Apolipophorin-III (apoLp-III) is present at relatively high levels in the antenna of the male red imported fire ant, Solenopsis invicta (Formicidae: Hymenoptera). PCR analysis shows that apoLp-III is expressed in the male antenna as well as in other male body segments, and it is also expressed in workers. ApoLp-III is known to be involved in transport of diacylglycerol through the hemolymph from fat body to flight muscle in locusts. However, male fire ants do not have a high fat content and probably do not use fat as a major fuel for flight. Additional known functions for apoLp-III include immune response and apoptosis, and lipophorins also carry cuticular hydrocarbons and pheromones in some insects. Therefore, we are investigating whether apoLp-III might have an olfactory function in fire ants. We expressed fire ant apoLp-III in E. coli and the purified recombinant protein was found to be functional in binding to hydrophobic ligands. ANS binds to fire ant apoLp-III with a dissociation constant in the micromolar range, similar to ANS binding to intracellular lipid-binding proteins. Fire ant apoLp-III also binds phospholipid vesicles, as detected by diminished light scattering and formation of small rods observed by negative stain transmission electron microscopy. We are currently testing the capacity of fire ant apoLp-III to bind endogenous ligands.