The levels of lipophorin, the principal insect haemolymph lipoprotein, were estimated during the development of solitary and gregarious phases of Schistocerca gregaria using single radial immunodiffusion. In the gregarious phase, lipophorin titres ranged from 6.69 ± 0.57 mg/ml in the 3rd nymphal instar to 14.42 ± 2.04 mg/ml in mature adults. The titres in the solitary phase were 3.33 ± 0.59 mg/ml in the 3rd nymphal instar and 8.44 ± 0.67 mg/ml in mature adults. Peak lipophorin titres occurred in mature adults (14.42 ± 2.04 mg/ml) and 5th nymphal instar (8.75 ± 0.25 mg/ml) for gregarious and solitary locusts, respectively. Gregarious locusts had significantly (P< 0.05) higher lipophorin titres than their solitary counterparts during the 3rd and 4th nymphal instars as well as in the adult stage (P< 0.01). Estimation of the haemolymph protein levels over the same period showed a general increase from the 3rd nymphal instar to mature adult stage in both phases. It is proposed that the higher lipophorin titre in gregarious locusts is a physiological adaptation that ensures high lipid reserves that are necessary to cope with the high metabolic requirements of this phase.

Lipophorin was isolated from the stalk borer, Busseolafusca, larvae by ultracentrifugation in a KBr density-gradient. The lipophorin (M, ˜ 700,000) is a high density lipoprotein (density = 1.13 g/ml) composed of 46% lipids and 4% carbohydrates. It consists of two apoproteins, apolipophorin-I (apo Lp-I, Mr ˜210,000) and apolipophorin-II (apo Lp-II, Mr ˜78,000). Both apoproteins are glycosylated as shown by periodate Schiff reagent staining and binding to the lectin, concanavalin A. Amino acid composition analysis of lipophorin showed predominance of aspartate (13%), glutamate (9%) and glycine (9%).

In an immunoblotting experiment, both apoproteins showed immunoreactivity with antiserum to B, fusca lipophorin and no cross-reactivity occurred with any other haemolvmph proteins. Immunodiffusion studies with the same antibodies showed cross-reactivity with haemolymph derived from other Lepidoptera and not from Orthoptera, Dictyoptera or Diptera.