Populations of African black beetle, Heteronychus arator (Fabricius), a subterranean pasture-dwelling pest of potatoes, were examined in pastures in geographically separated potato-growing areas covering 3½° of latitude in southwestern Australia. Abundance of all life stages was estimated by taking soil cores and the reproductive state of females was assessed from the stage of their ovarian development. H. arator adults emerged in late summer-early autumn (January–March), ovaries matured slowly during winter and oviposition occurred in spring (September–November). The interval between equivalent population events was about six weeks from the northernmost to the southernmost regions. Fecundity was estimated to be around 12 eggs/female and greatest natural mortality occurred late in the pre-adult development phase.

The stages of bush fly Musca vetustissima Walker, killed by the dung beetles, Onthophagus binodis Thunberg and Onitis alexis Klug, at low and high densities were measured in cattle dung of low nutritive value. A high level of M. vetustissima mortality occurred in the presence of Onitis alexis and Onthophagus binodis in experiments both in the laboratory at a constant 25°C, and exposed to summer fluctuating temperatures outside. The K values for total eggpuparia mortality increased curvilinearly with increasing log10 beetle numbers. The mortality of older larvae, k3, was most closely correlated with total mortality, K, where b = 0.720 and r2 = 0.931, while a lesser but significant correlation was obtained with mortality of young larvae, k2, where b = 0.291 and r2 = 0.645, but no correlation was obtained with egg mortality, k1, where b = −0.010 and r2 = 0.058. It is predicted that in unfavourable dung which occurs during summer, mortality of older bush fly larvae will be the key mortality caused by scarabaeine dung beetles.

The foraging behaviour of the redlegged earth mite, Halotydeus destructor (Tucker), in annual pasture was documented and the relative numbers of individuals foraging on subterranean clover, Trifolium subterraneum (Leguminosae), capeweed, Arctotheca calendula (Compositae) and grasses (mainly Lolium rigidum (Gramineae)), estimated in winter and spring in south-western Australia. The main feature of H. destructor foraging behaviour was the presence of aggregations ranging in size from 3–36 individuals on the adaxial surfaces of the upper canopy of the pasture. Most aggregating individuals were feeding, while most solitary and paired individuals were searching. There was no evidence that individuals aggregated for reproductive behaviour; the adult sex ratio was similar to that of the population even though immatures were under-represented in aggregations. During winter the distribution of numbers of H. destructor on subclover, capeweed and grasses in the upper canopy of pasture was similar to the estimated ground cover of these plant species. However, individuals showed host-plant selection for subclover when feeding. During spring, when the pasture plants were flowering, there were more H. destructor in capeweed flowers than in aggregations on subclover foliage. The capeweed flowers were shown to enhance the rate of H. destructor reproduction in a laboratory experiment. Most H. destructor were on or near the soil surface, with 10% at any one time on the upper canopy of the pasture. H. destructor is polyphagous, and behaved in pasture as a selective opportunist feeder.

Resistance involving penetrability of cotyledons of subterranean clover Trifolium subterraneum (Leguminosae) by the redlegged earth mite, Halotydeus destructor Tucker, was examined in this study using several approaches. Values of penetrability, presented as mechanical strength measured with a penetrometer with a tubulated probe, of cotyledons tested 11–13 days after seeding, from nine varieties of two subspecies of subterranean clover (T. subterraneum subsp. yanninicum and subsp. brachycalicinum) were negatively correlated with feeding damage caused by H. destructor in both 3 h pairwise choice tests in a Petri dish with detached cotyledons, and in 2 week multiple choice tests in containers with seedlings. Simulation tests with different artificial membranes (Parafilm and Gladwrap) making up sachets, containing 5% glucose as a feeding stimulant, indicated that within 3 h H. destructor preferred membranes with lower strength. Field-collected young adults had significantly higher physical fitness to feed and/or gather on the artificial membrane sachet containing 5% glucose, than those from the laboratory culture, when the sachet was compared with cotyledons of either resistant (DGI007) or susceptible (Dalkeith) varieties in the choice tests. Electron microscopic observations of mite infested cotyledons of the resistant variety (DGI007) reveal that upper epidermal cell walls around penetration holes are bent inwards. Anticlinal cell walls of palisade cells appear buckled following attack by H. destructor. The results from these studies were taken as further evidence for the involvement of mechanical factors in antixenotic resistance of subterranean clover cotyledons to H. destructor.

Laboratory bioassays and field trials were used to characterize resistance to three aphid species (Myzus persicae (Sulzer), Acyrthosiphon kondoi Shinji, Aphis craccivora (Koch) in two aphid-resistant varieties (Kalya, Tanjil) and one susceptible variety (Tallerack) of Lupinus angustifolius L., and in one resistant variety (Teo) and one susceptible variety (Wodjil) of L. luteus L. Host selection tests in the glasshouse showed that alates of all three species preferred L. luteus to L. angustifolius, but provided no evidence that alates selected susceptible varieties over resistant. These results were supported by a field trial, which showed no difference in the number of colonizing A. kondoi alates collected from the resistant and susceptible lines of each lupin species, but there were significantly more late-instar nymphs and apterous adults on the susceptible lines. In laboratory host suitability experiments, there was much greater suppression of aphid growth and survival on Teo than on Kalya and Tanjil. In field trials, the numbers of aphids were generally lower on resistant compared to susceptible lines of both lupin species with one notable exception: M. persicae numbers were not lower on the resistant variety Tanjil compared to the susceptible variety Tallerack (L. angustifolius). These results suggest that the resistance mechanisms in both lupin species do not affect the selection of hosts by colonizing aphids, but rather are affecting the growth, survival and possibly reproduction of aphids after settling.