Predatory arthropods on cabbage terraces were studied by square flooding and by pitfall trapping in January 1992, following a transect through the Cordillera Region of Luzon, with decreasing numbers of insecticidal sprays per year. Predator numbers were sampled along this transect per 4 m2 and with 15 pitfall traps per site. The dry biomass of predators was also measured. The four sites studied were classified as two pairs, one with high input of insecticides and low predator numbers, low biomass and diversity, the other with low insecticidal input and high predator numbers, high biomass and diversity. The number of ant (Hymenoptera: Formicidae) genera per 15 pitfall traps increased along the transect, showing that ants might be used as indicators of the insecticidal intensity for growing vegetables in the Luzon Cordillera Region. Compared with Europe, the potential abundance and diversity of predators in the Philippines proved to be very high. The reasons for the large differences between sites concerning abundance and diversity of predators are discussed, together with conclusions drawn from the findings presented.

Smallholder crops (sunflower, maize, sorghum and cotton) were grown in experimental plots at seven sites, representing different agricultural zones of Kenya, over four seasons. Helicoverpa armigera (Hübner) (formerly Heliothis armigera) only occasionally achieved population densities sufficient to cause obvious damage to the crops, and was virtually absent from the coastal sites. At the inland sites, infestation and mortality levels varied greatly. Information is presented on the incidence of H. armigera, and the identity, distribution and frequency of its common parasitoids and (potential) predators, sampled in the experimental plots. Trichogrammatoidea spp., egg parasitoids, and Linnaemya longirostris (Macquart), a tachinid late-larval parasitoid, were the most common parasitoid species, but total percentage parasitism was rather low. Of the large complex of predators, only anthocorids and ants (predominantly Pheidole spp., Myrmicaria spp. and Camponotus spp.) were sufficiently common and widespread to be of importance in suppressing H. armigera. The abundance of predators fluctuated widely between sites, but anthocorids were most abundant at the western sites.

Video observations were made of tsetse flies (mainly Glossina pallidipes Austen) as they approached, responded to and left a vertical (1 m square) black target in odour plumes of acetone, or a 4:1:8 mixture of octenol:propylphenol: methylphenol, or acetone plus this “4:1:8” mixture, or in no odour. No differences in mean flight speed or turn size in any of these situations were detected. With the odour source 5 m upwind of the target, the flight tracks of tsetse arriving at and leaving the target were significantly biased towards upwind, highly so when 4:1:8 was present, marginally so in acetone alone. With the source 10 m upwind, the same biases were still present but weaker. Circling flights around the black target were more frequent in acetone plus 4:1:8 than in no odour (26% vs 15%), but in either odour alone were only just significantly more than in no odour. Upwind turning at the target was more frequent (25% vs 17%) in acetone alone that in no odour (though not in 4:1:8 alone). It is concluded that 4:1:8 elicits an upwind anemotactic response comparable in strength to that in CO2, and that acetone elicits a similar response more weakly, but may be more involved in potentiating visual responses.

Comparisons of infestation and damage levels by the cotton bollworms, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), Earias vittella (Fabricius) and E. insulana (Boisduval) (Lepidoptera: Noctuidae) were made in cotton fields treated with pheromones + insecticide, insecticides only, and untreated control plots, in Pakistan during the 1991 cotton season. Early to mid season control of these three pests by mating disruption in the pheromone + insecticide treated plots meant that an average reduction of 3.5 applications of insecticides was achieved when compared with the insecticide only treated plots to control the cotton pest complex. Night observations showed that there were far fewer adult moths visible in the pheromone + insecticide treated plots than in insecticide only treated plots. Adults of both sexes were much less active and did not mate as frequently as adults in the insecticide only plots.

Two weevil species, Ceutorhynchus geographicus (Goeze) and C. larvatus Schultze, feed on Echium plantagineum (Boraginaceae) in southern France. This paper shows that they do not compete for resources in the host's native environment. Niche overlaps of the two weevils were measured using the proportional overlap measure and Morisita's original index. The two species showed significant overlap in niche requirements during the egg and early larval stage. During the final two larval instars, larvae feed on different parts of the plant, C. geographicus in the tap root and C. larvatus in the root crown. Spatial separation in niche requirements is augmented by a temporal separation, C. larvatus emerging in the field about one month earlier than C. geographicus. In Europe and in Australia, to which E. plantagineum has been introduced and has become a serious weed, the host-plant has an extended germination period during the autumn. The differences in emergence times of the two species mean that their niches are separated both in time and in space. Should the two species be released into Australia they would not compete for resources. They may, however, be able to displace other species of the stemfeeding guild that are also proposed as candidates for the biological control of E. plantagineum.

The inability to distinguish the females of East African Synphlebotomus spp. (P. martini Parrot, P. vansomerenae Heisch, Guggisberg & Teesdale and P. celiae Minter) was a major constraint on epidemiological studies of visceral leishma niasis (VL) in the region. An intensive morphometric study of two sympatric Synphlebotomus spp. (P. martini and P. celiae) in a VL focus of southern Ethiopia based on both isofemale broods and wild-caught parent specimens (identified by their male progenies) showed that laboratory-bred females were separable by eight morphological characters, but only two (labrum length and labrum length/wing length ratio) successfully distinguished the wild-caught parent females of the two species; the latter were used to identify wild-caught Synphlebotomus females from southern Ethiopia (Aba Roba) during subsequent epidemiological studies. A further difference between the two species was seen in the length of the spermathecal ducts.

A juvenile hormone mimic (pyriproxyfen) was used with odour-baited targets to assess its suitability for controlling tsetse flies (Glossina spp.). In August 1991, 41 odour-baited targets identical to those used with insecticide in tsetse control operations, were each treated with 4 g of pyriproxyfen and deployed near Rekomitjie Research Station, Zambezi Valley, Zimbabwe, in a 12.3 km2 block of woodland habitat of Glossina morsitans morsitans Westwood and G. pallidipes Austen. After three months, emergence rates from puparia of the two species collected in the block fell to 34% and 20% of control levels; 50 and 70%, respectively, of puparia of the two species collected were found, on dissection, to show arrested development. Changes in mean ovarian age and wing-fray category in the tsetse population during the trial were due partially to the pyriproxyfen and partially to high mortality, in the larval/pupal stages and in young adult flies, which occurs each year in the hot/dry season. Chemical analysis of cloth samples indicated that after four months 68–85% of the pyriproxyfen had been lost, a large proportion apparently dripping off the bottom of the target. If the technical problem of persistence can be solved pyriproxyfen could substitute for pesticides in target-based tsetse control operations.

Between 1987 and 1989, three predatory beetle species (Chilocorus bipustulatus (Linnaeus), C. infernalis (Linnaeus) and C. cacti (Linnaeus)) (Coleoptera: Coccinellidae) and two predatory mite species (Hemisarcoptes coccophagus Meyer and H. cooremani Thomas) were imported and released for the biological control of armoured scale insects (Hemiberlesia rapax Comstock, H. lataniae Signoret and Aspidiotus nerii Bouché) on kiwifruit and shelter trees in New Zealand. Hemisarcoptes coccophagus has established on Hemiberlesia lataniae infestations on Lombardy poplar (Populus nigra var. Italica) shelter trees at three sites. Detailed studies at one of the release sites over a period spanning nine to 24 months after release, showed that densities of Hemiberlesia lataniae in samples with mites fell to less than 20% of the level in control trees. Assessment of the dispersion characteristics of the mite suggested that the adults are repelled by the presence of other mites on a host. Hemisarcoptes coccophagus can use two species of New Zealand ladybirds (Scymnus fagus Broun and Halmus chalybeus Boisduval) for phoresy. Hemisarcoptes coccophagus spread naturally to the control trees between 20 and 24 months after release, though the means of dispersal between trees is not known.

The Rothamsted Insect Survey has kept records of aerial aphid activity using suction traps since 1965. Previous work has shown that, for certain species, there is a linear relationship between the date of first record in the trap each year and the mean temperature during the preceding winter. This paper describes and evaluates a more complex technique which relates the date of first record to a range of weather variables over 28 winter time periods. The technique uses principle components analysis to remove correlations between weather variables before these are regressed on the date of first record. Data from 1966 to 1988 inclusive are used to generate models to predict the date of first record of Myzus persicae (Sulzer) at Rothamsted, and the predictive values of models using both simple and multiple regression are assessed using data from 1989 to 1992. The accuracy of the multiple regression models was no greater than that of the simple regression models during these years. However, the multiple regression approach identified relationships with other variables for time periods when the correlation with mean temperature was weaker and may therefore be more widely applicable.

Zygogramma bicolorata Pallister was introduced for biological control trials against the weed Parthenium hysterophorus (Asteraceae) in India. The insect entered diapause over an extended period of time between July and December in Bangalore. Diapausing adults burrowed into the soil, and emerged in May–June with the commencement of monsoon rains. Percentage diapause increased over time, peaking at 72% during November. Non-diapausing adults were capable of breeding, under laboratory conditions, during the winter. Some adults bred both before and after diapause, during two consecutive years. Soil moisture played an important role in providing the conditions for burrowing or emerging from the diapause chambers. The studies also showed that diapausing adults had to be exposed to the high summer temperatures, for termination of the diapause. It was possible to break diapause by continuous exposure to 30°C, 35°C and 40°C for 22 days, nine days and 10 hours, respectively, during February–March, about three months after its inception. This method can be used to initiate mass multiplication for carrying out releases early in the season.

The effect of cyromazine on the mechanical properties of the larval integument of Lucilia cuprina (Wiedemann) was measured using third instar larvae 2–3 h after moulting placed on liver containing 1 ppm cyromazine. Cuticle stiffness (Δ force (N)/δ strain) was approximately 20–30% higher in treated larvae (relative to controls) after 6–10 h treatment, after which time stiffness decreased to levels well below controls. Larvae placed on 1 ppm cyromazine early in the second instar also showed a short period of slightly elevated cuticle stiffness (relative to controls) after 3–5 h treatment. Third instar larvae placed on cyromazine-treated diet for 8 h then transferred to normal diet showed the same short period of elevated stiffness (at 6–10 h) followed by rapid decrease in stiffness to levels well below controls and greatly reduced growth as larvae fed cyromazine continually. A slight increase in cuticle stiffness appears to be only an early and temporary effect of cyromazine poisoning in L. cuprina. These results are discussed in relation to the previously documented effects of cyromazine on the mechanical properties of the larval cuticle of Manduca sexta (Linnaeus).

The impact of Sahelian grasshopper species on short cycle pearl millet (Pennisetum glaucum) was studied at two sites in north-west Mali and techniques of crop loss assessment were investigated. At one of these sites an onfarm study was carried out with the co-operation of seven village farmers. The grasshoppers Diabolocatantops axillaris (Thunberg) and Kraussaria angulifera (Krauss) were the principal destructive species, primarily causing grain loss through their feeding upon millet heads. Leaf damage was found to be sustainable to a high level before influencing yield, although direct grain loss through head damage was shown to be an important determinant of final yield. It was concluded that the best means of determining the yield loss attributable to grasshopper attack for late-season patterns of damage was to estimate head damage immediately prior to harvest. In this estimate, heads were assigned to one of ten classes according to the severity of the damage. Studies at a second site demonstrated the existence of a linear relationship between estimates of head damage and actual grain weight loss. On the basis of these findings it is concluded that the average loss of yield incurred as a result of grasshopper attack in the study village, Mamaribougou Freybe, was 25.7% + 3.0, −2.5. A system is proposed by which such village-level crop loss estimates may be undertaken.

The effects of nitrogen and silica application to maize plants on various aspects of the bionomics of the maize stem borer, Sesamia calamistis Hampson, were studied in the laboratory. Increasing nitrogen doses significantly increased larval survival (from 18.7% (control) to 37.3% at 2.25 g N/plant), larval weight (from 49.0 mg (control) to 99.5 mg at 2.25 g N/plant), and female fecundity (from 77 eggs per female (control) to 365 eggs per female at 1.69 g N/plant). A significant, positive relationship was found between moth fecundity and female pupal weight. Nitrogen had no effect on larval and pupal developmental time but increased adult longevity. Intrinsic rate of increase, rm, and the net reproductive rate, Ro, were positively related to leaf and stem nitrogen, while generation time, G, was negatively related. Silica had the opposite effect from nitrogen on larval survival. Increasing silica supply reduced ultimate larval survival from 26.0% (control) to 4.0% at 0.56 g Si/plant. Immature developmental time, larval and pupal weight, pupal survival, female fecundity, egg viability and adult longevity of S. calamistis were not affected by silica application.

Threshold temperatures, growth rates and physiological development times were calculated for the egg, larval and pupal stages of the groundnut leaf-miner, Aproaerema modicella (Deventer), a key pest of groundnut (Arachis hypogaea) and soyabean (Glycine max) in India. The life cycle of Aproaerema modicella required 660 degree-days (DD) above threshold temperatures (12.4°C for eggs, 11.3° for larvae and 14.7° for pupae). A function fitted to the adult longevity and fecundity data describes the effect of temperature and female age on fecundity. Egg production was greatest at 30°C and declined at lower and higher temperatures. Head capsule width measurements indicated that five larval instars are typical in India. The results obtained are discussed in the context of earlier work.

Fourteen wild species of Arachis (Leguminosae) were investigated under field and laboratory conditions to evaluate their effect on the survival and development of the larvae of Spodoptera litura (Fabricius). All of the species studied were observed to be resistant compared to the susceptible control, Arachis hypogaea (genotype TMV2). Overall, the mortality and development of larvae recorded in the field were similar to those recorded for larvae on excised leaves of the same species in the laboratory. When neonate larvae were exposed to excised leaves of A. batizogaea, A. kemph-mercadoi, A. appresipila, A. paraguariensis, A. stenophyla and A. villosa mortality was greater than 94% compared to less than 20% on TMV2. Third stadium larvae lost weight when exposed to both field plants and excised leaves of eight of the wild species, whereas larvae feeding on TMV2 gained weight. When third stadium larvae were fed pulped leaves they gained more weight than when exposed to intact leaves, except in the case of A. chacoensis and Arachis spp. 30007. A penetrometer was used to determine the relative toughness of the leaves. The leaves of most of the wild species were shown to require a greater biting effort for feeding than the leaves of TMV2. There was a negative correlation between toughness of whole leaves and larval development. Observations of larval behaviour indicated that, overall, larvae were deterred from feeding on the leaves of the wild species. Diets containing the chemical extracts of dried leaves of A. kemph-mercadoi, A. paraguariensis, A. appresipila, A. chacoensis, A. glabrata and A. pseudovillosa resulted in low larval weight gain. The physical quality of the leaves and foliar chemicals are implicated as being responsible for the observed resistance. The implications and potential applications of these results are discussed.

Populations of the blowfly Lucilia sericata Meigen in sheep pastures were monitored for three years (1990–1992) using sticky targets. A simulation model, developed previously from detailed analyses of the effects of temperature on the component stages of the life-cycle of L. sericata, was used to predict the pattern of seasonal abundance expected during these years at the temperatures observed. After inclusion of the effects of temperature over each catching interval, the model was able to explain 67%, 52% and 49% of the variance in catch in 1990, 1991 and 1992, respectively. The model was validated by using regression coefficients and constants derived from data collected over previous years to predict the expected catch in the following year. Up to 50% of the variance in catch was explained by this analysis. The results confirm value of the day-degree modelling approach for this blowfly species and suggest that such predictive models may play an important role in the development of strategic control for flystrike prevention.

Following the examination of 53 Lutzomyia spp., seven Phlebotomus spp. and five Sergentomyia spp. (Diptera: Psychodidae) new observations are recorded on the presence of pheromone disseminating structures on the tergites of male phlebotomine sandflies. Descriptions are given of 11 of the species which include structures such as simple cuticular pores in craters, pores with emergent spines, and mammiform papules with or without spiny processes. Pheromone papule distribution on the tergites of Lutzomyia pessoai (Coutinho & Barretto) is plotted and gas chromatography and GC-mass spectroscopy have been used to demonstrate the presence of a diterpene compound similar to a sexual attractant pheromone observed in some L. longipalpis (Lutz & Neiva) populations.

This review examines the recent literature on tsetse (Glossina spp.) metamorphosis behaviour and its regulation. The behavioural events associated with metamorphosis are highly specific and most occur only once during the life of the fly. The review begins with the larva's commitment to metamorphosis and then discusses the behaviour associated with parturition, wandering of the third instar larva, pupariation, pupation and adult eclosion. While certain aspects of tsetse metamorphosis behaviour are common to the higher Diptera, the peculiar reproductive strategy of tsetse has dictated many modifications. Most notable of the tsetse peculiarities are the larva's late commitment to metamorphosis, the contribution by the mother in deciding the onset of the wandering period, the brevity of the wandering period, the involvement of the nervous system in co-ordinating puparial tanning, the tight pack aging of the pupa within the puparium, the long duration of pharate adult development, and the great expansion of the body that occurs following eclosion. A final section discusses the potential for disrupting tsetse metamorphosis.