The egg production of females of Ixodes ricinus (L.) was found to be closely related to the engorged body weight. The relationship was due almost entirely to the size of the blood-meal. Smaller ticks seemed to be slightly more efficient than larger ones in converting their blood-meal to eggs. Ticks, especially larvae, that overwintered in diapause did not survive as well as those that fed and then moulted in the same year. Larvae that fed and entered diapause early in the autumn did not survive as well as those that fed later in the season. A very high proportion of tick eggs hatched, either in the same year as they were laid or after overwintering. Almost all nymphs and adults became active and climbed to the top of the tubes after moulting. Although most larvae appeared to become active, only about half of them reached the tops of the tubes. This is thought to be a reflection on the fact that larvae are adapted to parasitise small rodents. It is suggested that winter temperatures may play an important part in determining the mortality rate of larvae that overwinter in the engorged state.

The taxonomic status of the western Palaearctic crop plant pests Trioza nigricornis Först., T. tremblayi Wagn. and T. brassicae Vasil'ev is discussed, and a related species T. trigonica sp. n. (of which the probable host-plant is carrot) is described. Each species is fully illustrated, and a key to them is provided.

Resistance to chlorpyrifos and other commonly used organophosphate larvicides was found in Culex quinquefasciatus Say from several urban areas in Tanzania. Lower levels of resistance were found in laboratory strains of the complex of C. pipiens L. collected in Sri Lanka, Egypt, Liberia and Brazil. Crosses of the Tanzanian strains to a more susceptible strain gave results consistent with causation of the resistance by a single gene or closely linked group of genes. Electrophoresis of one of the Tanzanian stocks indicated two esterase bands of high activity. The resistance in Tanzania did not prevent larval killing by freshly sprayed chlorpyrifos, but it is suggested that a spraying would probably no longer remain effective for three months as reported in earlier field studies.

A pyralid moth belonging to the Marasmia generic complex of leaf-rolling defoliators of rice in S.E. Asia is described and named M. patnalis sp. n. It is differentiated from M. bilinealis (Hmps.), M. ruralis (Wlk.), M. suspicalis (Wlk.) and Cnaphalocrocis medinalis (Gn.), with which it had previously been confused because of similarity of the adults and shared host-plant association.

p. 329, column 1, line 5, for ‘ Cx.’ read ‘ Cs.’

p. 436, line 22, for ‘ no.’ read ‘ n.’

p. 669, line 9, delete ‘and egg survival remains high (7≥ 79%) for a wide range of saturation ’ and insert'. The response function, shown in Table III, was highly significant (P≤00001)’

p. 706, transfer figure but not caption to p. 712 as Fig. 10

p. 712, transfer figure but not caption to p. 706 as Fig. 5

Catches of Musca vetustissima Wlk. in West Australian blowfly traps containing week-old baits were consistently greater (4·5–24·1 times higher) than in traps with fresh baits. Recovery of marked flies within 26·5h of release showed mean dispersal distances of 1·5 ± 0·7 km for males and 1·6 ± 0·6 km for females under favourable weather conditions (mean air temperature 28·8°C and mean wind speed 5·5 m/s). The recovery rate of males (1·3%) and females (1·0%) over this period indicates the feasibility of using single mark-release experiments to estimate absolute fly densities. It is shown that estimates having a 95% probability of being within ± 10% of the true population density could be achieved by the release of 39 000 marked flies.

Laboratory and field experiments were carried out in Australia to determine the effect of arthropods in cattle dung on the survival of the eggs and larvae of Musca vetustissima Wlk. They were tested in the numbers in which they came to dung pads near Canberra, during the 1978–79 and 1979–80 seasons. Laboratory tests indicated that the mite Macrocheles glaber (Müll.), the hydrophilid Cercyon sp. and the histerid Saprinus sp. were all very effective predators. The native dung beetles Onthophagus granulatus Boh. and O. australis Guér. exerted only a marginal controlling effect; and the staphylinid and aphodiine beetles were found to be largely ineffective. The control exerted by the total field fauna when brought into the laboratory was considerable when one or more of the three species of effective predators was present. In the field trials, the control of M. vetustissima was further enhanced by the adverse influence of weather.

A computer model of a tsetse population was developed to determine whether insecticide resistance could evolve as a result of current tsetse control programmes. Chemical analyses were also carried out which showed that Glossina morsitans morsitans Westw. can metabolise DDT to DDE, indicating a potential for insecticide resistance in this species. The model showed that a completely isolated tsetse population stands little chance of surviving attacks with insecticides repeated at short intervals. However, when sufficient time is allowed between applications, such a population may survive and evolution of resistance take place. Given a small amount of immigration, the evolution of resistance is retarded, but population extinction is prevented. The degree of resistance developed by a population also depends on the dominance relationship of a resistant gene with its wild-type allele and on the reproductive fitness of the mutant. It is suggested that control strategies are adopted which would minimise the risk of insecticide resistance becoming a problem in tsetse and that susceptibility studies are carried out both before spraying operations and on any residual population post-spraying.

In a survey of adult ticks infesting livestock in Ethiopia, 33 species and subspecies were identified. The distribution and abundance of each are discussed in relation to ecology (altitude, climate and vegetation). Amblyomma variegatum (F.) is the most widespread and abundant tick parasitising cattle. A. cohaerens Dön. is common on cattle in wetter western habitats but is replaced by A. gemma Dön. in drier eastern areas. A. lepidum Dön. occupies intermediate habitats. The distribution of Boophilus decoloratus (Koch) is similar to that of A. variegatum. Hyalomma truncatum Koch and H. marginatum rufipes Koch are both common except in extremely arid and humid zones. H. anatolicum anatolicum Koch, H. anatolicum excavatum Koch, H. dromedarii Koch, H. erythraeum Tonelli-Rondelli, and H. impeltatum Schulze & Schlottke are usually associated with camels in semi-arid areas of eastern Ethiopia. Rhipicephalus evertsi evertsi Neum., R. sanguineus (Latr.) group and R. simus Koch do not display marked ecological preferences. East of the Rift Valley in semi-arid areas below 2000 m, R. pulchellus (Gerst.) is abundant on cattle and camels. R. longicoxatus Neum. and R. pravus Dön. inhabit drier localities, but R. lunulatus Neum. occurs only in wetter western areas. Species taken infrequently were A. nuttalli Dön., A. sparsum Neum., B. annulatus (Say), Haemaphysalis aciculifer Warb., H. leachii (Aud.), H. parmata Neum., H. spinulosa Neum., Hyalomma marginatum marginatum Koch, H. marginatum turanicum Pom., H. punt Hoogst., Kaiser & Pedersen, Ornithodoros savignyi (Aud.), R. longus Neum., R. muhsamae Morel & Vassiliades, and R. senegalensis Koch. The seasonal dynamics of the common species and observations on their relationships to tick-borne diseases of man and domestic animals are discussed.

Glossina pallidipes Aust. was captured from a moving vehicle and in Moloo traps at three-week intervals from October 1975 to December 1976 in the Kibwezi Forest, Kenya. The percentage of teneral flies captured was about twice as high in the vehicle samples as in the traps. Samples in the traps were mainly of older flies, especially parous females. The numbers of G. pallidipes collected in the traps during 20 two-day periods were correlated with those collected from the vehicle. The vehicle-catch levels were less variable than those in the traps. By both methods the highest numbers were collected in September (cold season) and the lowest in November-December (short rains). Attraction to the vehicle followed a bimodal diel pattern at all seasons, with a higher morning (09.30–10.00 h) than afternoon (17.30–18.00 h) peak, and a midday depression at 13.30–14.00 h; the afternoon peak was much reduced in parous females. At all seasons, only one distinct peak (at 15.00–17.00 h) and very low catches at night were exhibited by flies attracted to the traps.