The cuticular hydrocarbons ofLocusta migratoria cinerascens-larvae and adults, males and females, gregarious and solitaries-have been investigated by combined gas chromatography-mass spectrometry. The hydrocarbons comprise 52-78% of the cuticular lipids and are divided inton-alkanes (28.7-47.3%), 3-, 4-, and 5-methylalkanes (11.3-15.8%), internally branched monomethylalkanes (13.7-19.9%), and internally branched dimethylalkanes (19.8-35.9%) with seven or nine methylenes between the two branch points. While the sexual dimorphism does not seem to be reflected in the cuticular hydrocarbon composition, clear quantitative variations favoring the longest chain alkanes have been observed between gregarious and solitary locusts, thus revealing a new phase character in these insects.