Fenusa pumila Leach, 1817
Betula pubescens, Hilversum
Betula pubescens, Nunspeet: young mines
Betula pendula, Millingerwaard: oviposition scar
Rather large, clear, partly full depth blotch that begins in the axil of a thick lateral vein. Often the oviposition leaves a greyish-green scar (photo). Generally several mines in a leaf. The mine expands within the confines of the midrib and two lateral veins; only close to the leaf margin, where the lateral veins are thin, the mine may trespass over a vein.
Strong preference for the younger leaves; mines of the later generations therefore at the end of the twigs (Friend, 1931a; Lindquist, 1959a; Cheng & LeRoux, 1965a).
Mines between June and September, in 2-3 generations (Lindquist, 1959a; Cheng & LeRoux, 1965a).
BE recorded (Fauna Europaea, 2008).
NE recorded (van Ooststroom, 1976a).
LUX recorded (Chevin, Ellis & Schneider, 2011a).
distribution within Europe
Entire Europe, with possible exception of the Balkan Peninsula (Fauna Europaea, 2008).
Fenusa pusilla auctorum.
When (as is usual) several mines occur in a leaf, they often develop at quite different speeds. The difference sometimes is quite considerable: sometimes several larvae are full-grown and about to leave their mine, while others seem to have just emerged from the egg. It is not certain (albeit probable) that all mines in a leaf stem from a single ovipositing female. The biological meaning of this differential development is not clear.
Young mines may be confused with mines of Incurvaria pectinea that have not yet made their excisions. The presence of greyish green discoloured oviposition scars then characterizes F. pumila (Buhr, 1941a).
In Europe F. pumila is practically harmless. However, the species has unintentionally been introduced into the United States, and has developed there into a serious forestry pest (Eichhorn & Pschorn-Walcher, 1973a; Smith, 1987a).
Contrary to Fenusella nana, this species mines the youngest, only partly unfolded leaves in the periphery of the crown (DeClerck & Shorthouse, 1985a).
Ahr (1966a), Altenhofer (2003a), Altenhofer, Hellrigl & Mörl (2001a), Beiger (1979a), Beneš & Holuša (2015a), Blank ao (1998a), Buhr (1941a, 1964a), Çalmaşur & Özbek (2004b), Cheng & LeRoux (1965a), Chevin, Ellis & Schneider (2011a), DeClerck & Shorthouse (1985a), Digweed, MacQuarrie, Langor ao (2009a), Eichhorn & Pschorn-Walcher (1973a), van Frankenhuyzen & Houtman (1972a), van Frankenhuyzen Houtman & Kabos (1982a), Friend (1931a), Haase (1942a), Hering (1927b, 1937c, 1956a), Huber (1969a), Kirichenko, Augustin & Kenis (2018a), Kozlov, van Nieukerken, Zverev & Zvereva (2013a), Kvičala (1938a), Lengesova (2008a), Lindquist (1959a), Liston (1993b, 1995b), Lorenz & Kraus (1957a), Maček (1999a), Michalska (1972a, 1976a), Nowakowski (1954a), van Ooststroom (1976a), Pieronek (1962a), Pieronek & Soltyk (1993a), Pschorn-Walcher & Altenhofer (2000a), Ripper (1931a), Robbins (1991a), Savina & Chevin (2012a), Scobiola-Palade (1974a), Skala (1951a), Skala & Zavřel (1945a), Smith (1971a, 1987a), Sønderup (1949a), Stammer (2016a), Taeger, Blank & Liston (2006a), Taeger ao (1998a), Viramo (1969a), Wahlgren (1944a, 1951a, 1963a), Zoerner (1969a, 1970a).