The sugarbeet root maggot, Tetanops myopaeformis (Röder) (Diptera: Ulidiidae), survives the winter by undergoing diapause as a matured third-instar larva. Third instars of this insect have been successfully maintained in cold (6±1^oC) storage for up to six years. The energy cost associated with this long-term survival during which there was no food intake, was estimated by comparing the total storage lipid content of field-collected diapausing larvae with matured third-instar larvae maintained in cold storage for one, two, and five years. Gravimetric analysis of total storage lipids from chloroform extracts showed a significant usage of lipids over five years of storage. Lipid usage was low from diapause to one year of cold storage and from two to five years, but increased significantly from one to two years of storage. Analyses by gas chromatography mass spectrometry (GC-MS), and thin layer chromatography (TLC) confirmed that triacylglycerols (TAG) constituted the major class of lipids in both diapausing and stored larvae. The GC-MS data revealed that the major fatty acid from purified TAG in both the test groups was the 16-carbon monounsaturated fatty acid, 9-hexadecenoic acid (16:1). Other prominent fatty acids in order of decreasing abundance were 14:1, 14:0, and 16:0 with lesser amounts of 12:1, 12:0, 18:1, 18:0, 20:1, and 20:0. Quantities of fatty acids from TAG showed a pattern of decrease from diapausing to five-year stored larvae. Relative changes in the percent composition of TAG fatty acids with storage will be presented