Cold-hardiness of the phoretic mites Anoetus myrmicarum (Acariformes,Anoetidae) from the ants Formica lemani (Hymenoptera,Formicidae) in the Kolyma Highland

In the sparse larch forests of the upper Kolyma River, hypopi of the mite Anoetus myrmicarum (Scheucher, 1957) were found in several nests of the ant Formica lemani Bondroit, 1917. These mites were not found in hundreds of nests of the other 10 ant species examined in northeastern Asia. A possible ecological and physiological conditionality of the restricted distribution of phoretic mites was analyzed. For this purpose, coldhardiness of mites and their ant hosts, the biotopic distribution and the structure of nests, and the temperature conditions of overwintering were examined. At the stage of hypopus, the mites overwintered on ants in the overcooled stage; their mean supercooling temperatures (SCP) varied from ?25.8 ± 0.3°C to ?27.7 ± 0.4°C (min ?32.2°C, n = 157). These values were by 0.1 to 7.0°C lower than the mean SCP of the ants from 8 tested nests of F. lemani (?20.7 ± 0.5°C to ?25.7 ± 0.8°C). The soil temperatures at the level of winter chambers varied from ?12°C to ?15°C. Scarcity of findings of Anoetus myrmicarum in the Kolyma Highland is not associated with the limited cold-hardiness of the examined stages, but is most probably determined by interrelations between mites and ants.