Female Musca vetustissima Wlk. may be allocated to one of seventeen classes of development between emergence and the start of the fourth ovarian cycle, the criteria being the amount of pupal fat body, but chiefly the presence and size of the follicular relics (yellow bodies and beads in the ovaries) during successive ovarian cycles. The duration of these cycles was estimated under standard and differing environmental conditions. Withholding protein for up to two weeks merely delayed the first ovarian cycle, but longer deprivation caused reduced fertility. The initial phase of the first ovarian cycle was independent of protein feeding, but a protein feed was necessary to complete the cycle, and a further protein feed was needed to complete the second ovarian cycle. No development in the first cycle took place below 57°F, but between 58 and 78°F development was progressively faster. Unfertilised females developed and laid the first batch of eggs, but were unable to complete a second batch. Oviposition was delayed by lack of favourable sites, and after one week fertility was progressively reduced. It is shown that, because of these variables, valid estimates can be made only of the minimum age of female bushflies.

The literature on age-grading techniques of adult insects, published since 1968, is reviewed. The techniques described include those which deal with changes in the reproductive system, as well as somatic changes which take place with age. They also include techniques based on changes induced by wear and tear. Follicular relics found in different orders of insects are described, and their origin, fate and relative usefulness in age-grading studies are discussed. Attention is drawn to the formation of anomalous, or aberrant dilatations, particularly ones formed as a result of follicle resorption. The suitability of the various techniques to the study of different insect species is compared, and the advantages of using more than one type of age-grading method in the study of one species are discussed. Enough detail of each technique is given to permit field workers to choose and apply the technique most suitable for the study of the insect of their choice, and for the degree of accuracy required by them. Lists of species which have been studied by particular age-grading techniques, or combinations of them, are given. Finally, examples are cited of the types of problems entomologists have sought to solve, often successfully, using age-grading methods.

Observations on the biology of the egg, larval, pupal and adult stages of the bushfly are presented. Many major physiological and behavioural responses and the survival of individuals seem to depend on the temperature and moisture conditions of the environment, and on the quality of animal dung available as food for the larvae. The seasonal distribution of bushfly in Australia seems to be determined directly by this dependence. Temporarily unfavourable areas are apparently repopulated by long distance displacement of adults. No diapausing or other stage resistant to adverse conditions, is known.

In laboratory experiments in Australia under standard conditions, densities of the dung beetle Euoniticellus intermedius (Reiche) exceeding 150/1-litre pad of cattle dung were shown to suppress breeding of Musca vetustissima Wlk. The experiments also suggested that it was the effect of dung disturbance on the survival of eggs of the fly that led to suppression. Natural vaiation in the quality of cattle dung obscured but did not alter the effects of high beetle densities. The mobility of M. vetustissima in particular, obscured the relationship of its abundance to dung beetle numbers in the field in 1974–75 and 1975–77 an intial high level of flies was apparently reduced and suppressed by a seasonally late but otherwise similar level of beetle attack on dung pads.

The distribution and seasonal activity of Onthophagus granulatus Boh. was studied at two sites in eastern Australia. It is a univoltine species, with peaks of activity in spring and early summer. Breeding cycles and periods of stress were demonstrated by the proportions of newly emerged, nulliparous and parous beetles and those resorbing oocytes. The optimum temperature for brood production was 25°C. The threshold of development was 11·3°C, and 495 day-degrees C were required for development from egg to adult. Dung quality and drought were important factors affecting survival and brood production in the field. The distribution of the species in south-eastern Australia is limited by summer rainfall and temperature.