Biodiversity in your home and beyond is a wonderful thing, says Carita Lindstedt-Kareksela of the University of Helsinki (Carita Lindstedt-Kareksela).

At Christmas, many Finnish homes are visited by both Father Christmas and extended family members. Some unexpected guests also arrive with the Christmas tree. Carita Lindstedt-Kareksela, Associate Professor of Forest Entomology at the University of Helsinki and a Research Fellow at the Academy of Finland, estimates that a single Christmas tree can be home to as many as several thousand living creatures.

Forest entomology is the study of insects living in forests.

Among the species that may arrive in your home with the tree, K. Lindstedt-Kareksela first mentions small spiders that spend the winter in young spruce stands. At room temperature, they can become active quite quickly. Insects that overwinter in spruce trees are found among the needles, on the trunk, or in the cones. A fairly common species is the grey carpet (Thera variata), whose larvae spend the winter among the needles.

Another species, although somewhat rarer, that can be found among spruce branches is Calliteara abietis. In Finland, it is mainly found in the south of the country. Immature forms of Sacchiphantes abietis insects can be found at the base of spruce buds. If the tree is mature enough to produce cones, you may find Dioryctria abietella in it.