatus (Philippi)	P. elegans (Philippi)	P. hualqui Llanos & González	P. longicauda (Bigot)	P. penai Pechuman	P. toltensis Llanos & González	P. vulpes (Macquart)	P. xanthopleura (Philippi)
Body coloration	Brown	Black	Black	Black	Black	Brown	Black	Reddish-brown	Black
Distal margin of scutellum	With brown hairs	With golden yellow hairs	With brown hairs	With black hairs	With black hairs	With golden hairs	With yellow hairs	With orange-rufous hairs	With black hairs
Pleura	With yellowish hairs	With yellow hairs	With yellowish and golden hairs	With black hairs	With black hairs	With golden hairs	With yellowish hairs	With orange-rufous hairs	With yellow hairs
Wings	Hyaline darker on costal and subcostal cells	Infuscated orange on costal margin	Slightly infuscated orange on costal margin	Infuscated orange	Infuscated orange	Wing hyaline darker along the costal margin	Infuscated orange	Infuscated orange	Infuscated orange
Abdomen	Dark brown dorsally	Black dorsally	Black dorsally	Black dorsally	Shining brown dorsally	Brown dorsally	Black dorsally	Reddish-brown dorsally	Shining black dorsally
T1	With two spots	Without spots	Without spots	Without spots	Without spots	With two spots	Without spots	Without spots	Without spots
Sternites	Without spots	With spots	With spots	With small spots	With spots	Without spots	With spots	Without spots	With spots

ACKNOWLEDGMENTS

We appreciate the help of Dr. R. Isaí Madriz for providing the specimen of P. kroeberi, Dr. Stephen Smith (Biology, University of Waterloo, Canada) for help in editing the English version and for providing helpful comments on the manuscript, and Carolina Reyes for her help with the photographs that accompany this paper.

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• FUNDING INFORMATION:

  The first author is grateful to Dirección de Investigación y Postgrado (DIP), Universidad Metropolitana de Ciencias de la Educación Grant FGI 07 18.
• Published with the financial support of the "Programa de Apoio às Publicações Cientícas Periódicas da USP"

Edited by: Carlos Jose Einicker Lamas

Publication Dates

• Publication in this collection
  09 Dec 2022
• Date of issue
  2022

History

• Received
  07 July 2022
• Accepted
  01 Oct 2022
• Published
  01 Nov 2022