Synorthocladiusfedericoi sp. nov., a new species occurring in the middle basin of the Adige River, northern Italy (Diptera, Chironomidae, Orthocladiinae)

Abstract An adult male Synorthocladius was collected in the middle basin of the Adige River in the city of Verona, northern Italy. A combination of atypical characters for the genus signalled a new species. Synorthocladiusfedericoisp. nov. is here diagnosed and described. The new species is known only from its type locality and is presumed to be a local biogeographical representative of the Italian Pre-Alps. An emended generic diagnosis, a key to known Synorthocladius from Europe and comments on the taxonomic position of the new species are given.

The emended generic diagnosis of the genus given in Cranston et al. (1989) and Liu and Wang (2005) is reviewed and supplemented with some additional characters found in the adult male of the new species.

Material and methods
The studied adult male was collected using a light trap along the banks of the Adige River (altitude = 61 m a.s.l.; 45°26'58.68"N, 10°58'52.81"E), preserved in 80% ethanol and cleared of musculature in 90% lactic acid for about 70 minutes. When clearing was complete, the material was washed in two changes of 50-60% ethanol to ensure that all traces of lactic acid were removed. It was then mounted in polyvinyl lactophenol. Before the final slide mount (dorsal), the hypopygium including tergite IX, the anal point, the gonocoxite and the gonostylus were viewed ventrally and laterally and all morphological details were drawn from all sides. The rest of the abdomen was preserved in 85% ethanol for possible future DNA analysis. Terminology and measurements follow those of Saether (1980) and Langton and Pinder (2007). Taxonomic remarks and comments on the ecology of the new species are provided.

Taxonomy
Genus Synorthocladius Thienemann, 1935: emended generic diagnosis Remarks. The generic diagnosis of Synorthocladius in Thienemann (1935), emended in Cranston et al. (1989) and Liu and Wang (2005), is here supplemented as follows. Head: Frontal tubercles present, circular or triangular; coronal triangle reduced or weakly developed; coronal setae present or absent; sensilla coeloconica on palpomere 3 present or absent. Antenna. Last flagellomere simply clubbed, or with bilobed or truncate apex; antennal ratio between 0.5 and 1.0. Thorax: Acrostichals 0-3, or about 9; scutellum with 2 or 4-6 setae; sensilla chaetica present on tibiae and tarsomeres ta 1 -ta 5 of PI-PII, absent on tarsomeres of PIII. Abdomen: Tergite IX with or without a dorsal hump; anal point slightly to strongly curved upwards. Gonocoxite generally with slender dorsal and ventral inner margin, distinctly broad at base. Virga absent or well developed. Superior volsella flat or broadly swollen. Apex of inferior volsella single or double, long nose-like, lobe-like or truncate, subtriangular or spherical. Gonostylus generally slender to well developed, or atypically globular or bean-shaped as in the new species. The holotype (on one slide and abdomen in one tube) is deposited in the entomological collection of MUSE-Museo delle Scienze, Trento, Italy (Accession number: cINV0017_s61v73).
Etymology. The new species is named 'federicoi' after Federico, the first author's son, who has an inherited passion for insects and contributed to the collection of chironomids with the light trap.

Discussion
The newly described species can be considered as a local biogeographic representative of the Venetian Pre-Alps. Consequently, the description here of S. federicoi sp. nov. increases the total number of valid species of Synorthocladius from Europe to two. Larvae of Synorthocladius species are typically rheobiontic, occurring especially in rheocrene mountain springs and streams fed by groundwater (krenal) (Reiss 1968(Reiss , 1989Evrard 1995;Lindegaard 1995;Lencioni et al. 2011Lencioni et al. , 2012Lencioni et al. , 2018Kettani and Moubayed-Breil 2018;Murray et al. 2018), but also in the rhithral and potamal reaches of rivers with high current velocity (Rossaro 1982). The holotype and only known specimen of the new species was collected in a moderately shaded lotic habitat with sandy to gravely substrate supplied by fresh groundwater, which maintains a low annual variation of temperature. The type locality (Fig. 3) is in the hyporhithral sector of the Adige River (Braioni and Ruffo 1986). It includes stones covered by submerged and emerged bryophytes and microalgae, which provide favourable microhabitats for chironomid larval stages. The environmental data of water recorded in the type locality are: conductivity = 262 µS/cm; pH = 8.4; temperature = 12.5 °C. Emergence of adult chironomids is usually observed in early spring (March-April).
Synorthocladius federicoi sp. nov. is known only from its type locality in the Venetian Pre-Alps (a mountain range of the Italian Alps). It would appear to be a biogeographic representative of lotic habitats delimited by the south-eastern part of the Italian Alps. It is likely to be more widespread in similar lotic habitats or Alpine streams of northern Italy.