Disparity of Phoresy in Mesostigmatid Mites upon Their Specific Carrier Ips typographus (Coleoptera: Scolytinae)

SIMPLE SUMMARY: This study investigated the phoretic relationship between mites and one of the most aggressive spruce bark beetles from Eurasia. During one season (April–September), bark beetles Ips typographus were collected with a specific synthetic aggregation pheromone. In the lab, we investigated the diversity of mites associated with I. typographus, mite preferences concerning the body parts of the beetles and how phoretic relationships change during the bark beetle’s flight season. Six phoretic mites species were found and 20% of beetles carried mites. Phoretic mite loads and the percent of beetles with mites were highest during the spring flight period. Phoretic mite species had specific preferences regarding their location on the body of the carrier. ABSTRACT: Ips typographus Linnaeus, 1758, the most important pest of Norway spruce (Picea abies Linnaeus, 1753) from Eurasia has damaged, in the last decades, a large area of forest in Romania. Associations between beetles and their symbiotic fungi are well known compared to beetle-mite relationships. The objectives of the study are to determine: (i) the diversity of mites species associated with I. typographus in a local outbreak from Central Romania; (ii) the mite’s preferences concerning the body parts of their carriers; and (iii) how phoresy changes during seasonal flight activity of the host. A total of 7896 adult I. typographus were analyzed and six mite species (both adults and immature stages) were found: Dendrolaelaps quadrisetus Berlese,1920, Proctolaelaps fiseri Samsinak, 1960, Trichouropoda polytricha Vitzthum, 1923, Histiostoma piceae Scheucher, 1957, Uroobovella ipidis Vitzthum, 1923, and Uroobovella vinicolora Vitzthum, 1926. Most mites were observed under the carriers’ elytra (46.8%), while 26.7% and 25.8% were seen on the thorax and elytral declivities, respectively. Mite phoresy peaked in the spring corresponding to the dispersal flight of the carrier. A smaller peak in phoresy occurred in the summer during the second beetle generation.