Trichilogaster acaciaelongifoliae (Froggatt) was introduced into South Africa in 1982 for the biological control of Acacia longifolia (Andr.) Willd. (Fabaceae). Since its introduction it has substantially reduced the reproductive potential of this weed and is widely regarded as a successful biological control agent. Nonetheless, with growing concern about the risks of biological control, follow-up monitoring of agents that have been released is strongly advocated. The present contribution examines the geographical range expansion and success of T. acaciaelongifoliae 18 years after its release. This study was carried out at a locality with climatic conditions similar to those that were originally predicted to be unsuitable for T. acaciaelongifoliae.The level of infestation and success of T. acaciaelongifoliae on Acacia floribunda Sieber at the study site in Gauteng Province was found to compare favourably with its performance in the most successful areas of its release. Although climatic matching may be important for the initial establishment of biocontrol agents, in the long-term it is clear that these species are potentially able to expand their geographical ranges. The sex ratio of T. acaciaelongifoliae was strongly female-biased, unlike that previously recorded on A. floribunda. The level of parasitism by a single, newly acquired parasitoid species was unexpectedly high. However, no relationship was found between the fate of T. caciaelongifoliae individuals in galls and gall size. Although this species is an effective biocontrol agent, its long-term behavior (range expansion and association with local natural enemies) has proved to be less predictable.
Concentrations of potential energy substrates were measured in the haemolymph and flight muscles of the dung beetle Pachylomerus femoralis (Kirby). Samples were taken from beetles at rest, captured during flight of unknown length, collected immediately after voluntary termination of flight (without any traces of dung in the vicinity) and collected immediately upon arrival at pats of fresh cattle dung in the Sandveld Nature Reserve, Free State Province, South Africa. Resting beetles had high concentrations of proline in the haemolymph (approximately 145/mol/ml) and flight muscles (approximately 70mol/g) but negligible concentrations of carbohydrates in the haemolymph (lower than 2 mg/ml) and glycogen in the flight muscles (approximately 0.l mol glucose equivalents/g). The beetles that were captured during flight, collected after they had terminated flight voluntarily or were trapped with fresh dung, had substantially lower proline levels in the haemolymph and flight muscles than resting beetles, while alanine levels in both compartments were significantly higher than in resting beetles. There were no differences in carbohydrate levels (in haemolymph and flight muscles) and lipid levels (haemolymph) between resting beetles and those that were active. From these results it was concluded that proline is the only energy substrate for flight in P. femoralis. Sufficient proline was available in the beetles each time it was measured. A lack of fuel is consequently not the reason for beetles to terminate flight.