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.

A simple optical method for automatic recording and classification of a suction trap catch is described. The insects are illuminated against a dark background as they pass through a detection volume, and the amount of scattered light is used to measure insect size. The design centres on the detection volume, which is a volume through which the insects are made to pass, and within which they may be detected. The design is approached in four stages: 1. Delivery of insects to the detection volume. 2. Illumination of the detection volume. 3. Collection and detection of scattered light. 4. Signal analysis. The analysis could also be applied to related techniques. Results with a prototype demonstrate that classification into broad size categories is straight-forward (e.g. approximately three classes spanning body lengths of 2–7 mm), despite uncertainties of insect reflectivity, aspect and trajectory. Applications of the method are discussed, along with a brief mention of alternative techniques.

The reproductive condition and mating status of female Helicoverpa armigera (Hübner), H. punctigera (Wallengren) and the mating status of the armywormMythimna convecta (Walker), trapped in tower-mounted light traps were studied over a four and a half year period, from November 1985 to December 1989. The traps were mounted on towers (40 and 50 m high) in two geographically distinct sites, one located at Point Lookout and the other at Mt Dowe both in north-eastern New South Wales, Australia. At the Point Lookout site, 132 females of H. armigera and 366 of H. punctigera were examined and of those, 88.7% and 89.9% were unmated and immature, respectively. Most of the remaining females of both species were mature and mated. Of the matedH. armigerafemales, 78.6% carried only a single spermatophore, the remainder having either two or three spermatophores. Most of the matedH. punctigerafemales (97.1%) carried only a single spermatophore and the remainder had no more than two. Females ofM. convectawere predominantly (97.1%) unmated. At the Mt Dowe siteH. punctigeraadults were predominant and all 44 females of this species examined were unmated and non-gravid. Pre-reproductive flight byHelicoverpaspp. andM. convectais considered as an important component of the life-history strategies of these insects. Flexibility in the timing and spacing of reproductive effort is seen as enabling colonization of heterogeneous environments.

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 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.

Biological characteristics of the poinsettia strain of Bemisia tabaci Gennadius were investigated on poinsettia by laboratory experiments at five temperatures (range: 16°C–28°C). In addition, the effect of rearing B. tabaci on the two plant species, Nicotiana tabacum (tobacco) (Solanaceae) and Euphorbia pulcherrima (Euphorbiaceae) (poinsettia) was investigated. The temperature-dependencies were established for the developmental time for eggs and egg-to-adult phase, juvenile mortality, adult female life-span, pre-oviposition period, age-specific fecundity, and sex-ratio. The lower temperature thresholds for egg-development, development from egg to adult and for ovipositional adults were estimated as well as the lower temperature threshold for oviposition. The thresholds were 12°C, 14°C, 8°C and 14°C, respectively. Egg-development required 126 day-degrees and the entire development into adults 327 day-degrees. Mortality was highest at 16°C, being 19.3% in the egg-stage and 95% from egg to adult. The pre-oviposition period and the adult life-span were 40 and 360 day-degrees. The age-specific fecundity of B. tabaci was described by a temperature-dependent model. The maximum daily fecundity rate was attained after 60 and 125 day-degrees for B. tabaci reared on tobacco and poinsettia, respectively. The fecundity was highest for B. tabaci reared on poinsettia. The sex-ratio was in favour of females at and above 19°C and increased with temperature. Estimates of the net reproductive rate, the intrinsic rate of increase, the finite rate of increase, the mean generation time and the doubling time were obtained. A positive linear relationship was found between rm and temperature, the values ranging from 0.0012 at 16°C to 0.1263 at 28°C.

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.

The effect of ivermectin treatment of cattle on the rate of dung beetle colonization of cow pats was assessed by pitfall trapping in Denmark, Tanzania and Zimbabwe. Ivermectin was injected subcutaneously into heifers at the recommended dose of 0.2 mg/kg body weight, and dung to be used as bait in pitfalls was collected at intervals after treatment. In one experiment in Denmark, species of the scarab beetle Aphodius and the hydrophilids Sphaeridium and Cercyon, preferred control dung from untreated cattle; no preference was found in two other experiments, involving some of the same species. In the Tanzanian trials, the overall tendency for scarabaeid beetles was to prefer control dung. In Zimbabwe, two scarabaeid species (Euoniticellus intermedius (Reiche) and Liatongus militaris (Castelnau), both belonging to Oniticellini) were particularly attracted to dung from treated cattle; two other scarabaeids showed no preference. It is concluded: 1. That ivermectin therapy can affect the rate of dung colonization by attracting or repelling beetles. 2. That the responses are probably not caused by ivermectin per se, but by some side effect, the nature of which is obscure and unpredictable with our present knowledge.

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.

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.

Daily light trap catches of Scotinophara coarctata (Thunberg) were analysed from mid-September 1986 to December 1990 and the physiological status of the trapped adults was examined. The catch size fluctuated synchronously with the lunar phase; large catches occurred around the full moon period and very few adults were trapped around the new moon period. Seasonally, the catches were large from January to March and from July to September, while they were small from May to June and October to November. The seasonal fluctuations of the catches seemed to be related to the growth stages of the rice plants on which the adults multiplied. The sex ratio of trapped adults was biased toward males, unlike that of the cage-reared insects which was 1:1. Most of the trapped females showed undeveloped ovaries and some of these females appeared to have oviposited previously. Light-attracted adults showed a considerable tolerance to starvation and survived for 20–30 days when they were given water, but for only two days in the absence of water. When the light-attracted females were supplied with food, their ovaries developed rapidly and females with mature eggs were produced after nine days. When the starvation period was prolonged, the ovaries remained immature and the fat bodies reduced in size. The nocturnal take-off of the adults was not triggered simply by the full moon illumination. Adult eclosion did not synchronize with the moon cycle.

Extracts of the leaves of the New Zealand native tree Pseudowintera colorata (Raoul) showed insecticidal and antifeedant activity against the webbing clothes moth, Tineola bisselliella (Hummel), and antifeedant activity against the Australian carpet beetle, Anthrenocerus australis (Hope). Assay-directed fractionation showed that two sesquiterpene dialdehydes, polygodial and 9-deoxymuzigadial, were responsible for these activities. Both compounds had similar antifeedant and insecticidal activity at rates from 3 to 0.4 mg/g wool in bioassays.

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.

Fourth instar larvae of a new strain of Culex quinquefasciatus Say from Tanzania (TANGA) were tested for insecticide resistance. Initially, the resistance ratio (RR) to chlorpyrifos was 41.8, to temephos 30.8, to propoxur 3.7. After 2–3 years of laboratory culture, resistance to chlorpyrifos and propoxur had declined (chlorpyrifos 5.7, 3.8; propoxur 1.9, permethrin 1.9). Significant synergism was found between s, s, s-tributyl trithiophosphate (DEF) and chlorphyrifos, reducing the RR from 8.0 to 2.5. Synergism between piperonyl butoxide and permethrin was less than in a susceptible control strain. Twelve esterase isozymes of different relative mobilities (Rm) on polyacrylamide gel electrophoresis were identified, ten of which remained when the strain was reinvestigated two years (approximately 32 generations) later. Null activity for all but one of these bands was observed in some larvae. Four esterase bands (Rm 0.25, 0.27, 0.31, 0.34, designated A2, A3, B2, B3) showed polymorphism in activity, with very intense bands in some larvae. The mean frequency of bands with activity greater than standard, declined as organophosphorus (OP) resistance declined, but resistance was unconnected with the frequency of nulls at these positions. In mass larval assays of in vitro sensitivity of acetylcholinesterase (AChE) to propoxur, the I50 exceeded 10x10−4M, compared with 0.1x10−4M in a reverted resistant strain (RANGOON). Single larvel assays revealed heterogeneity, which was interpreted on the basis of an AChE resistance allele (AceR) with a frequency of 0.23.

A laboratory bioassay was developed to allow blind testing of panels of odours for their effect on target-orientated behaviour of tsetse (Glossina spp.) in the laboratory. Landing responses of G. m. morsitans Westwood on black and blue targets were increased up to four-fold in the presence of carbon dioxide, but no significant effect of any other odours could be demonstrated. 2-methoxy phenol gave an apparent increase in landing behaviour in the laboratory, but this substance diminished rather than increased landing of G. pallidipes Austen and G. m. morsitans on targets in the field, as well as repelling tsetse from the target vicinity. Black, blue and red targets elicited strong landing behaviour in male G. m. morsitans in the laboratory, and white and yellow targets elicited little or none, whether carbon dioxide was present or not. In the field, high ultraviolet reflectivity increased landing behaviour of G. pallidipes, but only when there was a proportion of transmitted light through the target. Ultraviolet reflectivity always reduced overall attraction of tsetse to a single-coloured target. Two-coloured targets incorporating ultraviolet-reflecting white cloth obtained strong landing on the white panels, but caught fewer flies overall than all-black, or blue-and-black targets.

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.

Light traps were operated between September and April for five years on towers on mountain tops at two locations in northern New South Wales, Australia. The traps were designed so that their lights could only be seen from above, and therefore only insects engaged in high altitude flight, presumed to be migrants, were captured. The catch consisted mostly of Noctuidae and Sphingidae. Sweep netting failed to reveal local breeding, and for many species there were few host plants close to the traps. A total of 51,580 moths were trapped at Point Lookout and 10,223 at Mt Dowe. Sphingids, mostly Hippotion scrofa (Boisduval), comprised 26.9% of the catch at Point Lookout, but only 2.6% at Mt Dowe, and there were more species of noctuids at Point Lookout (44) than at Mt Dowe (15). The most common noctuid species were Agrotis infusa (Boisduval), Mythimna convecta (Walker), Helicoverpa punctigera (Wallengren), H. armigera (Hübner), Dasygaster nephelistis Hampson and A. munda Walker. Known or suspected migrants comprised 94.6% of the catch at Point Lookout and 99.9% at Mt Dowe. However, there were at least 24 species not previously suspected as migrants. The seasonal distribution of catches varied between sites and years. Some species showed peaks in both spring and autumn in some years, but only in spring in other years. Many of the less common species were caught only in summer and autumn. Large catches were usually obtained overs short periods (1–2 nights), separated by long periods when catches were very low. These large catches, which were thought to represent major migrations, accounted for 76% of the catch in 3% of the trapping period at Point Lookout, and 87% of the catch in 2% of the trapping period at Mt Dowe.

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.

Evidence from observing resistance in decline in fourth instar larvae of the multiple resistant MUHEZA strain of Culex quinquefasciatus Say from Tanzania (MUHEZA), showed that the major mechanisms for chlorpyrifos and propoxur resistance were different. Resistance to chlorpyrifos declined more than 400-fold (from an initial resistance ratio (RR) of 14285) while resistance to propoxur remained stable for at least 30 generations of laboratory culture. Significant synergism was found between propoxur and piperonyl butoxide (PB), propoxur and s,s,s-tributyl trithiophosphate (DEF), and permethrin and PB, but antagonism occurred between chlorpyrifos and PB, and no synergism between chlorpyrifos and DEF. Nine esterase isozymes active against naphthyl acetates on polyacrylamide gel electrophoresis (PAGE), were identified, four (A2, A3, B2, B3) showing polymorphism in activity, with very intense expression at one or other position in more than 32% of larvae, and null expression in less than 30%. The frequency of intense bands and of nulls both declined as resistance declined. A selected substrain (MUHEZA-fb), breeding true for A2, A3, B2 and B3 at the standard level of activity, showed almost stable chlorpyrifos resistance (RR=1428–1785) for approximately 35 generations. In mass larval assays of in vitro sensitivity of acetylcholinesterase (AChE) to propoxur, the I50 in MUHEZA was 950-fold greater than in a reverted resistant strain (RANGOON). Single larval assays indicated an AChE resistance allele (AceR) at frequency 0.43. PAGE of AChE revealed nine isozymes in MUHEZA and five in RANGOON, three of which were in common. It is concluded that propoxur resistance was due principally to AceR with a minor influence from oxidases and non-specific esterases, while chlorpyrifos resistance was due to an interaction between AceR and non-specific esterases, the latter exerting the dominant effect.