A procedure for rearing Clavigralla tomentosicollis Stål on dry seeds of cowpea (Vigna unguiculata) is described. Dry seeds produced results for nymphal development and adult oviposition similar to those from fresh pods and fresh seeds, which are more frequently fed on by the insect in nature. The rearing method described here is much more efficient in terms of time and manpower requirements than the widely used method using fresh pods. Furthermore, the dry-seed procedure may be adapted for rearing other hemipteran pod pests of legumes.

The population dynamics of three vectors of rice tungro viruses (RTV), Nephotettix virescens (Distant), N. nigropictus (Stål) and Recilia dorsalis (Motschulsky), were investigated in farmers' fields in the Philippines from 1979 to 1984. R. dorsalis was the most abundant vector species on the rice seedbeds and weed covered levees between rice-growing seasons, whereas N. virescens was the most abundant on the rice crop. Population curves for the three species were similar in the same season, suggesting common population-regulating processes. Adults and nymphs of all three species were present at the sampling site during a four-month fallow period between crops.

Cormiococcus gen. n. is described for C. dieramae sp. n., a mealybug collected in South Africa on the corms of Dierama sp., imported to the Royal Botanic Gardens, Edinburgh, UK. Another mealybug species, Chorizococcus lachenaliae sp. n., is described from the bulbs of Lachenaliae sp., imported from South Africa to the Royal Botanic Gardens, Kew. Chorizococcus bardus (De Lotto) comb. n., originally described from South Africa on bulbs of Narcissus capensis, is transferred from Maconellicoccus Ezzat.

Static tethered flight was used under laboratory conditions to investigate the flight duration of Chilo partellus (Swinhoe). A flight mill was used to measure flight velocity. Mated females flew for a longer time than unmated ones. Females also flew for a longer time than males. Mated females were able to fly and lay eggs alternately for at least three nights in a row. Flight did not affect the number of eggs deposited by females. The results from the flight mill show that the mill is an accurate device to measure flight velocity. The airspeed of C. partellus proved to be 0.9 m/s, and there appeared to be no difference between the flight velocity of mated or unmated males and females.

Larvae of the southern African geometrid moth Comostolopsis germana Prout feed on the shoot apices and axillary buds of Chrysanthemoides monilifera, a serious alien weed of native vegetation in Australia. The insect was found in low abundance throughout the distribution of its hosts, C. incana and C. monilifera, in southern Africa. Larvae were present throughout the year in subtropical Natal, but were absent in winter in the cooler, Mediterranean type climate of Cape Province. In host-specificity tests using 65 plant species from 26 families, Comostolopsis germana completed development only on Chrysanthemoides monilifera monilifera and C. monilifera rotundata. Insignificant, exploratory feeding occurred on Olearia axillaris (Compositae) and pea, Pisum sativum (Leguminosae). In multiple-choice oviposition tests eggs were laid on 41 species, but a strong preference was shown for the foliage and stems of C. monilifera. Larvae grazing the flower buds, pedicels and peduncles of C. monilifera may reduce the reproductive capacity of their host and contribute to its control. Comostolopsis germana has been approved for release as a biological control agent of Chrysanthemoides monilifera in Australia.

Chaetorellia acrolophi sp. n. is associated with some European species of the subgenus Acrolophus of Centaurea. It is a potential biocontrol agent of some Acrolophus species that are adventive noxious weeds in North America. Ch. acrolophi sp. n. is described, and a key is provided to all nine species. The confirmed host-plants, knapweed, starthistles and related plants, belong to the genera Centaurea, Carthamus and Chartolepis (Asteraceae), and these are listed. Available biological data are reviewed, and some details of egg, larval and pupal morphology are described. Host-plant choice tests and canonical variates analysis were used to justify the separation of some species and to help identify some populations. The following nomenclatural changes are made (junior synonyms in brackets): Chaetorellia conjuncta (Becker) is removed from synonymy with Ch. succinea (Costa); Ch. hexachaeta australis Hering is raised to specific status; Ch. hestia Hering (=Ch. nigropicta Hering); Ch. loricata (Rondani) (= Ch. mara Hering and Ch. loricata septentrionalis Hering). Questionable synonyms include: Ch. australis Hering (?=Trypeta hexachaeta Loew); Ch. hestia (?= T. vittata Rondani); Chaetostomella cylindrica (Robineau-Desvoidy) (?= Tephritis algira Macquart, which is removed from Chaetorellia).

Cassava intercropped with cowpea in Colombia had lower numbers of Aleurotrachelus socialis Bondar and Trialeurodes variabilis (Quaintance) per leaf and per plant than did monoculture cassava. These differences persisted for up to six months after harvest of the cowpea. These results are examined in light of the natural enemies hypothesis, which suggests that natural enemies may be favoured in diversified systems, thereby reducting herbivore load. In this regard, the effects of different cropping systems on the whitefly predator Delphastus pusillus (Le Conte) and on the combined action of the parasitoids Amitus aleurodinus Haldeman and Eretmocerus aleyrodiphaga (Risbec) are discussed. D. pusillus displayed a functional responce and was more abundant in monocultures than in intercrops. Predator:prey ratios were similar between treatments and so low that predation appeared to have little impact on whitefly numbers. Parasitism levels of Aleurotrachelus socialis were not affected by crop combinations. The data suggest that the activity of the natural enemies does not explain cropping system effects on cassava whitefly populations.

Apanteles agonoxenae Fullaway and A. orelia Nixon are founded to be conspecific. The valid name for this species is, A. agonoxenae and A. orelia is a junior synonym of it. The species, which is a parasite on the coconut pest Agonoxea argaula Meyrick in the south-western Pacific, is redescribed, its distribution and biology are summarized and attention is drawn to its potential as a biological control agent.

Infestations of Eldana saccharina Walker in South Africa are higher in intensively-grown than in peasant-grown sugarcane, and are worse in water-stressed plants. Although field trials showed negligible increases in the incidence of the pest with applied nitrogen, the degree in which the degree of water stress could not be controlled. Pot-plant trials, in which the degree of water stress was controlled as well as the amount of fertilizer, showed that the combination of nitrogen with stress resulted in increased survival of larvae and greatly increased biomass with shortened development times. Adults did not appear to choose stressed or fertilized plants in preference to normal or unfertilized ones. In every case, whether in the field or in insectary trials, increased infestation levels were associated with increased stalk total nitrogen. Amino acid determinations showed that the balance of individual acids did not appear to alter but that the balance of individual acids did not appear to alter but that glyphosate ripener had a similar effect to water stress, increasing all amino acids together. Infestations in older cane were disproportionately higher than in younger cane, weight for weight, despite reduced levels of stalk nitrogen. This anomaly may be due to the presence of phenolic compounds in younger cane, or in cane tops. Levels of nitrogen are much higher in the feeding sites of the insect in natural host-plants than in cane stalks, and the fecundity of feral moths natural hosts appeared to be higher than that of moths from sugarcane. The insect appears to have invaded sugarcane when stalk nitrogen levels reached sufficiently high levels for its survival as a result of intensive cultivation.

Temephos resistance in savanna cytospecies of Simulium damnosum Theobald s.l. and the forest cytospecies S. sanctipauli Vajime & Dunbar, from West Africa is correlated with an increase in general esterase activity. Metabolism studies indicated that esterase products were the major metabolities in both forest and savanna resistant strains of S. damnosum s.l. compared to the susceptibles. In the presence of an esterase synergist, a large amount of the oxon analogue of temephos was produced by the resistant forest cytospecies S. sanctipauli. This strain is also resistant to chlorphoxim, and it is likely that the increase in oxidative activity observed is connected with the chlorphoxim rather than the temephos resistance. There was no evidence of glutathione transferase-, oxidase- or acetylcholinesterase-based temephos resistance machanisms in the savanna species of S. damnosum s.l.

The taro-feeding delphacid genus Tarophagus is revised. Three species are recognized: T. colocasiae (Matsumura) stat. rev. & comb. n. with which T. proserpina taiwanensis Wilson is synonymized; T. persephone (Kirkaldy) with which T. proserpinoides (Muir) and T. proserpina australis Fennah are synonymized; and T. prosperpina (Kirkaldy). The three species are separated by characters of the male and female genitalia, and each has a different distribution in Asia and the Pacific. Only in Papua New Guinea are all three species sympatric. Earlier studies on biology and pest status are reviewed in the light of these investigations.

A strain of Aedes aegypti (L.) was collected in Rio Piedras, Puerto Rico, in 1987 and reared through to the F2 generation. The strain was shown to be heterozygous for resistance to a range of pyrethroids, but there was no evidence of organophosphate and carbamate resistance. Biochemical studies indicated that the pyrethroid resistance was not metabolically based. Electrophysiological studies at the neuromuscular junction of resistant insects indicated that a kdr (nerve insensitivity) type mechanism was operating in this strain. It is not known whether this mechanism was selected by earlier DDT exposure or by the recent ultra-low-volume applications of pyrethroids.

Rastrococcus invadens Williams was first noticed in Togo in 1981 and has since become a serious pest on many plants, especially mango and citrus. In June 1986, a programme for its biological control was begun, resulting in the introduction into Togo in October 1987 of an encyrtid parasitoid, Gyranusoidea tebygi Noyes. The parasitoid was reared under a simple system and releases were made from November 1987. The parasitoid established readily under a range of ecological conditions and produced significant control within the first year up to 100 km from each release point.

A commercial trial of different strategies for suppressing damage by Cryptophlebia leucotreta (Meyrick) to citrus was made in the Transvaal lowveld, South Africa. Different regimes tested were applications of the chitin synthesis inhibitor teflubenzuron at 60 mg a.i./litre and ca 30 litres/tree, inundative releases of the egg parasitoid Trichogrammatoidea cryptophlebiae Nagaraja, and a combination of the two. One objective was to examine whether application of the insecticide earlier in the season than usually recommended would enhance the subsequent impact of parasitoids, native or released. It was found that parasitoid releases throughout the season (1.3 million/ha in total) produced the best overall reduction in damage by C. leucotreta. This was due largely to their better performance than that of any other strategy early in the season. Their impact in the later part of the season was not significantly different from that of release programmes which had begun at a later stage (0·6 million/ha). Very early applications of the teflubenzuron had no apparent impact on crop losses and did not enhance the impact of subsequent parasitoid releases to a significant degree. Teflubenzuron application at a recommended time later in the season was the most successful short-term approach, but its overall impact on crop loss was diminished by damage during the unprotected period before its application. A more appropriate management programme against C. leucotreta might therefore be to combine inundative releases of parasitoids early in the season with later applications of teflubenzuron if economic thresholds show they are required. The two approaches should not be concurrent since parasitoid activity was suppressed by the chitin synthesis inhibitor.

The taxonomy of species in the braconid subfamily Microgastrinae that parasitize the larvae of Diatraea in the New World is reviewed and a brief diagnosis of each species provided. Apanteles fredi sp. n. is described from Guatemala and its relationships discussed. Information on the distribution, host associations and range in variation of species is provided, along with a revised and illustrated key to facilitate their identification.

Pieces of netting and sheeting of various types were impregnated by dipping them in permethrin emulsion. Bioassays were performed in which three species of mosquitoes were exposed to the impregnated fabrics for periods of between 15 s and 8 min. When pieces of netting and sheeting were dipped in permethrin emulsion at ambient temperature, the amount of insecticide absorbed was generally proportional to the weight of liquid taken up, i.e. there was no evidence of selective absorption. Diffusion of permethrin did not occur between pieces of netting and sheeting sewn together. The LD50 on cotton nets was found to be about three times as great as on nylon nets. Aedes aegypti (L.) was found to be more susceptible than Anopheles gambiae Giles, which was more susceptible than Culex quinquefasciatus Say. Although for most other groups of insecticides variation in time and dose have equivalent effects, for permethrin on netting this was not found to be true, i.e. on having the exposure time the LD50 was less than doubled.

Helicoverpa armigera (Hübner) and H. punctigera (Wallengren) are major pests of cotton and other field crops in Australia. Using data on then abundance of males in pheromone traps at many sites over three seasons, the spatial and temporal variation in trap catch of both species were examined using Taylor's power law and spatial autocorrelation. The distribution of both species was highly clumped, both temporally and spatially. Regression Coefficients for the relationship of spatial mean to variance (bs) were similar to those for noctuids in general, while similarly derived temporal values (bt) for H. armigera fell towards the upper end of the noctuid range and those for H. punctigera well above the range given by Taylor & Woiwood (1980). Taylor and colleagues suggested that patterns of dispersion are species-specific and that they reflect density-dependent patterns of movement towards and away from centres of abundance. Although the relationship between variance and mean abundance for both spatial and temporal aspects of trap catches of Helicoverpa is well fitted by Taylor's power law, it is argued that these patterns of dispersion are a consequence of demographic and environmental stochasticity. Little need is to invoke specific density-dependent behaviours as the major factor responsible in this case. In addition, while Taylor's power law indicated both species had a similar clumped distribution, limited autocorrelation analysis suggested a random dispersion of pheromone-trap catches for H. armigera and small scale patchiness (over distances of 1–2 km) in trap catches of H. punctigera.

Landing site preferences of fed males of Glossina morsitans morsitans Westwood were measured in ca 50-cm-wide arenas in the laboratory. Flies were presented with simple black shapes of 225 cm2 against a white back-ground. Preference ran in the order: circle < square < triangle (whether the targets were black shapes on white or white on black). However, the triangle on its side (i.e. rotated through 90°) or the square presented as a diamond (i. e. rotated 45°) were both greatly preferred over their original orientations, whereas inverting the triangle (by rotating it 180°) greatly decreased its attractiveness. These preferences were retained whether the targets were compared paired or singly. The most obvious correlation was between preference and the relative lack of horizontal features in the target. When the diamond (the most attractive target) was split horizontally by a narrow white band, its attractiveness was reduced by ca 60%, whereas when split by a vertical band the attractiveness was reduced by only ca 25%. Similarly, when an additional narrow black bar was placed horizontally beneath the diamond its attractiveness was cut by 47%, whereas when the bar was placed vertically beside it the attractiveness was cut by only 28%. These reductions occurred even though the targets should have been more attractive because of their greater edge length and area. When the effect was tested with a series of rectangles, the greater the ratio of the vertical:horizontal edge length, the greater the attractiveness. The relative inhibition of landing by the presence of horizontal features in a laboratory-tested landing site thus seems clear, notwithstanding that horizontal resting sites in nature are the most preferred.

DDT metabolism in Phlebotomus papatasi (Scopoli) was investigated and compared to that in DDT-resistant and susceptible strains of Culex quinquefasciatus Say and Anopheles gambiae Giles with the objective of establishing baselines for sandfly studies. P. papatasi produced eight metabolites of DDT, with DDE predominating, as in the two mosquito species. Both oxidases and glutathione transferases were found to be involved in DDT metabolism in insecticide-susceptible adults of P. papatasi. The activity level of glutathione transferases and the reduced and oxidized difference spectra of cytochrome P-450 were measured spectrophotometrically. The level of glutathione transferase activity in P. papatasi was lower than that in susceptible C. quinquefasciatus adults when expressed in terms of the activity per milligram of soluble protein but, in contrast, the cytochrome P-450 was slightly higher in both the reduced and oxidized states.

The feeding responses, growth and population development of Nilaparvata lugens (Stål) are quantified on a range of twelve susceptible or resistant host-plants. Paris of rice varieties carrying the Bph1, bph2 and Bph3 resistance genes are compared as hosts for N. lugens, and it is concluded that such notations do not adequately describe the diversity of plant resistance mechanisms. Evidence is presented for resistance mechanisms involving enhanced insect activity and gustatory responses to unacceptable phloem.