Four designs of trap, all made from identical material, were compared at Galana Ranch, south-eastern Kenya, as sampling devices for Glossina pallidipes Austen and G. longipennis Corti. The NG2G and Epsilon traps caught more than twice as many female G. pallidipes as the biconical trap, and the F3 was intermediate. A similar, pattern was observed for males, although the differences were smaller, and not significant. The NG2G, Epsilon and F3 traps all caught approximately twice as many male and female G. longipennis as the biconical trap. Acetone (500 mg/h) significantly increased trap catches of G. pallidipes, and there was a synergism between acetone and 4-methylphenol (0.8 mg/h). There was little or no effect with 1-octen-3-ol (0.8 mg/h). Acetone, 1-octen-3-ol, and 4-methylphenol all increased trap catches of G. longipennis, and there were no synergisms among them. Cow urine (850 mg/h) increased the catches of both species in traps baited with acetone and 1-octen-3-ol, although not significantly for G. longipennis. There was no effect with 3-methylphenol (0.8 mg/h). The addition of 3-propylphenol to traps baited with acetone, 1-octen-3-ol and 4-methylphenol had no effect on the catches of either species. For G.pallidipes, a combination of acetone, 1-octen-3-ol, 4-methylphenol and 3-propylphenol was calculated to have a catch index of 6–8 over unbaited traps, a value lower than that reported for Zimbabwe and Nguruman, Kenya, and greater than that reported for Somalia. The catches of G. longipennis were approximately three times higher on electrified targets than in F3 traps, although there was no difference in the catch of G. pallidipes.

A plot of cocoa trees at the Cocoa Research Institute, Tafo, Ghana, was inspected weekly for the presence on each tree of 18 species of insects. The 306 consecutive weekly records of percentage of trees occupied by each species were subjected to time series analysis. Auto-correlation and partial auto-correlation functions were calculated for each series and used to identify simple autoregressive linear models to account for the serial correlation. It was found that all species needed a stabilizing autoregressive parameter of lag 1 and all but four a second autoregressive parameter of lag 2. Seasonal autoregressive parameters at lags 3, 4, 5, 7, 9, or 13 were needed for over half the species, either in addition to the parameter at lag 2 or in place of it. It is postulated that these seasonal parameters mimic generation cycles. Runs of the models using random inputs produced series which were close to the originals in general form. The models could be further refined by adjusting the fixed mean levels assumed by the models to take into account the effects due to the abundance of young extension growth on the trees and atmospheric moisture, as measured by afternoon relative humidity readings. Although the production of extension growth is cyclical it would seem that it does not induce the cyclical behaviour observed in some of the insect series. The peaks in the latter cycles are, however, reinforced when they coincide with peaks in extension growth.

The Simulium sanctipauli Vajime & Dunbar subcomplex of the West African S. damnosum Theobald complex is cytotaxonomically revised for the western part of the Onchocerciasis Control Programme area. The subcomplex is defined and a chromosomal key provided for the identification of the sibling species and forms recognized. Two sibling species are newly described, S. leonense Boakye, Post & Mosha (Sierra Leone) and S. konkourense Boakye, Post, Mosha & Quilleévéré (Guinea and Sierra Leone). Detailed chromosomal data are provided as warranty for the conclusions about the specific or infraspecific status of the taxa recognized.

Field sampling of populations of Sitobion avenae (Fabricius) on spring wheat in the north-western USA from 1988 to 1991 produced a data set consisting of 47 estimates of mean aphid density (m; number of aphids per tiller), variance (s2) and the proportion of tillers (PT) with no more than T = 0, 1, 2, …10, 15, 20, and 25 aphids, respectively; defined as the tally threshold. The average sampling error level of the four-year data set was 0.196 (SE= 0.013). The empirical relationship between m and PT was developed for each T value using the parameters from the linear regression of ln(m) on ln[-ln(Pϒ)] and was satisfactory when T = 2, 3, 4, and 5 (as evidenced by the high r2 values and relatively small mean squared errors from the regression analyses relating to the T values). In comparing the variances estimated from different formulae for predicting m from PT, the variance of Binns & Bostanian (1990b) was found to be more conservative and reliable in estimating the prediction variance. This variance was used in the development of binomial sampling plans for each T and in the determination of associated sampling precision denoted by the half-width of the confidence interval (d). Binomial sample sizes based on the T values of 2–5 were found to be associated with relatively small d values that may actually be reached and thus, are recommended for use in monitoring aphid populations for control decision making. However, at population densities below one aphid per tiller, binomial sampling was found to be feasible only when counts were based on empty tillers (T = 0).

The probablity that tsetse flies (Glossina spp.) cross a barrier of odour-baited targets is calculated for barriers of different widths and target density, and for tsetse flies with varying natural rates of survival, daily step lengths (d) and probabilities of being killed by an odour-baited target. If the barrier is only as wide as d, and for a species which has a 2% natural daily mortality and a further 2% mortality due to each target per unit area, tsetse flies have probability (P) of ca. 0.1 of penetrating the barrier even if the target density is 64 per unit area. To ensure that P < 0.001 the barrier must be about 4d wide for target densities 32 per unit area; doubling the width to 8d means that target densities could be cut by about 75%, and total numbers of targets in the barrier by 50%. These biological considerations and the economic costs of different target barriers suggest that, for all tsetse fly species, a safe and relatively inexpensive barrier is achieved with barrier width 8d when the optimum target density is roughly the same as for normal operational areas. This has the important practical consequence that there is no need to treat barriers as a special case. Practical results from research and control operations in Zimbabwe are in accord with the theoretical findings, but further work is required to ascertain whether the safety margin, and hence costs, can be reduced.

The genus Padaukia is newly described in the family Psyllidae. Its systematic relationships are discussed; seven species are included, five of which are newly described: P. cuanzae sp. n., P. javana sp. n., P. kino sp. n., P. macrocarpae sp. n. and P. usambarensis sp. n. An identification key is provided. Three species are known to attack economically important species of timber trees of the legumious genus Pterocarpus in tropical Asia.

The different stages of Hindola striata Maa in Java and H. fulva Baker on clove (Syzygium) in Sumatra were investigated. Data are presented on the duration of egg and nymphal stages and their positions on the plant. Hymenopterous and Dipterous parasites attacking the eggs and nymphs are described. The natural enemy complex of these clove-dwelling insects is contrasted with that of H. viridicans Stål on Melastoma sp. Some observations on adult behaviour and biology are made, particularly as these relate to the spread of Sumatra disease.

Morphological studies of different populations of what was previously considered to be a single species, Telenomus busseolae Gahan, revealed a complex of three distinct species. A total of four species were found to belong to this complex, all of which are egg parasitoids of stem boring Lepidoptera belonging to the closely related noctuid genera Busseola and Sesamia, with a single record from the pyralid stem borer genus Coniesta. All these host genera are of major economic importance as cereal pests. Two of the four Telenomus spp. are fully sympatric with regard to distribution, hosts and oviposition period. Two species, Telenomus isis and Telenomus nagarajae, are described as new.

Male pupae of the tobacco hornworm, Manduca sexta (Linnaeus), were exposed to γ–radiation from a 60Co source. This treatment induced mortality and malformations in the emerging adult insects. The incidence of these adverse effects of radiation declined with increasing pupal age at the time of treatment. Within any one age class, the effects of radiation treatment increased with increasing dose. When 16 d old pupae were irradiated, the resulting adult male insects exhibited adverse effects on mating behaviour and fertility when tested against unirradiated females. These effects were dose dependent in the range 0–30 krad. The major cause of reduced fertility was the failure of eggs to hatch. These eggs mostly showed no sign of embryonic development. F1 progency of moths given substerilizing doses of radiation showed significantly elevated larval mortality, pupal and adult malformations, and a slightly prolonged developmental period, but nevertheless a high proportion of the F1 insects survived to adults. The sex ratio of the F1 generation was markedly skewed in favour of males. When F1 insects, male or female, were mated with normal insects of the opposite sex, they were significantly less fertile than the irradiated parental (P1) generation. The F1 male moths transferred spermatophores to normal females only slightly less well than normal males, but the F1 females were much less successful than controls in mating with normal males. Examination of spermathecae of normal females mated with F1 males showed that both eupyrene and apyrene spermatozoa were successfully transferred from the spermatophore in all cases where the P1 insects had received 10 krad, but there was a slight reduction in the cases of higher doses. There was a dose-related decline in the number of eggs laid per mated female, and a dose-related reduction in hatching rate for the matings of both male and female F1 insects, but the effect on males was more severe than on females. The longevity of both F1 males and F1 females was reduced. The reduction in fertility of the F1 insects was in part due to a reduction in the number of eggs laid, but also to an increase in the number of eggs which failed to hatch. In contrast to the P1 generation, the reduction in hatching success of eggs laid by F1 insects was due mostly to the death of partly developed embryos.

The developmental rates and fecundity of two important African maize pests, Sesamia calamistis Hampson and Eldana saccharina Walker, were studied under constant temperatures and with two larval diets. Five temperatures (15°, 20°, 25°, 30° and 35°C) were used to investigate developmental rates and three temperatures (20°, 25° and 30°C) were used in fecundity experiments. Larvae were reared on maize stem cuttings and on artificial diet. The developmental period for S. calamistis on artificial diet required over 700 degree-days (DD); eggs needed 122 DD above a threshold of 9.7°, larvae required 383 DD above 12.2°C and pupae 204 DD above 10.2°C. The developmental period for E. saccharina on artificial diet was 665 DD; eggs required 125 DD above 9.1°C, larvae 400 DD above 10.6°C and pupae 140 DD above 8.8°C. On artificial diet both species developed faster and had higher threshold temperatures for larval development than when reared on maize stem cuttings. Pupal development rates did not differ between artificial diet and maize stem for either species, although developmental thresholds were marginally lower on artificial diet. S. calamistis averaged 250–690 eggs/female although some individuals produced more than 1000 eggs. Adult females lived 5.7 days at 30°C and 10 days at 20°C. E. saccharina females produce more eggs and lived longer than S. calamistis females. Average fecundity for E. saccharina was 470–620 eggs/female, but several individuals produced more than 1200 eggs. Adult females lived 6.6 days at 30°C and 14.6 days at 20°C.

The frequency of defecation in relation to constant0/simulated outdoor temperatures and larval age (instar) was examined under laboratory conditions in four species of pine sawflies (Diprionidae): Gilpinia frutetorum (Fabricius), Diprion pini (Linnaeus), D. similis (Hartig) and Macrodiprion nemoralis (Enslin). Defecation interval and total faecal production was regular under higher constant temperatures (higher production in younger instars, second and third) and production significantly decreased under varying air temperatures during the same period (24 hours) when larvae of younger instars were influenced more by lower temperatures. The influence of larval age (instar) on faecal production was insignificant if larvae were exposed to varying temperatures during 24 hours. Faecal production and temperature were positively correlated in each of the four species and instars tested, as well as in total (all the test species and instars combined). Implications of the results for estimating canopy larval density by frass-drop measurements in the field are briefly discussed.

Megalurothrips sjostedti (Trybom) is an important pest of cowpea (Vigna unguiculata) in West Africa. Three key factors assumed to be responsible for its pest status are analysed, the survival on alternative host-plants during the dry season, the inefficient biotic mortality factors regulating population growth, and the effect of larval feeding on the development of cowpea flower buds. Extensive surveys indicate clearly that M. sjostedti survives the dry season on a wide range of alternative hosts all belonging to the Leguminosae, where it can feed and reproduce. Different antagonists were observed attacking eggs and larvae of M. sjostedti; their impact, however, is low and cannot prevent pest outbreaks. Two undescribed Megaphragma spp., and one Oligosita sp., all trichogrammatid egg parasitoids, were recorded for the first time. The anthocorid Orius sp. was the most important larval predator. No hymenopterous parasitoids could be reared from larvae collected on cowpea and three major alternative hosts, whereas a low percentage of the larvae collected from the flowers of Tephrosia candida, an exotic shrub native to India, were parasitized by the eulophid Ceranisus menes (Walker), also recorded for the first time in Africa. The feeding activity of six larvae of Megalurothrips sjostedti during five days induced the shedding of all flower buds of a cowpea inflorescence. The results of the analysis shed new light on the M. sjostedti pest problem, and the ways to solve it. The lack of efficient antagonists, particularly larval parasitoids known from closely related south-east Asian Megalurothrips spp., and the high damage threshold, indicate that M. sjostedti is a potential target for biological control. However, further studies are needed to investigate the migration of M. sjostedti adults to and from alternative host-plants, in order to reinforce the action of biocontrol with cultural pratices.

Food-baited dishes were used to monitor the impact of ground-sprayed DDT (4% WP @ approx. 200 g/ha) and deltamethrin (0.05% SC @ 2.6 g/ha) for tsetse fly (Glossina spp.) control, on epigeal ants in mopane woodland in north-western Zimbabwe. Twenty species of ants were recorded at dishes baited with various types of food. Pheidole spp. and Monomorium opacum Forel (Formicidae: Myrmicinae) were predominant, both in the number of baits attended and in the number of workers present at individual baits. Season apparently had a greater effect on the composition and activity of the ground foraging ant assemblage than did either pesticide. There was a decline in the rate at which baits were found and in species richness of the ant assemblage as the dry season progressed and several species also showed changes in their ability to locate baits. There was no major pesticide induced disruption of the species richness or food finding ability of the diurnal ground foraging ant assemblage sampled. However, foraging success by Platythyrea cribrinodis (Gerstaecker) (Formicidae: Ponerinae) was reduced immediately after spraying with deltamethrin. Subtle effects of either insecticide on rarer species cannot be discounted from the results of this study.

An account is given of the development of aqueous gum-chloral mounting media used for mounting small arthropods on microscope slides. Berlese’s fluid is shown to have never been used by Berlese and other formulae are shown to have been randomly attributed to various authors, often incorrectly. Erroneous formulae and modifications to formulae have been followed by subsequent workers without reference to their origin. Details of the five formulae currently recommended in the literature are given and serious problems are shown to have been encountered with all of them by many workers. In many collections throughout the world gum-chloral slides are steadily deteriorating and specimens becoming irretrievably lost. Those workers advocating the use of gum-chloral aqueous media continue to propose alternative techniques in an attempt to overcome the problems they admit still occur. It is recommended that these media be used only for temporary mounts and never for specimens of taxonomic significance.

Field studies in Zimbabwe showed how targets 1 m tall and 25–400 cm wide, composed of vertical panels of visual material and net and baited with odours of acetone, 1-octen-3-ol, and phenols, could be refined for controlling Glossina morsitans morsitans Westwood and G. pallidipes Austen. Attraction from a distance was not affected by swivelling movement but improved several-fold as the width of visual panels increased from 25 to 200 cm. Blue or blue/black targets were about as effective as black for G. m. morsitans but slightly more effective for G. pallidipes. Fine and coarse net was unattractive at long range but the flies avoided coarse net when close. The percentage of tsetse alighting on visual panels before flying round increased up to several times when the panels were widened, and when non-shiny black replaced blue or shiny black, but the percentage of flies alighting before departure was not much affected expect by panel width, being near 0% at 25 cm and 85% at 2 m. Most tsetse alighted first near the centre of targets, especially where black contrasted with nearby blue. Studies of various fabrics and paints and of restricted deposition of insecticide suggested several disposable targets that could have the costs of materials and insecticide, with efficacy preserved for G. m. morsitans and increased by up to 50% for G. pallidipes.

The two spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a pest of cotton in Australia yet has received little attention. To develop sampling strategies for pest management the seasonal abundance and intra-crop distribution of T. urticae on cotton was studied. T. urticae colonized cotton crops at seedling emergence in October. Populations declined through November/December then increased progressively thereafter, at varying times and rates. Higher initial infestation levels were correlated with earlier, potentially more damaging, mite outbreaks. Survival of T. urticae through November/December appears crucial in determining the extent to which this potential is realized. Nodes 3 to 5 below the terminal were most heavily infested and should be used as the sampling unit for mites. The within plant distribution of T. urticae was unaffected by cotton variety or insecticide applications. T. urticae was more abundant on the edges of fields than in the interior early in the season (October and November) indicating colonization from an external source. The edge effect diminished with time, suggesting a lack of continuous colonization. The only exceptions to this pattern occurred when T. urticae migrated from senescent maize crops into the nearby cotton crops in early January. A simple sampling technique, based on the presence or absence of mites on leaves was developed for pest management purposes.