Remarks on the genera Sphaerotarsus Womersley, 1936 and Hirstiosoma Womersley, 1934 (Acari: Smarididae), with a new distributional record of Hirstiosoma latreillei (Grandjean, 1947) from northern Iran

In this study, we provide a larval stage redefinition of the two genera Hirstiosoma and Sphaerotarsus (Trombidiformes: Smarididae) and new data on the larva of Hirstiosoma latreillei (Grandjean, 1947) collected from the soil and leaf litter of a section of the Hyrcanian forests near the Tilek village, Sari County, Mazandaran Province, Iran. Prior to this study, a single specimen of H. latreillei was collected from Asalem city in Guilan Province, Iran. The considerable distance between the previous sampling site and the collection locality in the present study suggests that H. latreillei is likely distributed not only across the forests of the northern Alborz Mountains in Iran but also in adjacent countries situated between Iran and Europe, such as Türkiye. Furthermore, given the altitudinal range of the collection sites in Gijav village, Asalem city, Guilan Province, and the current study, as well as those reported from European localities, it can be inferred that the occurrence of this species is not altitude–dependent. Collecting the larval host of this species may provide critical insights into its host specificity and broader geographic distribution. A revised version of the identification key to smaridid genera is presented here, incorporating updated definitions for the genera Sphaerotarsus and Hirstiosoma. In addition, a key to the larval species of Hirstiosoma worldwide is provided.