Whole-mounted Malpighian tubules of larvae from two meliponid bee species fixed in acetic acid-ethanol showed a positive cytoplasmic staining with Schiff reagent when submitted to the Feulgen reaction in which acid hydrolysis was done in 4 M HCl at room temperature. The ability of various treatments applied before the Feulgen acid hydrolysis to abolish this cytoplasmic staining was examined. The aldehyde groups of phospholipids present in the cytoplasm of the Malpighian tubules were blocked or removed by sequential treatment with 5% sodium borohydride and acetonechloroform (1:1, v/v) for 15 min each prior to HCl hydrolysis. This treatment is recommended in order to abolish the cytoplasmic (plasmal) reaction and to allow the reliable quantification of DNA by the Feulgen reaction and the discrimination of nuclear phenotypes in the Malpighian tubules of meliponid bees.