Honeydew found in Nelson Lakes National Park is produced by small beech scale insects called Ultracoelostoma assemile and Ultracoelostoma brittini. They primarily feed on red (Nothofagus fusca) and black (Nothofagus solandri) beech. These insects belong to the same order (Hemiptera) as plant lice or cicadas. Hemiptera includes all insects that feed with suction tubes.
Beech scale insects are found in rutted tree bark where they access the bark's phloem using their suction tubes. The phloem is a bundle of cells that form a layer of living tissue just below the bark. In water dissolved nutrients are transported through this layer which the insects feed on.
The scale insects then convert the nutrients into sugar that is excreted. The sugary droplets (honeydew) then hang from the tree where other insects, the park's nectar-feeding birds, as well as fungi may feed on. Black mould fungi grows rapidly and may cover a tree's bark with a dense black culture.
Deforestation and introduced wasps threaten the beech scale insects today. Once these insects are gone, the entire surrounding ecosystem will be in danger.