Description of the pupa of Tanytarsus alatus Paggi (1992) (Chironominae: Tanytarsini)

The pupa of Tanytarsus alatus Paggi (1992) is described and figured for the first time. Notes for comparison with other species of the genus are provided, as well as brief notes on its geographic distribution.


Introduction
The species Tanytarsus alatus was described by Paggi (1992) based on the male adult. Later, Sanseverino and Fittkau (2007) transferred this species to the genus Caladomyia after a reinterpretation of the characters of the male genitalia. The genus Caladomyia was erected by Säwedal (1981) based on the posteriorly directed bars on the hypopygial anal point as a synapomorphy. In later works (Reiss 1972, Paggi 1992, Sublette and Sasa 1994, Trivinho Strixino and Strixino 2000, Reiff 2000), more species were described or transfered from the genus Tanytarsus van der Wulp, and after the revision of Trivinho Strixino (2012) the genus comprised 31 species. Recently, Lin et al (2018) analyzed Tanytarsus sensu lato based on the combined analysis of five nuclear markers and concluded that Tanytarsus is paraphyletic with Caladomyia Säwedal placed among South American Tanytarsus, Virgatanytarsus Pinder as part of a Gondwanan clade, and Corynocera Zetterstedt within the Tanytarsus norvegicus (Kieffer) species group. Lin et al (2018) formally synonymized Caladomyia and Virgatanytarsus with Tanytarsus.
In the present study, the pupa of Tanytarsus alatus is described, its taxonomic relationships are discussed in the group of Tanytarsus species with the posteriorly directed bars on the hypopygial anal point, and its geographic distribution is updated.

Material and methods
Collection of a pharate adult, along with several pupal exuviae from the same stream, allowed for life-stage association and description of the pupa of Tanytarsus alatus. A microscope slide for the pharate adult was prepared by clearing the specimen with 10% KOH; neutralization with glacial acetic acid; dehydration in 80%, 96% and 100% ethanol and mounting in Canada Balsam. Pupal exuviae were mounted with the cephalothorax separated from the abdomen and split into two halves along the mid-dorsal ecdysial opening with the outer surface facing upwards. Morphological terminology and measurement standards follow Saether (1980) and Langton (2004); the values are rounded off to the nearest 5 μm unless otherwise stated and measurements are given as ranges. The material is deposited in the collection of the Instituto de Limnología "Dr. Raul A. Ringuelet", Argentina (ILPLA).  Pupal exuviae (n = 6) Color: slightly brownish. Total length 3.83-4.7 (5) mm; cephalothorax length 0.84-1.2 mm (5); abdomen length 2.82-3.5 mm (5).

Discussion
The presence of paired longitudinal bands of long spines on TIII and IV, patches of spinules in the anterior part of TIII-V separated, segments V and VI with 3 taeniate setae, lateral antepronotal setae without spinules, spine bands on TIV nearly parallel or slightly divergent posteriorly fits the description of T. bruneola (Trivinho Strixino) and T. kapilei (Trivinho Strixino) in the key to pupa by Trivinho Strixino (2012). However, those species differ from T. alatus by the possession of a wrinkled frontal apotome and lacking cephalic tubercles, by having patches on T V-VI with short multiple spines, and no anterior paired patches of fine shagreen on T VIII, nor an oval field of fine shagreen on the anal lobe. Sanseverino and Fittkau (2007) described the occurrence of short spines on T IV-VI sitting close to each other or placed on the same base and giving the appearance of multiple spines, a useful character to recognize the previously Caladomyia pupae. The character was not found to be consistent within the genus as several species possess single spinules on T IV-VI. This is also the case for Tanytarsus alatus.
The type locality of Tanytarsus alatus is Embalse Arroyito and the paratypes were collected in Marimenuco, both localities belonging to Neuquen province of Argentina. These localities are in the Monte province of the biogeographic scheme of Cabrera and Willink (1973). This province covers sandy plains, plateaus and low mountain slopes, with a dry and warm climate in its northern portion and dry and cool in the south. Precipitation is scarce with 80 mm per year in the north and 250 mm in the south, and the temperature between 13° and 17°C on annual average respectively. The predominant vegetation type is the xerophilous scrubland or sammophilic or halophilic shrub steppe. The new records presented in this study together with male adults collected in piedmont areas of Tandilia and Ventania mountain hills (both in Buenos Aires province, Argentina) extends the geographic distribution of this species northwards. These localities occur in the Pampean province (Cabrera and Willink 1973) that occupies the plains of eastern Argentina between 31° and 39° south latitude. It extends over horizontal or slightly undulated plains, with some low-rise mountain ranges (up to 1200 m in Ventania Mountain Hills) that emerge as islands. There are slow rivers and numerous lagoons of fresh or brackish water. The climate is warm temperate, with rains throughout the year that decrease from north to south and from east to west (1100 to about 600 mm per year). The average annual temperature ranges between 13° and 17°C. The dominant vegetation is the grass steppe, there are also grasslands, sammophilic steppes, halophilic steppes, marginal forests and various types of hydrophilic vegetation.