Secretions of stingless bees: the Dufour glands of some Frieseomelitta species (Apidae, Meliponinae) Eda Flávia L.R.A. Patricio, Leopoldo Cruz López, Roland Maile and E. David Morgan Apidologie, 34 4 (2003) 359-365 DOI: 10.1051/apido:2003027