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•Behavioral resistance is often claimed but rarely supported upon close scrutiny.•Most cases represent some form of general behavioral avoidance to the insecticide formulation or aversion response to its effects not a de novoselected response.•The best examples of behavioral resistance show a change in receptor responses that are under genetic control and have been selected similar to classic insecticide resistance.

The spatial pattern of outbreaks of pink wax scale, Ceroplastes rubens Maskell, within and among umbrella trees, Schefflera actinophylla (Endl.), in southeastern Queensland was investigated. Pink wax scale was common on S. actinophylla, with approximately 84% of trees positive for scale and 14% of bees recording outbreak densities exceeding 0.4 adults per leaflet. Highly aggregated distributions of C. rubens occur within and among umbrella trees. Clumped distributions within trees appear to result from variable birth and death rates and limited movement of first instar crawlers. The patchy distribution of pink wax scale among trees is probably a consequence of variation in dispersal success of scale, host and environmental suitability for establishment and rates of biological control. Pink wax scale was more prevalent on trees in roadside positions and in exposed situations, indicating that such trees are more suitable and/or susceptible to scale colonisation.

Using a tethered-insect technique, we investigated within- and between-population variation in the post-alighting host-plant preference and specificity of female Helicoverpa armigera from four populations. No significant difference occurred among populations in host-plant preference. Differences in host-plant preference existed among female moths within a population, and these differences are under genetic control and heritable. Most females ranked maize, sorghum and tobacco highest, followed by cotton varieties DP90 and HG660. The least-preferred plants were cowpea and lucerne. A few females (20%) differed from this general pattern and among each other, and reversed the rank order of host plants. Within a population, individual female moths differed in their host-plant specificity, with some individuals being more generalist than others. Similarly, significant differences occurred in host-plant specificity among populations. The relevance of these findings are discussed in relation to polyphagy in H. armigera.

Extensive surveys during the winter months in inland areas of Australia have greatly extended both the range and known hosts of Australia's two pest Helicoverpa species. H. punctigera was the more common species, being collected from c. half of the sites sampled. Here a further 47 plant species in 8 families are recorded as possible host plants; the majority (all except two) are new records of native hosts, and greatly extend the existing lists. H. armigera was less common, being recorded from c. 10% of the 554 sites sampled. This species was reared from 28 species in 10 plant families. Both moth species are recorded for the first time from various native plant species, predominantly in the Asteraceae and Fabaceae. The Goodeniaceae is also added to the host list of both species. Determination of the status of host plants is discussed.

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.

C. plebejana were reared from egg to adult at a range of constant temperatures. At 10-degrees-C no immature stages survived. Development rates increased over the temperature range 14-34-degrees-C; these were simulated with a non-linear model. Females emerged before males. Fecundity decreased with increased rearing temperature as a direct result of reduced adult female weight. At 34-degrees-C development rate and survival were reduced and all eggs laid were infertile. Optimum temperature for population increase was 28-degrees-C. Validation of a non-linear model for development rate shows that the species of host-plant affects mean development rates of tipworm. Although 5.3 tipworm generations are possible on cotton annually, only one occurs; reasons for this are suggested.

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.

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.

Oviposition behaviour of female Euploea core butterflies, a polyphagous species, was examined in the field and the laboratory. In the field females oviposited eggs singly on Nerium oleander and Parsonsia straminea. On N. oleander most eggs were laid on flowers and very young leaves. On P. straminea (none of which were flowering) very young leaves were favoured. In both species most eggs were laid on the undersurface of plant structures. Eggs tended to be located in the upper portions of plants, which reflects the general distribution of young foliage and flowers. This was more pronounced in N. oleander (a bush) than P. straminea (a vine). The distribution of eggs among both species was clumped. Height of N. oleander plants appeared to have no effect on oviposition, and neither did the distribution of plants. N. oleander plants in the shade were favoured above those in exposed positions. Plants of pink-, white- or red-flowered varieties were equally likely to be used. In the laboratory females oviposited on all plants offered from the families Asclepiadaceae, Apocynaceae and Moraceae, with N. oleander and P. straminea receiving many eggs. Asclepias species were sometimes highly favoured for oviposition, although these species are not suitable for larval development. No evidence was found for the prior presence or absence of eggs on plants influencing subsequent oviposition, nor was any evidence found for a marking pheromone influencing oviposition.

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.