The life habits of codling moth in the Australian Capital Territory are described, and the ecological characteristics of the species and its environment are defined. In the Capital Territory, codling moth produces a complete first generation, a partial second generation, and some third generation individuals each summer. On an average, females lay between 40 and 50 eggs in all generations, but fecundity varies much between individuals. The observed distribution pattern of eggs and larval injuries to fruit suggest that oviposition occurs predominantly on trees at, or near, sources of females. In uniformly infested, homogeneous orchards, egg and damage distribution are almost random between trees. No significant departure from randomness was detected either between fruits, or between locations within trees. Fruits are often penetrated by more than one larva, either simultaneously or in succession, and competition occurs. Its forms and effects were examined. Fruits penetrated by several larvae tended to produce more mature larvae than fruits penetrated once, but the chances of survival fell as the numbers of entries per fruit increased. Fully fed larvae move from the fruit to an appropriate place on, or very close to, the host tree, where they spin a cocoon and eventually pupate. Under natural conditions in the Capital Territory, most mature larvae perish before establishing a cocoon. The rate of establishment was shown to be directly dependent upon the abundance and accessibility of suitable cocooning sites. The injuriousness of codling moth is always extremely high in the Capital Territory because of the generally favourable weather conditions. Particular effects of climate and weather on codling moth activity are discussed. Optimum environmental conditions for codling moth are defined. Conditions in the Capital Territory were found to be nearly optimum in most respects. Codling moth abundance cannot be explained by single ecological factors. Comprehensive studies of local populations are required to understand the numerical determination of the pest.

Light‐brown apple moths (LBAMs) are Australian leafrollers of the genus Epiphyas, capable of infesting orchards and other horticultural crops. Currently, five species are recognized, two of which, E. postvittana and E. pulla, can be serious economic pests. By means of principal‐components and group‐average cluster analyses applied to six parameters of demographic performance, two forms suspected of being interspecific hybrids were tested comparatively with possible parent species, and were found to be indistinguishable from E. postvittana. The frequency distribution of cornuti, a structural feature of the male genitalia used in identification, was investigated experimentally in the two economic species and their hybrids. The numerical variability of this character was shown to be much greater than had been recognized previously. It was found also that, in E. postvittana, cornuti frequencies may change in response to environmental influences. Hybrids tended to have cornuti numbers intermediate between those of their progenitors. LBAMs seem to be undergoing rapid evolutionary change in response to man‐induced alterations in the environment, and represent a hazard to horticulture not only in Australia, but possibly also in any temperate or sub‐tropical region to which they might gain access overseas. The situation would justify undertaking a systematic, Australia‐wide, survey of these and related leafrollers.

A population study of the light-brown apple moth (LBAM), Epiphyas postvittana (Walker), was pursued from 1963-64 to 1966-67 in a naturally-infested, unsprayed apple plantation near Canberra. The investigation covered the period of tree development leading up to and including, the production of the first substantial crop. The life history of LBAM and the occurrence of natural enemies were examined. The species did not produce seasonal series of identifiable generations, but individuals in all development stages tended to co-exist as cohorts of uncertain generation status. Whereas numbers of LBAM decreased gradually from 1963-64 to 1965-66, they rose again markedly in 1966-67, following the release in the study area of about 3,000 laboratory-reared moths. From periodic field surveys and complementary experiments, it wtis inferred that the population dynamics of LBAM in the study area consisted essentially in the production of excessive numbers of immature stages, which were reduced by natural enemies to much smaller cohorts of mature stages, determined by the ability offiuit trees to supply the LBAM's requisite food and shelter. It is argued that this ability, i.e. the carrying capacity for LBA M, decreased as the trees matured, and that the damage of LBAM in the crops of fully-bearing trees would have been negligible under the conditions prevailing in the study area.The probability of damage to fruits was directly proportional to the numbers of larvae and of fruits present, indicating that, unlike codling moth for instance, LBAM did not seek out fruits for attack, but struck them by chance encounter.The results of this life-system analysis are discussed in the light of Southwood & Comins' (1976) and Southwood's (1977a, b) generalizations on population dynamics, ecological strategies, and the stattis of pests. LBAM is believed to display all the characteristic features of an 'intermediate strategist' and an 'intermediate pest'.

No abstract

Whereas populations of Epiphyas postvittana (Walker), the light-brown apple moth (LBAM), normally produced a slight preponderance of male adults in laboratory cultures, males tended consistently to be less abundant than females in samples drawn from Australian field populations. The sex ratio ofthe species was investigated with a view to explaining this fact. A condition, causing bisexually-reproducing females of LBAM to form viable progenies comprising mainly female individuals, was found to affect 7% of females in population samples from the south-eastern mainland of Australia, and 4% from Tasmania. A statistical model describing the distribution of the condition in field populations is given. The origin of the condition is unknown; the causative agent is believed to act by inducing the death of male embryos. The condition was only observed to be transmitted from mothers to daughters, of which some might produce apparently normal progenies, while others produced either allfemale or predominantly-female progenies. The demographic performance of affected females differed from that of comparable 'normal' individuals only in fertility, which was significantly reduced. In a limited number of experiments, laboratory populations formed from field-collected samples containing 0307-692X/78/1200-0467 $02.00 © 1978 BlackweU 30 affected females, which produced a proportion of males, could only be maintained through subsidies of males from non-affected stock. The present case was considered in relation to literature reports of similar conditions affecting a dipteron, a coleopteron, and a macrolepidopteron. In E. postvittana, it is surmised that the condition might contribute to optimizing the sex ratio of populations comprising affected individuals, thus increasing their adaptive fitness. A set of verifiable hypotheses are formulated concerning future trends in the condition's natural distribution and frequency.