Silent invaders: New insights into the spread of Trichoferus campestris and Xylotrechus stebbingi and first continental European record of Callergates gaillardoti (Coleoptera: Cerambycidae)

Human activities have provided many opportunities for the introduction and spread of non-native species worldwide. Among these, the longhorn beetles (Cerambycidae) are particularly successful because of their adaptability, concealed lifestyle, and association with the global trade of wood and plant products. Here we report new faunistic data on three cerambycid species from Bulgaria. The alien longhorn beetle Trichoferus campestris (Faldermann, 1835), native to East Asia and already established across numerous European countries, is reported for the first time in Bulgaria. Callergates gaillardoti (Chevrolat, 1854), native to the Eastern Mediterranean, is also recorded for the first time in the country, marking its first record in continental Europe. New data on the distribution of the Sino-Himalayan Xylotrechus stebbingi Gahan, 1906 are provided, representing the second confirmed occurrence of the species in Bulgaria and expanding its known range since its initial discovery in 2019. The single record of C. gaillardoti most likely represents an accidental introduction through the trade in timber or other goods. It is unlikely that the species has managed to establish a population following this interception. On the other hand, both T. campestris and X. stebbingi have managed to establish populations in multiple localities across the country. They are considered potentially harmful, as they can infest healthy trees and damage urban greenery and timber, with the former already included on the EPPO A2 quarantine pest action list. However, there is currently insufficient evidence to classify either species as invasive in the country. In this regard, we propose appropriate methods for monitoring and detecting these species that consider their nocturnal biology. This study is a part of the project under Grant contract number KP-06-N61/6 – 14.12.2022, funded by the National Science Fund of Bulgaria.