In this paper the present status of insect chemosterilants is reviewed. Chemosterilants may be categorised into eight main chemical groups. Practical control measures involving the use of chemosterilants are discussed, also the persistence of these substances when applied to the insect. The gross effects of chemosterilants on insect reproductive systems and also the effects on egg develpment when female insects are mated to chemosterilised males are described, including dominant lethality, reciprocal translocation, enzyme inhibition and sperm inactivation. The possibilities of recovery of fertility and insect resistance to the sterilising effects of chemosterilants are discussed. Endocrine misfunction and chemosterilant action are related. The only practical chemosterilants as control agents are the aziridines although mutagenic hazards associated with these substances preclude their widespread usage. The sterilising activity of certain insect hormone analogues and related substances encourages the belief that safe insect specific sterilising agents can be found.

The bionomics and ecology of two Adelgids, Adelges knucheli (Schneider-Orelli & Schneider) and A. joshii (Schneider-Orelli & Schneider), first recorded from West Pakistan by Yaseen & Ghani (1966), have been studied by Ghani & Rao (1966). During surveys for the natural enemies of Adelgids in West Pakistan forests, another Adelges sp. on fir and three Pineus spp. on pines were found. They differed from described species in shape, size and arrangement of the wax pores on the sclerotised plates of the head and thorax, characters considered by Underwood (1963) the best for identifying apterous Adelgid adults. They are here described as new, and notes are given on their biologies seen in marked colonies under field conditions. All four species are monomorphic and anholocyclic.

An effective method of tsetse eradication has been demonstrated on a practical scale in country infested with Glossina morsitans morsitans Westw. in the Western Province of Zambia. An area of slightly over 600 miles2 (1 600 km2) was sprayed from aircraft five times, at approximately three-week intervals, with endosulfan in oil solution at an average of 8·2 gal/mile2 (14·4 litre/km2), so that the area dosage of active ingredient was 17 lb/mile2 (3 kg/km2) per application or approximately 2 oz/acre (0·15 kg/ha) for the whole operation. The insecticide was dispensed as an aerosol (most droplets of 20 μm diameter) made by injecting the spray liquid into the extended exhausts of the aeromotors. Post-spray fly-rounds showed that tsetse eradication was apparently achieved except near an unsatisfactory isolation barrier. The total cost was about K300/mile2 (£175 sterling).

Ten fertilised female Glossina austeni Newst. reared from pupae with a weight range of 17–33 mg were maintained singly in small cages, and were offered food six days per week. The mean data for the flies were 151 days life span, 14–5 pupae per female and 25–4 mg pupal weight. One fly showed an abnormal digestive condition, and several failed to larviposit at the end of a cycle. The weight of pupae produced was related to the total amount of blood ingested in each normal cycle. A comparison between fertilised and virgin flies indicated that 50% of the blood ingested by the former was for pupal production. Large flies took larger blood-meals and fed less frequently than small flies.

The author discusses the restriction of the genus Lepidosaphes to nine Holarctic species by Borchsenius and his assignment to other genera of most species previously placed in Lepidosaphes. These changes in generic assignment have affected the names of many species of economic importance. A key is presented to 13 genera allied to Lepidosaphes.

A review is given of estimates, both published and unpublished, of numbers in some types of desert locust (Schistocerca gregaria (Forsk.)) populations, and suggestions are made for further work in this field. For swarming adult populations, estimates of volume and area density and of the relative sizes of settled and flying swarms have been reviewed. For gregarious nymphal (hopper) populations, the area density of late-instar bands and the infestation rate following gregarious breeding have been examined. There is insufficient evidence to give estimates of the average numbers in any of these types of population with confidence, or to be able to estimate the environmental and physiological factors with which variation in density is correlated. It is not possible to make generally valid estimates of the densities of non-gregariously behaving populations. Practically no research has been done on population estimation methods suitable for such populations, although, in practice, estimates are made during field surveys. The principles underlying valid sampling techniques, and valid selection of the sample in various situations, are described.

This paper describes some characteristics of a granulosis virus specific to the larvae of potato moth (Phthorimaea operculella (Zell.)). Host eggs are laid on the soil or on the potato plant; the newly hatched larvae bore into the leaves, generally through the underside, and then develop in feeding tunnels. Mines occur more frequently on the lower leaves, and on the outermost and larger leaflets. The adults are dispersed by wind. Exposure of larvae to externally borne virus deposits is very brief, but sprays of the virus usually produce high rates of infection even when applied only to the upper surfaces of the leaves. It was established that virus particles can enter treated leaves through the stomata. Infected larvae die in two to three weeks, but an overdose causes death by toxicosis within 48 h. In two small-scale field trials the disease spread to control plots preventing comparison of damage to tubers of treated and untreated plants. In each trial, the sprays started an epizootic which affected almost all larvae on the treated plants. With high host populations and many volunteer plants, the epizootic spread at least 1 000 yd in five years. Under good commercial conditions with low host populations, wind and birds were the chief means of virus spread. The distribution and retention of virus particles on the plant were affected by wetting agents and virus concentration.

The developmental biology of Telenomus remus Nixon is described from rearings within the eggs of Spodoptera littoralis (Boisd.). It has two larval instars and its developmental duration at 25°C is about ten days. Superparasitism can be easily induced in the laboratory, but only one adult emerges from each host egg.

Twelve Trichogramma spp. are redescribed. These are: T. australicum Girault, T. dendrolimi Matsumura, T. euproctidis (Girault), T. evanescens Westwood, T. fasciatum(Perkins), T. japonicum Ashmead, T. minutum Riley, T. perkinsi Girault, T. pretiosum Riley, T. retorridum (Girault), T. semblidis (Aurivillius) and T. semifumatum(Perkins). Differences in male genitalia are emphasised, being most stable and reliable, and pigmentation as well as wing and antennal trichiation are described, being characters of supplementary importance for species diagnosis. Host and distribution records are also given. In the male genitalia, the shape of the dorsal expansion of the gonobase differs considerably in some species and the position of the chelate structures with respect to the tips of the gonoforceps also varies; the median ventral projection is large in some species, reduced in some and almost absent in others. A comparative account of the most distinguishing characters of the different species is included and a key to 15 species is provided

In an inland area of the Gambia the density of flying mosquitoes at successive distances from a pair of bait-calves or an equivalent source of carbon dioxide was measured with ramp-traps to determine the maximum range at which orientation towards the bait was initiated. Thirty-six traps were operated at intervals of 7·5 m up to a distance of 60 m from the bait, on 66 nights. Anopheles ziemanni Grünb., Mansonia uniformis (Theo.) and Aedes spp. were responding to the presence of the baitcalves from a distance of 22·5–30 m; with carbon dioxide as bait the same species showed a clear response at 15 m but, with the doubtful exception of M. uniformis, not at 22·5–30 m. M. africana (Theo.) responded to both calf and carbon dioxide baits at 15 m but not at more distant ranges. Culex thalassius Theo. and C. univittatus Theo. showed a response at 7·5 m but not at any greater distance. C. decens group showed no response to either bait even in the nearest traps (7·5 m). The parous rate in Mansonia spp. varied with distance from the bait. Similar variation in the proportion of females infested with mites was not detected.

Counts were made of Microdiptera hatching in emergence traps from samples of organic substrates from cacao plantations in Bahia, Brazil. Rotten cacao pods provided the best substrate with regard to species diversity and total numbers of insects collected, and also for the subgenus Thyridomyia. Leaf-litter was found to be an important breeding place for the subgenus Forcipomyia, especially F. {F.} genualis (Lw.), and for Atrichopogon species. Epiphytic bromeliads may be an important breeding place for the pollinating subgenus Proforcipomyia.

A granulosis virus was tested on a field scale at Manjimup and Pemberton in Western Australia for control of its host, the potato moth Phthorimaea operculella (Zell.). The virus was produced on laboratory-reared larvae, and applied as a suspension of pulverised larvae (6 275 in 111 gal/ha) to second-crop (December-planted) potatoes. There were untreated and insecticide-treated (DDT, dieldrin, methyl-demeton) fields for comparison. The effectiveness of the treatments was assessed on numbers of larval mines and tuber damage. Virus infection rates of 100% were achieved, with a residual effect of 12 weeks. Variation in larval body weight indicated that initial dosages and those due to recycled virus were excessive, but were optimum after two months. Virus applications were as effective in preventing damage as insecticide treatments. Virus spread to untreated crops some miles distant was attributed to movements of personnel, farm materials or birds.

Observations were made in Ceylon from March 1970 to February 1971 on the post-mortem incidence of Oestrus ovis L. in goats. The incidence of O. ovis was 30−2% in Jamnapari goats but 16−2% in a South Indian breed. Peaks in incidence, seen only in Jamnapari goats, and peaks in the numbers of larvae per carcase, followed the monsoons. There was a significant association between O. ovis attack and symptoms of pleuropneumonia.

In laboratory experiments, all stages of the Egyptian cotton-leaf worm (Spodoptera littoralis (Boisd.)) were killed by exposure at 1–2%C for ten days, but the peach-potato aphid (Myzus persicae (Sulz.)) and the red spider mite (Tetranychus urticae (Koch)) were not controlled by this treatment. When exposed to methyl bromide, all the S. littoralis eggs tested were killed by a concentration × time product (CTP) of 44 mg h/litre at 18%C, but control of all stages of M. persicae and T. urticae required a CTP of at least 88 mg h/litre.

A panteles flavipes (Cam.) and A. sesamiae Cam. are important parasites of graminaceous borers in the Oriental and Ethiopian Regions, respectively. Both have been utilised for biological control. A. sesamiae has become the commonest parasite of Sesamia calamistis Hmps. in Mauritius (Anon., 1954), while A. flavipes has become remarkably successful against Diatraea saccharalis (F.) in Barbados (Simmonds, 1969a). In view of the interest engendered in these parasites, particularly the latter, by these successes, a general account is presented here of their biology, based on published data and on the author's observations at the East African Station (Kawanda, Uganda) of the Commonwealth Institute of Biological Control.

From trials with cotton (variety Stoneville 7A) grown on the Ord River Irrigation Area of Western Australia, the results of delaying insecticide protection of crops against Heliothis attack by four and eight weeks were re-examined. With each delay the crop set later when temperatures were cooler, the plants older and larger, and the accumulated insect damage greater. Yet there was no significant difference in the final number of bolls produced in each crop. The growth of cotton and the compensatory mechanisms of the plant indicated by the data were simulated by a simple computer model. A modification of the model to simulate the response of a cotton plant to attack by Heliothis larvae was also developed. Output from the model suggests that, under the conditions of the experiment, there is a theoretical maximum number of bolls produced by this cotton variety. To produce this maximum crop requires complete protection from Heliothis larvae, but the period of protection can be minimised.

Humidity measurements in air spaces in the soil of Glossina morsitans Westw. breeding sites during the hot-dry season in northern Bostwana proved that ground holes were significantly more humid than tree holes, fallen logs or leaves. Site humidity decreased between September and October but did not differ significantly between riverine and mopane woodlands. Pupal mortality data demonstrated an apparent advantage in the dry season shift of breeding to holes. The evidence is only circumstantial that humidity is involved in site selection.

Cotton stainers (Dysdercus spp.) are members of the family Pyrrhocoridae and many are pests of cotton throughout the tropics. Ten species are found in Africa (Pearson, 1958). Three of these have been established in colonies at Arusha, Tanzania. They are D. cardinalis Gerst., D. fasciatus Sign. and D. nigrofasciatus Stål.

Previous reports and field observations at Ibadan and in northern Nigeria have established the occurrence of a dry-season form and a wet-season form of Zonocerus variegatus (L.). The wet-season form in the savanna areas of northern Nigeria is shown to be virtually identical with that from southern Nigeria on the basis of breeding seasons, habitat and morphometrics. Morphometrics show the wet- and dry-season forms to be distinct. It is suggested that the dry-season form in the wet rain forest zone spread into the dry savanna areas giving rise to a wet-season form adapted to the different climatic conditions. The increasing occurrence of the wetseason form in the south probably represents a re-invasion by the northern wetseason form.

The louvre-trap hut was designed to be cheaper and simpler to use than the verandah-trap hut. The eaves are closed, and mosquitoes enter by way of a row of five louvre frames and leave by a window fitted with a window trap. In three trials at Magugu, Tanzania, window traps fitted over one or all louvre frames showed that the efficiency of the louvres in preventing egress was 66–79% for Anopheles gambiae Giles, 51–73% for Mansonia uniformis (Theo.) and 74–78% for Culex pipiens fatigans Wied. Egress through the louvres of A. gambiae is only slightly more, and of M. uniformis much less, than through the eaves of a verandah-trap hut.