Qualitative and quantitative changes in the neutral lipid content of hemolymph of gypsy moths, Lymantria dispar L., were assayed in larval, pupal, and adult stages. The major neutral lipid constituents of the hemolymph were 1,2-diacylglycerols and ranged in nominal concentration from 1.6–3.4 (larval), 3.1–4.9(pupal),toamaximumof 19.3 μg lipid per microlitre hemolymph in the adult male. When detected, triacylglycerols and monoacylglycerols never exceed diacylglycerol concentrations. The fatty acid composition of 1,2-diacylglycerols from adult male moths (0–12 h after emergence) was determined as fatty acid methyl esters using gas chromatography/mass spectrometry analysis. Nine fatty acid structures have been assigned. Of these, five are saturated, unbranched, aliphatic fatty acids (C14:0 – C18:0) which comprise 80.5% of the total fatty acid abundance. The remaining four fatty acids consist of two saturated, methyl-branched, aliphatic compounds, a mono-unsaturated aliphatic acid, and a tri-unsaturated, tricyclic, diterpenoid acid.