The taxonomy and identification of Heliothis armigera and H. punctigera, their distribution and host plants in Australia, the effect of host plant on reproduction and on the development and survival of immature stages, their movements, population biology and dynamics, and their control, are reviewed. Areas where further study is desirable include: the nature of host plant selection and host species preference; adaptability to new cultivars; effects of host plant on development; detailed life-table studies on different host plants; the contribution of predation, parasitism and disease to mortality; factors responsible for fluctuations in populations between years, including the origins of outbreak populations; and control strategies other than insecticide treatment.

Helicoverpa armigera in Australia is found in many different geographic locations and has been recorded on a large number of host plants. We partly investigated the nature of this polyphagy by offering moths from six different sources the same set of host plants in oviposition trials. Laboratory H. armigera ranked the plants offered into the following categories: most preferred-tobacco, maize, sunflower; least preferred-cabbage, pigweed and linseed; intermediate-soybean, cotton and lucerne. Moths reared from field collected larvae showed a similar basic rank order, although there were a number of differences between populations. Further work will be needed to clarify if these small differences represent real geographic variation or simply reflect differences between batches of test plants. Tobacco and sunflower were consistently ranked highly by virtually all populations and, cotton, on which H. armigera is a major pest, was ranked very low. The possibility of exploiting the non- attractiveness of cotton in pest management is discussed.

The role of some plant properties in host plant selection by adults of the polyphagous H. armigera were investigated. Those factors found to positively influence host plant selection included presence of flowers, plant height and application of soil fertiliser. The presence of flowers greatly increased a plant's attractiveness to oviposition. Non-hosts, on which larvae did not survive, were readily oviposited on when offered in flower along with known hosts not in flower. The attractiveness of flowers may provide a mechanism for the expansion of host range. However, no effect of crude plant extracts (including various flowers) on oviposition could be detected. The role of chemical attractants is discussed. Tall plants attracted heavy oviposition and it is suggested that moths use silhouette as a cue to locating plants. There was no effect of plant water status on oviposition.

The effect of various 'herbivore' attributes on oviposition in Helicoverpa armigera were considered in a series of laboratory experiments. Larval diet did not influence the rank order of adult host preference, but early adult experience around a host increased oviposition on that host in subsequent trials. The presence of eggs laid 12 h before did not influence subsequent oviposition on a plant, although newly laid eggs may have. The presence of larvae, larval damage to plants and larval frass reduced oviposition on a plant. These results are discussed in relation to polyphagy in H. armigera.

Experiments were conducted to determine in six cowpea cultivars the modalities of resistance to the cowpea aphid. The resistance modality in IT82D-812 is mainly due to antixenosis, even though reproduction was minimal on this cultivar. Both antixenosis and antibiosis were found to operate in ICV 12, with antibiosis operating in the area of high nymphal mortality and low reproduction. It is suggested that when studying the modality of resistance among crop cultivars, studies of both antixenosis and antibiosis be made in order to determine where the resistance modality lies.