Arboridia kakogawana (Matsumura 1932) is a leafhopper species (Hemiptera, Cicadellidae, Typhlocybinae, Erythroneurini), native to the Eastern Palearctic region. It was described from Kakogawa City, Honshu Island, Japan (original combination Zygina kakogawana). Later, its presence was detected also in the Korean Peninsula (Dworakowska 1970), the Russian Far East (Anufriev 1971), and, most recently, in China (Cao et al. 2019).

In the Russian Far East (Primorsky Territory), this species inhabits broadleaved and mixed forests and feeds on Vitis amurensis Rupr. (Anufriev 1971), a plant native to Russian Far East, northern and eastern China, Korea, and Japan (Honshu Island) (POWO 2024); thus, the native range of A. kakogawana and that of its primary host plant coincide.

Its first occurrence in the Western Palaearctic, due to accidental introduction, perhaps via cargo ships (Gnezdilov et al. 2008b), was detected in the Krasnodar area of southern Russia in 1999 (Gnezdilov 2000). Later, its presence was reported from North Caucasus (Balakhnina et al. 2009), Rostov region (Artokhin 2009), Crimean Peninsula (Radionovskaya and Didenko 2014), Ukraine (Martynov et al. 2019), Romania (Chireceanu et al. 2019), Bulgaria (Tomov 2020), Serbia (Šćiban et al. 2021), Moldova (Grozdeva 2022), and Hungary (Schlitt et al. 2024), indicating that its range is rapidly expanding westwards.

Arboridia kakogawana feeds as oligophagous on Vitaceae and has so far been found on Vitis sp. and Parthenocissus quinquefolia (L.) Planch. (Chireceanu et al. 2019). It is reported as a pest of cultivated grapevine both in its native area and in invaded regions of Eastern Europe (Chireceanu et al. 2019). The damage is due to intense trophic activity of nymphs and adults in the leaf mesophyll, consequently affecting grape maturation (Gnezdilov et al. 2008a, 2008b).

This study reports the first data on the occurrence of A. kakogawana in Italy (Piedmont region), which currently represents the western limit of its range in expansion.

The monitoring was conducted on four vineyards; two located in Grugliasco, Turin (we named these two vineyards Agroinnova and Arboricoltura), one in Chieri and one in Montalto Dora (Fig. 1). The area of each vineyard is respectively, 0.37 ha, 0.41 ha, 2.48 ha and 0.05 ha. We installed yellow sticky traps (GLUTOR^®, 40×25 cm, Biogard) horizontally on grape branches. We placed three traps in each of the two vineyards of Grugliasco and the one from Montalto Dora and 24 traps in the vineyard of Chieri, depending on the hectares of each one. Traps were replaced every two weeks. The period of observation went from the end of April to mid-October 2024. We also monitored the vineyards every week to observe the presence of nymphal stages and adults. The specimens we collected by traps were deposited in the Department of Entomology of Grugliasco and then examined through the observation of the aedeagus to identify the species. Some nymphs and adults captured in field were also photographed to observe and describe in detail the morphology.

For the study of genital characters, the entire male abdomens of the examined specimens were dissected out and macerated in 10% KOH solution at approximately 55 °C for about 20 minutes until clarification. The cleared material was subsequently washed in distilled water and transferred to glycerol for observation and further dissection. Finally, the genital pieces were mounted on a slide in dimethyl hydantoin formaldehyde (DMHF) medium.

The drawings of the male genitalia were made by means of a Laboval-4 microscope with drawing tube attachment. The photos of the specimens were taken with SnS-System (MJKZZ, Europe) fitted with a Canon 90D (Canon Inc., Tokyo, Ota, Japan). This system was connected to a computer where the Focus Stacking Studio software (FSS, MJKZZ, Europe) was installed to control the SnS-System.

The image processing and plate composition of the drawings were made by means of MAGIX Xara Photo & Graphic Designer 19.0.1.65946 software. The illustrations are all original.

The morphological terminology follows Dietrich (2005) and Dietrich and Dmitriev (2006).

Arboridia kakogawana is the third exotic typhlocybine species feeding on Vitis introduced in Italy in recent years, after the Nearctic Erasmoneura vulnerata, detected first in 2004 by Duso et al. (2005), and the East-Mediterranean Arboridia adanae (Dlabola 1957), detected first in 2021. These three species have been added to the ampelophagous typhlocybine leafhoppers already occurring in Italy, namely, Hebata vitis (Göthe 1875), Jacobiasca lybica (Bergevin & Zanon, 1922), and Zygina rhamni Ferrari 1882. Although A. kakogawana does not seem to have caused any particular damage in the vineyards, monitoring its range of expansion is recommended.