Pechhacker, H. 1976 Zur Vorhersage der Honigtautracht von Physokermes hemicryphus Dalm. (Homoptera, Coccidae) auf der Fichte (Picea excelsa).. Apidologie 7: 209-236.

Notes: [Summary also in French.] Attempt made to develop a useful forecast using first and second instar nymphs.