Review of Hard Ticks (Acari: Ixodida: Ixodidae) in Underground Habitats in Croatia

Between 1993 and 2024, 274 hard ticks (Ixodidae) were collected from 138 underground localities in Croatia. This study represents the most extensive survey of hard tick fauna in Croatian underground habitats to date. The collected hard ticks were classified into three genera and seven species. Ixodes was the most abundant genus, with five species, while Haemaphysalis, and Hyalomma were each represented by one species. The highest number of hard tick species was collected in underground habitats in Dalmatia, followed by north-western Croatia and Slavonia. Ixodes vespertilionis Koch, 1844 was the most abundant species in the collected sample, comprising 81.02%, and was recorded in all studied regions. Only I. vespertilionis was recorded throughout the year, while I. hexagonus was found in nine months, I. frontalis in four months, and the other species in shorter periods. The largest number of I. vespertilionis specimens was collected during the spring months (33.17%), while the fewest were collected in winter (16.58%). The discovery of Ixodes lividus Koch, 1844 in north-western Croatia represents a new country record, increasing the number of hard tick species currently known in Croatia to 28.