The paper describes fruit sampling carried out in eastern Australia during January 1960–March 1962 to assess the status of parasites of the oriental fruit fly (Dacus dorsalis) liberated in Australia during 1956–1959 against the Queensland fruit fly (Strumeta tryoni). Opius oophilus was the only introduced parasite extant on the mainland in 1962, parasitizing up to 78% of the host fly stages in Averrhoa carambola in north Queensland and 0–35% in other fruit types. O. oophilus was well established in north Queensland at five localities near Cairns and two near Innisfail, and less well established at three localities near the Queensland–New South Wales border. It had died out during 1960 from two localities further south in New South Wales in which it had been well established since late 1958. O. oophilus was present on Lord Howe Island from October 1959 to March 1961 but died out subsequently. O. longicaudatus was extant in low numbers on the island in 1962. Under Australian conditions Opius oophilus mated satisfactorily. The parasite was able to utilize as hosts fruit flies of the following species: Strumeta barringtoniae, S. cacuminata, S. humeralis, S. tryoni, and possibly Afrodacus jarvisi and S. kraussi, but preferences could not be measured with available techniques. Although it was reared from a total of 14 types of fruits, O. oophilus displayed marked discrimination between fruits, but the preferences varied with season and locality. The most consistent preference was for Averrhoa carambola in north Queensland. O. oophilus showed no preference for operating in the more highly infested fruits of any of the six fruit types tested. The maximum dispersal recorded of a population of O. oophilus from a liberation site was 5 miles, 46 months after establishment. A review of climatic factors indicated that winter temperatures of 60°F or less were unfavourable to the persistence of O. oophilus. The presence of O. oophilus was not associated with a reduction in the degree of infestation of fruits. It is suggested that this is contributed to in the north, where climatic conditions for the parasites are favourable, ,by the presence of abundant fruits which are infested by Dacinae but not favoured by the parasite.

Ceroplastes sinensis Del Guercio was recorded for the first time in Australia in August 1966, in the vicinity of Sydney. The scale is widely distributed overseas, occurring in Europe, Africa, China and New Zealand. It infests a wide range of host plants including commercial citrus. Males occur but comprise only about 3 per cent. of the population. The male insecthas 6 instars, one of which, the true third instar, is described for the first time. The principal natural enemies of C. sinensis are Aneristus ceroplastae Howard, Metaphycus helvolus (Compere) and Scutellista cyanea Motschulsky. Their current abundance is too low to influence the abundance of the scale.

In 1950, a programme was initiated to utilize against the Queensland fruit fly (Strumeta tryoni) parasites which were introduced during 1948–1950 into Hawaii, where they produced a considerable reduction in the incidence of oriental fruit fly (Dacus dorsalis). The present paper describes the work carried out under this programme up to October 1959. During 1951–1957 the emphasis was on rearing, at Sydney, on Queensland fruit fly, stocks of Opius longicaudatus and O. oophilus from small stocks imported from Hawaii. It was found that O. oophilus, O. vandenboschi, and O. longicaudatus could parasitize Queensland fruit fly in the laboratory, and that O. longicaudatus could parasitize the Solanum fruit fly, Strumeta cacuminata, which occurs widely in the distribution area of the Queensland fruit fly and hence might act as a valuable alternative host for the parasites. Liberations were made at Coffs Harbour and Sydney in New South Wales in 1956–1957 of 21 000 O. longicaudatus and 1 700 O. oophilus, but establishment was apparently not achieved. The programme was changed in 1957 to provide for larger releases over n much wider area. In view of production difficulties at Sydney, a field station was set up in Hawaii to rear parasites, which were shipped to Australia by air, checked in quarantine at Sydney, and despatched to various parts of Australia for liberation. Between March 1958 and October 1959 the following numbers of foreign parasites were liberated: O. oophilus, 229 200; O. vandenboschi, 28 100; O. longicaudatus and closely related species, 198 700; O. incisi, 27 100; Dirhinus giffardii, 2 500; Tetrastichus giffardianus, 2 500; and Syntomosphyrum indicum, 3 200. The liberations in 1958–1959 were made at 25 locations in New South Wales, 59 in Queensland, 12 in Western Australia, and 6 on Lord Howe Island. The liberations were made in the presence of populations of Queensland fruit fly in New South Wales, Queensland, and on Lord Howe Island, and of Mediterranean fruit fly (Ceratitis capitata) in Western Australia. Data from a total of 185 fruit samples taken between January and August 1959 in New South Wales and Queensland indicate that O. oophilus was possibly established in five localities in New South Wales and two in Queensland, and that some field breeding had occurred of O. vandenboschi and O. longicaudatus in New South Wales. There were no recoveries indicating field breeding of the three species in central or north Queensland. The indications of establishment of O. oophilus are tentative because the relevant samples were taken before the parasite populations had been subjected to winter conditions. There were no recoveries of O. incisi, S. indicum, or T. giffardianus.

Infestations of Boophilus microplus (Canestrini) were established by applying single batches of larvae to individually stalled cattle, and the percentage yields of engorged female ticks from animals kept in harness to impede licking were compared with those from animals allowed to lick freely. In the harness trials, 33 per cent. of female ticks survived to fall as engorged adults from the host; in individual infestations this survival ranged from 5 to 69 per cent. In the trials without harness the corresponding survival was 9 per cent., ranging from 0.1 to 32 per cent. Statistical analysis showed a highly significant effect of harness in promoting survival of ticks. Licking (and other forms of host behaviour, e.g. kicking and rubbing, which produce tick mortality by mechanical means) must be considered in any study of natural mechanisms regulating cattle tick populations.

Studies were undertaken during 1948-1950 on Boophilus microplus under field conditions in southern Queensland to determine the duration of the non-parasitic stages, and to relate this information to tick incidence on cattle. In the area where the observations were made, the population of ticks on cattle is high in summer and autumn and low in minter and spring. Each week throughout the investigation engorged female ticks, freshly fallen from cattle, were placed in a pasture plot and their subsequent history recorded. Concurrently, observations were made on the changes in tick population on a dairy herd on an adjacent farm. Female ticks exposed on the plot between April and July produced virtually no progeny, and it is probable that the ticks in the pasture traversed by the dairy cattle exhibited a similar, though less severe, inhibition of reproduction. This failure to reproduce, combined with the dying out of larvae and protracted developmental periods of eggs, reduced to very low levels the larval population available to infest cattle during the months of August–October. Ticks exposed from late July to the following autumn produced progeny. There was a tendency for the progeny of ticks exposed in the late winter and early spring to hatch a t about the same time in the late spring, and this synchronous hatching was probably responsible for the 'spring rise' in tick population on cattle. It appears likely that the engorged female adults dropped in the early autumn represent the most important stage in the overwintering of the species in this area. Some of their larvae survive the adverse winter conditions, either in the free-living or the parasitic stage, and give rise to adults, which fall in the late winter and spring, and which in turn produce the larvae of the spring rise.