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.

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.

Helicoverpa armigera (Hiibner) and H. punctigera (Wallengren) are major pests of cotton and other field crops in Australia. Using data on the abundance of males in pheromone traps at many sites over three seasons, the spatial and temporal variation in trap catch of both species were examined using Taylor's power law and spatial autocorrelation. The distribution of both species was highly clumped, both temporally and spatially. Regression coefficients for the relationship of spatial mean to variance (b s ) were similar to those for noctuids in general, while similarly derived temporal values (£> t ) for H. armigera fell towards the upper end of the noctuid range and those for H. punctigera well above the range given by . Taylor and colleagues suggested that patterns of dispersion are speciesspecific and that they reflect density-dependent patterns of movement towards and away from centres of abundance. Although the relationship between variance and mean abundance for both spatial and temporal aspects of trap catches of Helicoverpa is well fitted by Taylor's power law, it is argued that these patterns of dispersion are a consequence of demographic and environmental stochasticity. Little need is seen to invoke specific densitydependent behaviours as the major factor responsible in this case. In addition, while Taylor's power law indicated both species had a similar clumped distribution, limited autocorrelation analysis suggested a random dispersion of pheromone-trap catches for H. armigera and small scale patchiness (over distances of 1-2 km) in trap catches of H. punctigera.

Summary Invertebrate predators and parasitoids have long been characterized as having a hyperbolic (Type 2) functional response. Modifications were made to Holling's sand paper disc experiment which consisted of limiting the initial period of search during which a host must be contacted. Failure to contact a host during this initial period causes the predator to emigrate from the search area. The modification generated a sigmoid (Type 3) functional response. This response resulted from the low probability of encountering a host during the initial period of search at low host densities in the time allotted. A limited period of search has been found in several insect parasitoids. Such a strategy would minimize the time (energy) spent per offspring produced by minimizing the time invested in searching microhabitats in which hosts are scarce or absent.

The number of larval instars of Helioihis arnii,pon ((Hiibner) varied from five to seven when larvae were reared at :I constant temperature on an artificial diet. Five or six instars were characteristic of larvae from a second generation laboratory culture, whereas six or seven inst;irs occurred in those from a fifth generation culture. The number of instars was determined by nmisuring the widths of larval head capsules and the mean widths were compared with those obtained from samples of field collected larvae.