Cold hardiness of the arctic ensign scale Arctorthezia cataphracta (Homoptera, Ortheziidae) in the Northeast of Asia

Abstract

Cold hardiness of the Arctic ensign scale Arctorthezia cataphracta, which is widely distributed in the Holarctic and penetrates farther north than any other scale insect up to zonal tundra, was studied in the upper Kolyma River basin. Similar to other representatives of the suborder, A. cataphracta overwinters at different developmental stages, which does not require completion of the life cycle during one warm season and reduces its dependence on the amount of heat during summer. Similar to the other scale insects studied, A. cataphracta cannot survive soft tissue freezing and overwinters in the supercooled state. The mean supercooling point equals–32°C, the lowest tolerable temperature under long-term exposure is about–25°C, and the content of antifreeze polyols is up to 7%. These characteristics are closer to those of some boreal scale insects, whose northern distribution boundaries lie much farther south. The successful expansion of this species to the north is facilitated by its feeding on fungal hyphae and overwintering in the microhabitats sheltered beneath the vegetation cover and snow.