The seasonal occurrence and spatial distribution of the crambine stem borer, Chilo partellus (Swinhoe) were investigated in maize, Zea mays, and sorghum, Sorghum bicolor, fields at the Kenya coast. During the vegetative growth stage, small-sized larvae were typically found behind leaf sheaths and in whorls in maize and sorghum. In reproductive and senescent maize, small-sized larvae were also found feeding in ears. Later immature life stages were located predominantly in stems in sorghum, and in the stems and ears in maize. Density and variance estimates of small, medium-, and large-sized larvae and pupae in maize and sorghum were fitted to Taylor's power law which provided significant regressions in all cases. The between-plant distribution was aggregated in all life stages. In maize, the distribution remained aggregated through the larval and pupal life stages, but in sorghum the distribution became progressively less aggregated as insects aged. The relationship of C. partellus density to the proportion of plants infested also suggested aggregation. Optimal sample sizes were determined for both binomial and enumerative sampling plans at two levels of precision, and a discussion is included on the relationship of optimal sample sizes to economic injury levels. Additionally, a presence/absence sequential sampling plan is proposed.

The effects of intraplant variation of nitrogen, phosphorus, potassium and wafer content within maize plants on fitness of the African armyworm, Spodoptera exempta (Walker), were studied in three experiments by using an excised leaf system. Maize plants were phosphorus deficient in one of the experiments. Various leaf categories were distinguished differing in age and position on the plants. Leaf sections on which caterpillars fed were daily refreshed. Changes in the four plant variables measured, due to the excision and subsequent placement of the leaf sections in the excised leaf system for one day, were small and mostly insignificant. Highly significant differences were found between the composition of the various leaf categories in all three experiments. In all experiments, the nitrogen concentrations ranged from 2.4 to 4.5%, phosphorus from 0.1 to 1.3%, and potassium from 1.4 to 4.8% dry weight, while water content varied from 83 to 90% fresh weight. Of all insect fitness parameters observed, only larval growth rate was consistently and significantly affected by leaf category. Fecundity was strongly correlated with pharate adult weight. Only phosphorus was significantly and positively correlated with larval fresh weight, especially in the experiment with phosphorus deficient plants. Multiple regression models revealed that in all experiments a significant proportion of variation in larval fresh weight between leaf categories could be explained by the four plant variables. However, only phosphorus was included in all models. When all leaf categories used in the three experiments were considered simultaneously, the importance of phosphorus for larval growth rate in these experiments was again evident. The variation in nitrogen, potassium and water appeared to be of little or no significance. The consequences of these findings for outbreak development of S. exempta are discussed.

Reactions of the lemon leaf-cutting ant, Atta sexdens rubropilosa Forel, to natural sources of allelochemicals has been investigated at the University of Southampton. A linear hypothesis model in a randomized block design of a factorial experiment was utilized to assess the responses of the ants to the treatment combinations. When workers were offered flowers and leaves of the specified plant species simultaneously with mesocarp and endocarp of orange, they exhibited a consistent preference for the flowers. Flower fragments comprised 93.64% of the experimental material brought to the nest, leaves 6.20%, orange mesocarp 0.04% and orange endocarp 0.12%. Deterrent effects were noticed in leaves of Scilla spp. (Liliaceae) and the ants were chemically stimulated to explore, cut and transport the highly attractive flowers of Mahonia aquifolium (Berberidaceae).

Over the temperature range 5° to 25°C, fecundity of Panolis flammea (Denis & Schiffermüller) showed a non-linear response, the optimal temperature for fecundity being 15°C. At 6°C females laid 17 eggs each whilst at 15°C they laid 166 eggs. Pre-oviposition period showed a significantly negative response, being shortest at 25°C (2.5 days). Adult longevity was significantly affected by temperature, being 20 days at 8°C and 6.8 days at 25°C. Egg hatch and development in the laboratory was linearly and positively related to temperature over the range of 2° to 20°C, ranging from 39.9 days at 5°C to 6 days at 25°C. The lethal limit for egg viability was 25°C. The theoretical threshold for egg development was calculated to be 2.79°C. Storage of eggs at temperatures of 2°C for periods in excess of 10 days had a significant effect on the percentage of eggs hatching. The significance of these findings in implementing control operations is discussed.

In India the cultivated oyster mushroom Pleurotus sajor-caju (Fr.) Singer is attacked by the larvae of two species of Phoridae, Megaselia pleurota Disney sp. n. and M. scalaris (Loew). The new species is described. Biological data and damage symptoms are reported for both species. Serious economic damage is also caused by a bacterium associated with M. scalaris. The identities of the two Megaselia species, previously reported attacking this fungus, are called into question.

Lutzomyia longipalpis (Lutz & Neiva), the vector of American visceral leishmaniasis (AVL), is much more abundant in animal sheds than in houses on Marajó Island, Pará State, Brazil. This difference in abundance is known not to reflect host preference. We show here that it also cannot be explained in terms of variable trapping efficiency, or insecticide application, and we exclude animal sheds as important daytime resting sites. In experimental sheds, the number of L. longipalpis increased markedly with the openness of the walls, though artificially large aggregations of flies could be generated in closed houses by using caged flies and hosts as attractants. We conclude that L. longipalpis tend to congregate at sites outdoors, including animal sheds, because these are the places where leks can most easily form on abundant, stationary (sleeping) and accessible hosts. These results help to explain why the seroprevalence of Leishmania chagasi infection is generally much higher among dogs than humans. They also indicate that human exposure to sandfly bites varies with the quality of house construction.

Although Culiseta morsitans (Theobald) is a common Holarctic mosquito very little is known about its biology so many aspects of its life-history were studied, mainly in southern England, from 1964–1987. More limited observations were made in the south on the coastal Culiseta litorea (Shute). Both species laid an average of 109 eggs as an egg raft deposited on wet mud and leaf litter. At high humidities C. morsitans eggs can remain unhatched and viable for many months. Populations of both species overwinter as fourth instar larvae, pupation occurs in April and adults start emerging in early May. The adult season lasts until September or October. Both species feed principally on birds. Serological tests, however, on blood-engorged females show that a few feed on humans, although none has been caught in human bait collections. Light-traps are not very effective in sampling adults, although a few were caught in them, as they were in non-attractant suction traps. The relative sizes of adult populations of both species were monitored in most years from 1964–1980 on Brownsea Island, Poole Harbour, England, and showed a marked decline in the proportions of C. litorea, but there was a resurgence of this species after eight years, when the population again crashed.

Multiple mark-release-recapture experiments were carried out on females of three anthropophilic populations of Aedes simpsoni (Theobald) complex at Nkokonjeru and Bwamba in Uganda to determine and compare the population size, survival rates and longevity of the adult stages. There were high recapture rates (26.23%, 2 7.42% and 28.28%) at the different sites. The population sizes, estimated by Jolly's stochastic method for the three sites (465, 561 and 675 female mosquitoes) were not significantly different, neither were the survival rates of the females (0.6026, 0.7145 and 0.8152). Other parameters estimated for the three populations were also similar. Population size estimates by Jolly's stochastic model and the simple Lincoln Index methods were not in agreement. The other method over-estimated population size. Since the estimated parameters for the Nkokonjeru population are similar to those of the Bwamba populations, there is a potential for the transmission of yellow fever virus to the human population at Nkokonjeru, as at Bwamba.

Detailed studies on the immature stages of the sorghum head bugs, Eurystylus immaculatus Odhiambo and Creontiades pallidus Rambur, were carried out in the laboratory at Samanko, Mali, during November 1991 to March 1992, and January to April 1993, and in the field in October 1993. Eggs of both species were laid in maturing sorghum (Sorghum bicolor) grains. The egg incubation period was 4–7 days in E. immaculatus, and 5–7 days in C. pallidus. There were five nymphal instars in both species. The total nymphal period was 6–11 days in E. immaculatus and 8–14 days in C. pallidus. The durations of first, second, third, fourth and fifth nymphal instars were 1–3, 1–2, 1–2, 1–3 and 1–3 days, respectively, in E. immaculatus, and 1–3, 1–2, 1–3, 2–3 and 2–4 days, respectively, in C. pallidus. All the immature stages of E. immaculatus are described and sketched.

Three new trapping devices (Ml, M2 and M3 traps) were tested and compared with current trapping devices (the F3 and the Epsilon traps) for tsetse flies (Glossina spp.) in Zimbabwe. The most effective was the M3 trap which caught 80% and 73% more male and female G. morsitans Westwood and 110% and 39% more male and female G. pallidipes Austen, respectively. The mean catch for the standard Epsilon trap which was not so effective was six male G. morsitans, 24 female G. morsitans, 76 male G. pallidipes and 199 female G. pallidipes.

The intergenic spacer region of the rRNA cistron was used as a molecular fingerprinting probe to study clonal diversity in Schizaphis graminum (Rondani). A high degree of clonal diversity was found in overwintering populations on wheat from Kansas, Texas and Oklahoma. Out of 184 individuals tested, 132 unique maternal lineages wereidentified. Overall, clonal diversity of overwintering populations was no less than in spring and summer populations. However, in some fields there were more instances where individuals of the same genotype were identified. By partitioning the total population diversity into various sampling components (fields, counties and states), 93.1% of the total diversity was found among individual S. graminum within fields. Overwintering of many genetically distinct clones as parthenogenetic morphs is one mechanism by which clonal diversity is maintained in populations of S. graminum. The incidence of clonal diversity further substantiates the importance of the S. graminum holocycle for generating genetic heterogeneity in the USA.

Some physical and biological factors affecting the abundance of larvae and pupae of the Aedes simpsoni (Theobald) complex, in leaf axils of different plants at several locations in Uganda, were investigated during the rainy and dry seasons. The mean number of axils per plant, axils containing larvae and pupae, and the mean number of larvae and pupae per ml of axil water all varied between seasons and locations. The percentage of axils containing larvae and pupae increased with volume of water in the axils of the different plants. The mean number of larvae and pupae per axil containing water also increased with water content of the axils. There was more water in the axils during the rainy than during the dry seasons. The mean temperature of water was lower in Xanthosorna sagittifoliurn (20.4°C) and Colocasia esculentum (22.1°–22.7°C) than in those of banana (25.0°–27.2°C) and this affected developmental rates of larvae and pupae. The indices of association between larvae and pupae of the A. simpsoni complex and Malaya taeniarostris (Theobald) did not indicate competition and there was some habitat segregation between them. The volume and temperature of water in the axils appeared to be the major factors affecting larval and pupal abundance of A. simpsoni in the axils.

The resistance of two melon lines (CHI-7 and BUS-7) selected for resistance to the carmine spider mite, Tetranychus cinnabarinus (Boisduval), and of the susceptible line (NY), was studied under field and laboratory conditions. Significant differences among lines were observed at different growth stages. Throughout the season, the resistant lines had reduced populations of mites, 35–100% lower on CHI-7 and 25–100% lower on BUS-7, compared with the susceptible line NY. Laboratory evaluation of antibiosis to the mite at different plant growth stages showed that on CHI-7 and BUS-7 mite fecundity was reduced by 29–60% and 43–83%, respectively.

Larvae of the Manchurian catalpa shoot borer Sinomphisa plagialis (Wileman) mainly damaged young shoots of Manchurian catalpa (Catalpa bungei) and ovate catalpa (Catalpa ovata). The typical symptom was production of spindle galls on damaged parts of shoots or branches, usually confined to seedlings, vigorously growing shoots, twigs and branches, as well as young trees below 3 m in height. Feeding occurred from early April to late October. In the Jiaodong peninsula, where there were one to two generations in a year, whereas in the mountainous area of central and southern Shandong, there were always two generations. Larvae had five instars. The longevity of adults was 3–11 days; eggs of the summer generation 7–9 days, overwintering generation 4–6 days; larvae of the summer generation 42–48 days; pupae of the summer generation 13–16 days, of the overwintering generation 22–26 days. Most overwintered in the pith as fifth instar larvae.

Radar, aerial netting and ground sampling were used to study the autumn migration of Nilaparvata lugens (Stål) in Jiangsu Province in east central China. Emigration of macropterous adults increased from late August until late September as the main rice crop matured and was harvested. In early and mid September, the resulting windborne migrations carried the planthoppers mainly towards the west, although the migration directions ranged (within the western sector) from south to north. By late September, however, displacements were predominantly to the south-west on the then prevailing north-east monsoon winds: migration was particularly rapid when the north-easterlies were reinforced by typhoons. Although in late September such movements to more southerly latitudes are essential for the survival of the planthoppers' progeny, we found no definite evidence for preferential emigration on winds blowing towards the south. There were, however, indications that when winds towards the north occurred, the duration of migratory flight was curtailed. Irrespective of any possible preference for migration on northerlies, a large proportion of the N. lugens population would normally be carried in an adaptive southwards direction, because the advent of the north-east monsoon occurs at a time when the number of flight-ready planthoppers approaches its peak.

A technique for initiating artificial strikes on sheep using eggs or larvae of Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) under controlled conditions is described. A liver based implant provides protein for initial larval development. The technique has been found to produce viable strikes more reliably than other currently-used methods for the purpose of screening insecticides in controlled experiments.

The numbers of insects colonizing the dung of cattle injected with the anthelmintics ivermectin or moxidectin were compared with the colonization of the dung from control animals given no treatment, in a blind field trial. Dung was collected 2, 7, 14, and 21 days after dosing and set out in a randomized grid of standard 2 kg pats. Pats were retrieved from each of the three groups group after 7, 14, 21 and 42 days in the field for analysis of insect fauna. There were no significant differences in the number of adult Aphodius spp. (Coleoptera: Scarabaeidae) found in the dung from the three treatment groups with either time of exposure in the field or time after treatment, showing that adult beetles were attracted to all pats equally. However, dung from animals treated with ivermectin prevented the development of larval Aphodius spp. for at least 7 days after treatment. In contrast, the dung from animals treated with moxidectin supported the development of Aphodius spp. at all stages after dosing, as did dung from control animals. There were no significant differences in the number of cyclorrhaphous Diptera larvae in dung from control or moxidectin-treated animals. In contrast, such larvae were largely absent from the dung collected from ivermectin-treated cattle for up to 14 days after dosing. The results show that moxidectin is less toxic to dung-inhabiting insects than ivermectin following standard injection treatment. The results are discussed in relation to the effects of anthelmintics on non-target pastureland insects.

Ceroplastes sinensis Del Guercio is a pest of commercial citrus in Australia and has been recorded from New Zealand, southern Europe, northern Africa, North America and Mexico. Its distribution is mainly temperate and it is more restricted climatically than previously believed. Uncertainty concerning the place of origin of C. sinensis has thwarted previous attempts at biological control. In the present study, a novel and cost-effective approach using cladistic estimates is demonstrated to determine the place of its origin. Cladistically derived phylogenies are commonplace for many organisms, but the method has not been used before to predict the area of origin of a cosmopolitan pest. Cladistic analysis of the wax scales predicts a native range for C. sinensis within Central or South America. This prediction appears to have been confirmed by the recent discovery of heavily parasitized individuals of C. sinensis in Argentina. The cladistic analysis also allows prediction of the geographical origin of three other widespread wax scale speries:Ceroplastes ceriferus (Fabricius) may be of Neotropical origin, C. rubens Maskell and C. rusci (Linnaeus) are probably native to the Afrotropical region. The approach used has wide implications because the native areas of many other economically important pests are still unknown or uncertain.

Genetic variability in four polymorphic loci and variation in phenotypic plasticity in relation to the relative size of wings, were compared and contrasted among eight local populations of Sitonasulcifrons Thunberg from the Czech and Slovak republics. The distances between localities from which samples were taken were between 49 and 492 kilometres. The results demonstrated that: 1. The variability between populations was 5.5% and the other 94.5% of the total variability was realized within populations. 2. Significant differences in allozyme frequencies among populations existed when distances were more than 100 km. A similar trend was also found in variability of relative wing size in males among populations when distances were more than 200 km. 3. Overall, a significant deficiency of heterozygotes in relation to Hardy-Weinberg predictions existed from all samples. The results support the idea that, at least inagricultural areas, gene flow in S. sulcifrons does not seem to be strong enough to stabilize one large interbreeding population in distances over 100 kilometres.

The effects of nine pesticides commonly used in citrus orchards were tested on adults, larvae and pupae of the parasitoid Eretmocerus debachi Rose & Rosen in the laboratory. All pesticides caused immediate mortality to adult parasitoid females and significant losses in efficiency, if applied to larvae of E. debachi in its host Parabemisia myricae (Kuwana). Only the fungicide captan and the insecticide Mercathion (malathion) were slightly harmful and harmless to the parasitoid larva. Gramoxone (paraquat), Dursban 4 (chlopyrifos-ethyl), Mercathion and Supracide (methidathion) were harmful to E. debachi pupae, while five other pesticides were only moderately harmful or harmless.