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.

The method and evaluation of a field application of rubidium chloride for the purpose of a mark-and-recapture experiment are described. In the Philippines, populations of the rice pests Nilaparvata lugens (Stål) and Sogatella furcifera (Horv.) were successfully marked by a foliar spray of rubidium chloride plus surfactant applied to a rice field at 1·03 g/hill. Individual insects marked with rubidium, which were easily distinguishable from unmarked individuals for at least seven weeks, were generated at this dose level, and even after one year elevated rubidium levels could be detected in pooled samples. Other phytophagous and entomophagous insects also became marked.

Recent studies on the ecology of two cereal aphid species, Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.), are reviewed. The most important factors affecting their abundance were used to construct decision trees to assess the risk of outbreaks of these species in the summer in England. These factors for S. avenae were crop sowing date, the size of the autumn migration, the severity of the winter, the size of the spring migration and the incidence of natural enemies in spring and early summer. For M. dirhodum, only the last two factors were considered as it does not occur on cereals until the spring in England. These decision trees were successfully tested using field data from 1983, when no outbreaks of either species occurred due to the effects of natural enemies.

The aphelinid Encarsia bennetti sp. n. is described from material collected in India and associated with Aleurocanthus woglumi Ashby, a pest of citrus.

Based on data collected during regular, biconical trap sampling of Glossina palpalis palpalis (R.-D.) over two and a half years during and after two insecticide programmes in Ivory Coast, various analytical techniques were developed which allow the estimation of mortality rates and life-time fertility from ovarian age distributions of female flies. Data from trapping-out experiments were used to calculate the natural resilience of local populations. The results reveal that the dynamics of the populations showed considerable local variation, with two major types of sites. At those sites with large numbers of domestic pigs, the fly population was dense and showed a high degree of natural resilience and a low mean mortality rate, so that it could be selfsustaining through reproduction alone. At sites with few pigs, the fly population was scarce and showed a lower degree of natural resilience and a higher mean mortality rate such that the population could only be maintained by continuous input of immigrant flies. Studies of the natural dynamics of tsetse can be used to predict the likely effectiveness of alternative control schemes; fly mortality rates must be permanently increased in order to reduce fly numbers or infection rates to below some threshold for disease transmission.

An analysis of the population changes of Glossina palpalis palpalis (R.-D.) during and after two insecticide trials in Ivory Coast revealed that the effects of insecticide application depend very strongly on the characteristics of the population ecology of the fly, which showed considerable local variation. At sites with high fly populations and low natural mortality rates, the populations declined rapidly during the spray period as the insecticide killed a large proportion of the local, mainly resident, population. The high resilience of the populations, however, permitted rapid recovery, largely through reinvasion from neighbouring areas, so the reduction in fly numbers lasted for only 3–4 months at a time of year when, in the absence of insecticide, the population showed a significant seasonal decline lasting for up to three months. At other sites, with low populations and high natural mortality rates, the local populations were supported chiefly by immigrants and therefore insecticides only affected a very small proportion of the total population and thus did not cause an immediate decline in fly numbers. The low resilience of these populations, however, means that any repeated low additional mortality (such as that caused by removal trapping or deterioration of environmental conditions) would cause the populations to decline. Thus at both types of site, but for rather different reasons, single or short-term insecticide applications had a limited effect on the populations, and longterm, repeated control procedures are considered to be the only ones likely to reduce the populations significantly; through economic necessity these must rely on low-technology devices such as insecticide-impregnated screens or traps.

A population of the coconut pest Segestidea uniformis (Willemse) was monitored on a small island 2° from the equator in Papua New Guinea between 1973 and 1978. Totals of 54 000 first-instar nymphs were caught on sticky traps on palm trunks and 8750 other nymphs and adults were recovered from the crowns of palms. Generations were completely overlapping, and there was no evidence of seasonality in population fluctuations. The sex ratio was 50:50 in the first six instars, but 90% of seventh instars and 30% of adults were female. Explanations for these variations are given. The population declined from an annual mean of 24 individuals of all ages per palm crown in 1973 to 9 in 1976 and increased again to 29 in 1978. Most post-hatching mortality occurred as first instars climbed from the ground to the crown of palms, probably due to the lizard Gehyra oceanica and rainfall. The number of adults was more sensitive to mortality occurring after the first instars had arrived in the crowns. This mortality appeared to be related to the duration of periods without rainfall, supporting earlier observations that damaging outbreaks of S. uniformis populations do not occur in places which experience a regular dry season. Production of coconuts appeared to be inversely related to the population density of S. uniformis, which did not rise above a level estimated to cause 20% defoliation of the palms during the study. Nut production also seemed to be related to the number of hours of sunshine received in the preceding 12 months. Biological control aimed at nymphs and adults in palm crowns is suggested as an option for controlling S. uniformis which deserves investigation.

Brood care in Copris diversus Waterh. enhanced survival of progeny. Reallocation of dung from brood balls with no live progeny to brood balls containing live progeny was. a typical behaviour pattern in this species and resulted in fewer, larger brood balls. The advantage of this behaviour is that larger brood balls produced larger progeny, which in turn produced a greater number of offspring.

Several methods for the bioassay of changes in cattle dung as insect food were defined and simultaneously assessed using Musca vetustissima Wlk. Size of emerging adults, in particular head width, was a reliable estimator of changes in the dung, but survival was not. Freezing of dung for 24 h had no effect. Flies of similar size emerged from dung placed on moist sand (field capacity moisture) and on an impermeable membrane; on dry sand, size was greatly reduced when the dung was coarse and less nutritious. The optimal method was deemed to be use of fresh dung on sand at field capacity moisture, leaving flies to emerge and die before measuring the head widths in a sample.

Numicia gauhati sp.n., collected from rice in Assam, India, is described and illustrated. It is compared with other known species of Numicia from the Oriental Region. N. maculosa pusana Ghauri is raised to specific status.

Descriptions are given of two new species of pentatomid bug, one known to transmit the disease ‘marchitez’ (caused by Phytomonas staheli) of oil palm in Ecuador and the other associated with hartrot (caused by the same flagellate) in coconut palm in French Guiana. Notes are included on a third species also associated with hartrot in French Guiana. The species are Lincus lethifer sp.n., L. apollo sp.n. and L. croupius Rolston.

The vigour, i.e. survival and wood consumption, of groups of Coptotermes lacteus (Frogg.) and Nasutitermes exitiosus (Hill) was measured when termites were kept at different population densities by changing group size and/or volume of the holding container. A characteristic pattern emerged for subterranean termite species. At low population densities (<0·01 g termites/ml), performance improved with an increase in group size; at higher densities, it tended to decline. The impact of altering group size and container volume on termite vigour was most pronounced at low population densities; at higher population densities, performance tended to be more stable but declined markedly when termites became overcrowded. In most jar-type experiments on termites, especially those conducted in Europe and the USA, small groups of termites are housed in disproportionately large jars, resulting in very low, sub-optimal population densities. Suggestions are made for improvement in experimental design that would lead to an enhancement of the comparability of results from different laboratories.

Records of daily catches of males of Spodoptera littoralis (Boisd.) at pheromone traps in or near the Nile Delta, Egypt, during 1979 and 1980 were used to investigate both the seasonal variation in catch and the possibility that migration, associated with particular weather systems, may significantly affect moth numbers in a particular area. Although more moths were caught in 1979 than in 1980, in both years there was a similar seasonal variation in catch, with low numbers in January and February followed by an increase to a maximum in June or August. There was no systematic seasonal change in the area of highest catch that would suggest seasonal migrations. On some nights, large increases in catch were associated with weather disturbances, notably windshift lines, suggesting that flying moths are sometimes redistributed by wind systems. Catches at two traps far from the main source area suggest that moths may have flown at least 50 km downwind from sources in the Nile Delta. The pattern of nightly catches at most traps indicated that build-up of local populations is the most important factor affecting the population dynamics of the pest but that some, mainly local, redistribution by wind systems takes place.

The susceptibilities of 14 plastics formulations (four polyethylenes, one polypropylene, one polyester, two polyamides, one polyurethane and five poly(vinyl chlorides)) to attack by Coptotermes acinaciformis (Frogg.) and C. formosanus Shir. in the laboratory were broadly related to hardness and surface finish. Overall, C. acinaciformis inflicted more damage than C. formosanus, despite lower survival, but some formulations appeared more susceptible to C. formosanus than to C. acinaciformis.

In attempts at the biological control of Salvinia molesta in Australia, the curculionid Cyrtobagous sp. was released at eight sites and became established at seven of them. At these seven sites, air temperatures ranged from less than 0°C to more than 45°C and the mean concentration of nitrogen in S. molesta ranged from 1·18 to 1·82% of dry weight. Establishment was effected by releasing 200 adults, and the shortest time for extensive damage to be caused to the weed was four months. Cyrtobagous sp. dispersed in undamaged S. molesta at rates of a few metres per month. The pyralid Samea multiplicalis Gn. was released, and became established, at three sites and spread at least 170 km north and south in 20 months. At the sites colonised, air temperatures ranged from less than 0°C to more than 45°C and the mean nitrogen concentration in Salvinia molesta ranged from 1·34 to 3·30% of dry weight. Establishment was effected by releasing 800 larvae, and the shortest time for extensive damage to be caused to S. molesta was three months. Contrasts in the biology and ecology of the two species of insects are discussed briefly as is competition between them for food. In late 1983, Cyrtobagous sp. had achieved control of S. molesta at five sites, while Samea multiplicalis had achieved control at none. It is suggested that S. multiplicalis might perform better in locations which experience maximum temperatures lower than those in the present distribution.

Alatae of Aphis fabae Scop. which reproduced before their first flight (flyers) were compared in the laboratory with those which did not (migrants) in order to test whether this difference in behaviour could be taken as an expression of migratory urge. No difference in live weight or dry weight could be found between the two groups. Flyers, however had a higher wingloading than migrants after the final moult but not after pre-flight reproduction. Flyers also had a lower fat/dry weight ratio than migrants and appeared to have more embryos, including a greater number in an advanced state of development. The significance of these observations is discussed in relation to two hypotheses which could account for the different behaviour of migrants and flyers. The results support the hypothesis that migrants have an innately greater urge to take off than flyers, mediated by their crowding experience during development, and that this is likely to result in migratory as opposed to trivial flight.

Parapyrus manihoti gen. et sp. n., an encyrtid parasite of Phenacoccus manihoti Matile-Ferrero in South America, is described from the adults of both sexes. The parasite is of potential use as a controlling agent of this mealybug in West and Central Africa where it is established as a pest of cassava.

Eurycoccus cuniculorum sp. n. and E. tamariscus sp. n., are described from Pakistan. They were collected on species of Tamarix during a survey of insect pests by the Commonwealth Institute of Biological Control for possible natural enemies of Tamarix spp. that have become undesirable plants in the USA. The mealybugs live under the bark or in tunnels caused by other organisms and both species have unusual characters in the positions of the thoracic spiracles.

Descriptions, illustrations and measurements of the egg, the five nymphal instars and the adult of Amblypelta theobromae Brown, a serious pest of cocoa on the mainland of Papua New Guinea, are presented. A key for the separation of the nymphal instars is provided.