In host specificity tests using 81 plant species from 27 families, an undescribed Chrysolina sp. completed its development only on Chrysanthemoides monilifera, a serious weed of native vegetation in Australia. Minor exploratory feeding, mostly by adults, occurred on 35 plant species. The Chrysolina sp. is restricted to the eastern Cape Province of South Africa where it occurs on Chrysanthemoides m. pisifera, a subspecies not yet recorded in Australia. Chrysanthemoides m. monilifera and C. m. rotundata, both naturalized in Australia, were accepted as hosts by Chrysolina sp., but adult emergence was lower on the latter subspecies. A climate comparison between a site location for Chrysolina sp. and stations within the Australian distribution of Chrysanthemoides monilifera has identified potential release sites that may be suitable for the insect. Chrysolina sp. was approved for release in Australia in 1989 and releases were initiated in 1990.

Field experiments were conducted in the dry season of 1985–86 and the first and second rainy seasons of 1986 at Ibadan, Nigeria, to assess the level of damage and yield reductions caused by Eldana saccharina Walker to maize. Grain weight per plant in artificially infested plots was up to 36% lower than grain weight per plant in insecticide-protected plots. Artificially infested plots had significantly lower 100-grain weight than insecticide-protected ones. The regression coefficient obtained from covariance analysis revealed that 100-grain weight decreased by 0.125 g for each unit increase in the percentage of the stem tunnelled. Infestations of E. saccharina were found to increase significantly the incidence and severity of stalk rots.

This study demonstrates that only a proportion of Lucilia cuprina (Wiedemann) females, which have fed exclusively on sheep dung collected from spring improved pastures, are able to mature a complement of oocytes at the cost of high resorption. Fifty percent of females developed mature oocytes after 11 d of continuous feeding on sheep dung. After 14 d feeding, 80% of females had matured an average of 143 eggs. Females given ad lib access to sheep's liver developed mature oocytes within 2–3 d feeding, producing an average of 223 eggs. Results show that sheep dung is a resource used by L. cuprina adults, but by itself appears to be a poor source of protein for field females to mature oocytes. Females given continuous access to dung collected from sheep 18 h after being drenched with ivermectin, were virtually unable to develop oocytes beyond the resting stage after 10 d feeding. Female adults in particular, became distended with fluid over successive days feeding and both sexes suffered significantly higher mortality compared with adults fed on untreated sheep dung. Knowledge on the feeding frequency and amounts of sheep dung ingested by L. cuprina adults may enable an assessment of the potential for manipulation of ivermectin treatment in a control strategy.

Tick populations were observed on zebu cattle (Bos indicus) over an 18 month period at Patiko in northern Uganda. Monthly collections were made of all stages of ticks from five cattle and six sheep (Ovis aries). Collections of adults of Rhipicephalus appendiculatus Neumann were also made from the ears of about 30 cattle on several occasions. The species recorded on cattle, in order of decreasing abundance, were R. appendiculatus, Amblyomma variegatum (Fabricius), Boophilus decoloratus (Koch) and R. evertsi evertsi Neumann. Far fewer ticks were collected from the sheep. The adults of R. appendiculatus were randomly distributed over the herd. There was a distinct seasonal incidence of R. appendiculatus and A. variegatum on their hosts, which could be related to rainfall and to the emergence of new cohorts during the long rainy season. In addition, adult females of R. appendiculatus were collected daily off the ears of cattle at Entebbe following an infestation with 200 adult males and females. Measurements of the growth of the ticks were used to define the sizes of ‘standard’ ticks which would complete engorgement in the following 24 h. Such ticks provide a means of sampling to estimate the number of ticks engorging daily. Comparison of the frequency distributions of each stage and species in the Patiko collections were then used to infer the sizes of standard ticks for other species.

The pattern and cause of mortality of the early stages of Helicoverpa armigera (Hübner) on cotton was investigated in both field and glasshouse situations for two seasons. In 1987, egg losses were high (32–88%) over days 1–3 following oviposition, more so from the lower than upper leaf surface. The mortality of first instar larvae was 93–100% over days 4–5 following oviposition, and losses were higher from seedling stage than squaring cotton. Wind, rain (or watering), aerial predators, dispersal of first instar larvae, and host plant effects (including leaf orientation) were important mortality factors. In 1988 trials, egg losses over days 1 to 3 after oviposition on plants in glasshouse and field situations, respectively, were 0–1% and 5–6% due to changing leaf orientation alone; 4–22% and 16–32% due to rain/watering and changing leaf orientation combined; 14–31% and 12–31% for wind and changing leaf orientation combined; and 4–38% and 23–52% for the combination of wind, rain/watering and changing leaf orientation. Mortality of first instar larvae on day 4 was 32% and 29% on plants in glasshouse and field, respectively, from which the action of such mortality factors had been excluded. Mortality on plants with changing leaf orientation alone was 30% and 68%, with rain/watering and changing leaf orientation combined 48% and 74%; with wind and changing leaf orientation combined 40% and 63%; and with all factors combined 45% and 69%, respectively. The highest losses (of eggs) occurred on day 1 after oviposition, and similarly for first instar larvae on day 4, which coincided with hatching.

The thermal preference of adults of the reduviid bug Triatoma infestans (Klug) was investigated along a temperature gradient by means of video recording. The preferred temperature varied with a daily rhythm, reaching the highest value at the onset and the lowest at the end of the dark phase. The daily range of preferred temperatures depended on the starvation level. After feeding it was about 28–29°C, and after 12 days of starvation 25–26°C. The number of eggs laid showed a bimodal pattern, with maxima at 29°C and 26°C. Along a gradient of relative humidity, the bugs were always found around 40% r.h.

Toxoptera victoriae sp. n. is described from Hong Kong. The economic importance of the genus Toxoptera is discussed. Separate keys are provided to adult and first instar larvae of the species of Toxoptera.

In undisturbed annual pasture in a Mediterranean-climate region of Australia adults of the whitefringed weevil, Graphognathus leucoloma (Boheman), were present from summer to early winter (December–June), with upsurge in numbers of first instar larvae only occurring after the rains began in April. The G. leucoloma population was predominantly first instar larvae in high abundance throughout the winter period (May–August). Larval growth, with high mortality, occurred in the spring period (September–January). The survival of eggs during the dry summer when adults were most abundant, although only at times of unseasonal rainfall, indicated that low larval recruitment at that time resulted primarily from the absence of high-quality legume food essential for oogenesis. It was inferred that most larvae arose from heavy oviposition by the few adults present in autumn when rainfall germinated annual legumes. A steady year-round abundance of late-instar larvae indicated that not all individuals completed their development in the one year.

The durations for development for immature stages of the fruit piercing moth, Eudocima salaminia (Cramer), were determined at constant temperatures ranging from 15°C to 27°C and at ambient temperatures at a field site in southeastern Queensland over a 16 month period. At constant temperatures average heat requirements for: 50% eclosion of eggs were 62.4 day-degrees above 11°C, development of larvae to pupation were 246 day-degrees above 12°C, development of pupae to eclosion were 233 day-degrees above 12°C. For each stage there was no difference between day-degrees calculated at constant temperatures or at those in the field indicating no diapause in the immature stages. For adults, temperatures below 16°C during the activity period after dusk prevented feeding, mating and oviposition. Failure of E. salaminia to overwinter in south-eastern Australia in most years, was explained by the effects of low temperatures on egg hatch, larval, pupal and adult survival, reduced adult feeding, mating and cessation of oviposition.

The spatial distribution of five lepidopterous pests, Sesamia calamistis Hampson (Noctuidae), Eldana saccharina Walker (Pyralidae), Spodoptera exempta (Walker) (Noctuidae), Mussidia nigrivenella (Ragonot) (Pyralidae), and Cryptophlebia leucotreta (Meyrick) (Tortricidae), on maize in West Africa is described using Taylor's power law and the relationship of proportion of infested plants to the mean density. All five species showed a highly aggregated distribution, with Taylor's indices of aggregation ranging between 1.23 for C. leucotreta and 1.52 for Sesamia calamistis. Enumerative and binomial sampling plans that incorporate Taylor's power law are proposed to estimate mean densities of S. calamistis, C. leucotreta and the species complex consisting of E. saccharina, M. nigrivenella and Spodoptera exempta which showed similar spatial distributions, with a predefined reliability level.

The length of the intergenic spacer in the rRNA cistron varied within and among individuals of Schizaphis graminum (Rondani). Spacer lengths did not vary among offspring of a single maternal lineage (clone). The intergenic spacer was used as a molecular fingerprinting probe on individual aphids and to study spatial and temporal distributions of clones. A spatially nested sampling design was used in wheat and sorghum to estimate numbers of clones among aphids on leaves, among leaves on plants, among plants in fields, among fields in counties, among counties, and among dates. Each level of nesting added a level of clonal diversity to the entire population. 82.3% of the total population diversity was found among aphids on one sorghum leaf. Sampling additional leaves increased diversity slightly (5.4%), whereas plants (0.9%), fields (0.6% to 3.6%), and counties (1.2%) added very little. Sample dates contributed the highest increase in diversity (11%). Diversity rose and fell in wheat along with aphid numbers but remained constant in sorghum. Little variation in Mahalanobis distances could be explained by geographic distances. No genotypes were unique to any field, county, crop, or year. Kansas populations are made up of a large mixture of genetically diverse clones that recolonize wheat and sorghum each year. Sampling many plants, fields, or counties is an ineffective way to increase clonal diversity. Plant breeders developing crop resistance to S. graminum can expect plant entries to be exposed to most of the genetic diversity present in Kansas populations regardless of location.

To study life cycle variability in Rhopalosiphum padi (Linnaeus), the responses to short days (L:D 10:14) of 70 clones were tested at two temperatures (10°C and 15°C) in the laboratory. Three clones originating from spring populations on the primary host, bird cherry (Prunus padus), were holocyclic, producing gynoparae and then males in the second generation under experimental conditions. Of the other clones, all originating from Gramineae, 78.5% were anholocyclic and 21.5% androcyclic (male-producing) at 15°C, but at 10°C only 12.7% were anholocyclic, 82.6% were androcyclic, and 4.7% showed an ‘intermediate’ response (i.e., some of the alate females produced both sexual and parthe-nogenetic offspring). There was considerable interclonal and inter-individual variation in the numbers of males produced by androcyclic clones. These results are discussed in relation to field studies on R. padi in Britanny, which indicate that 1. primary hosts are rather rare, but nevertheless commonly develop spring infestations; 2. anholocyclic genotypes are regularly decimated every few years by severe winters. It appears that the preponderance of androcyclic clones is important for the maintenance of life cycle variability.

Field studies in Zimbabwe elucidated how trees might be enhanced as baits for controlling Glossina morsitans morsitans Westwood and G. pallidipes Austen. Catches from electrocuting devices at the bases of trees were near nil when sampling tsetse flies landing on the trunk but much greater when sampling them flying within 1 m of the trunk. Catches increased 5–8 times when 2 m2 of the trunk were blackened and given odour of acetone, 1-octen-3-ol, 3-n-propyl phenol and 4-methyl phenol, but were still only ca. 30% of the catches from an odour-baited, free-standing, 1 × 1 m screen of black cloth. The upright trunk of real and model trees hindered their attractiveness but leaves and branches 5 m above ground had no clear effect. Real and artificial stumps of trees were as effective as the screen if they were 1 m2, compact and sharply outlined. The practical and biological implications of the results are discussed, with particular reference to the use of insecticide-treated netting with modified tree stumps as baits for control.

Data from dung-baited pitfall traps show that dung beetles (Coleoptera: Scarabaeidae) do not discriminate against dung from sheep or cattle treated with avermectin. On the contrary, for a period post-treatment, dung from animals treated with avermectin attracted more beetles than dung from untreated animals. This effect was more marked with cattle dung than with sheep dung. The period of enhanced attractiveness of sheep dung was restricted to dung produced during the first day after treatment, whereas with cattle dung, the effect was still evident in faeces produced 25 days after treatment. Cattle dung produced from 3–25 days post-treatment caused 100% mortality in newly hatched larvae of the bushfly, Musca vetustissima Walker (Diptera:Muscidae). In dung of day 35, mortality was 93.6%. Dung collected from sheep from 1–6 days after treatment also caused 100% mortality of fly larvae, but by day 28, no toxic effects were detectable. Field observations on the colonization of cattle pats confirmed the enhanced attractiveness of dung from treated animals and suggested that departure rates from treated dung were lower than those from untreated dung. Treated pats supported higher beetle populations than untreated pats and burial was more rapid. The potentially serious implications of the enhanced attractiveness of avermectincontaminated dung are discussed in relation to the survival of dung beetle communities.

In mixed cocoa-coconut palm plantations in Malaysia the palm spadices provide large, stable nesting sites for Dolichoderus thoracicus (Smith) in contrast to impermanent sites on cocoa and on the ground. D. thoracicus and the arboreal leaf-nesting Oecophylla smaragdina (Fabricius) both benefit from the mixed system which also provides a more stable food supply from honeydew-producing Homoptera. A scoring method showed that about 50–200 O. smaragdina or 200–2000 D. thoracicus on a cocoa tree can protect it effectively from Helopeltis theobromae Miller (Hemiptera: Miridae). The relatively greater efficiency of O. smaragdina as a biological control agent is associated with its actively dispersive predatory behaviour in contrast to the localized concentration of D. thoracicus workers at sites such as cocoa pods where it tends honeydew-producing Homoptera, and where it acts largely by deterring H. theobromae. Despite its biological control potential, the painfully biting O. smaragdina, unlike D. thoracicus, is normally considered unacceptable to plantation staff. Nevertheless it should be recognized as valuable in integrated pest management of cocoa pests especially where D. thoracicus is difficult to establish.

Targets of black cloth with or without flanking netting panels (ca. 1 m tall × 1.7 m) baited with acetone (130 mg/h) and 1-octen-3-ol (0.5 mg/h), coated with deltamethrin suspension concentrate and deployed at 4/km2, produced a decline of 3% per day in the apparent density of the tsetse fly Glossina morsitans centralis Machado in 500 km2 of the Western Province of Zambia. Flies were eradicated in a year as evidenced by the absence of catches from flyrounds and traps and the elimination of the transmission of trypanosomiasis. The promise of the target technique is confirmed but the need for its further development is emphasized.