Many aphid species have life cycles which alternate between asexual reproduction during spring and summer and sexual reproduction in autumn. This paper describes the sequences of morphs produced by clones of Rhopalosiphum padi (Linnaeus) in response to a range of photoperiods and temperatures in the laboratory, and under semi-natural conditions at the time of year when the transition from parthenogenetic to sexual reproduction occurs. By using similarities in the order in which the various morphs were born, clones of R. padi were found to produce eight progeny sequence types. A clone of R. padi will produce these sequence types sequentially as it changes from parthenogenetic to fully sexual reproduction. The progeny sequence produced by clones under conditions corresponding to those of spring and summer consist of parthenogenetic females only. During late summer, production of parthenogenetic females is followed by males. Later in the year, a clone produces progeny sequences consisting of parthenogenetic females, gynoparae and males. The asexual phase of reproduction is terminated in late autumn when only gynoparae and males are born. A minority of clones terminate parthenogenetic reproduction by producing only gynoparae. The function of these changes in progeny sequence in maximizing the reproductive success of a clone of R. padi is discussed.

The parasitoids Microctonus hyperodae Loan and M. aethiopoides Loan have been introduced into New Zealand to control the forage pests Listronotus bonariensis (Kuschel) and Sitona discoideus Gyllenhal, respectively. Laboratory experiments were carried out to investigate the effect of host–parasitoid ratio, and exposure time on host survival, parasitism, oviposition and feeding. Cages of 20 field collected weevils were exposed to 0, 1, 3 or 6 parasitoids for 0, 1, 12 or 48 hours, maintained until parasitoid pupal emergence, and surviving weevils dissected. Over the ranges studied, increasing parasite number, and to a greater extent, period of exposure of parasitoids to their hosts increased parasitism levels. Microctonus aethiopoides achieved higher levels of parasitism in S. discoideus at the lower parasitoid contact treatments than did M. hyperodae in L. bonariensis. Fecundity in unparasitized weevils was progressively reduced in both L. bonariensis and S. discoideus in relation to increasing exposure to parasitoids. Feeding was reduced by about 40% in L. bonariensis for at least four days after parasitoids were removed, and in S. discoideus for the duration of the experiment, averaging 15%. Results were discussed in relation to possible mechanisms of indirect effects of parasitoids on unparasitized hosts.

Adults from seven strains of Bemisia tabaci (Gennadius) were tested with nine insecticides or combinations in both leaf-dip bioassays and the Rothamsted field simulators. A statistical model was used to describe the survival of the insects in the field simulators and comparisons made to the resistance factors from leaf-dip assays. Strains of B. tabaci shown to be susceptible in bioassays were well controlled by field rates of the insecticides in the field simulators. For each insecticide or combination, the degree of adult survival in field simulators after insecticide treatment was positively related to the resistance factor. However, similar resistance factors for different insecticides gave quite different adult field simulator survival. In populations with high resistance factors, adult mortality in the field simulators after insecticide application was not different to untreated controls. These data provide information about the implications of B. tabaci resistance on the field performance of insecticides.

The insect growth regulator buprofezin was tested using a leaf-dip assay on immatures of Bemisia tabaci (Gennadius). The method was robust and repeatable, and baseline data were calculated for a laboratory strain and a number of field collections from Pakistan where the insecticide has not been used. A baseline LC50 of 0.53 ppm buprofezin was defined and compared to other field collections. Populations known or suspected to have been intensively selected with buprofezin showed substantial tolerance to the insecticide at both the LC50 and at specific diagnostic doses, with the highest resistance factor of 47 fold in a population from the Netherlands. Reasons for the variation between populations, biotypes and geographical areas are discussed and the dangers of human-assisted movement of resistance genes are highlighted.

The ovipositional behaviour of the mirid predator Macrolophus caliginosus Wagner, a potential biological control agent of glasshouse pests, was studied in detail using a modified video camera technique. In the laboratory, females laid their eggs in the leaves of tobacco plants. They remained generally motionless on the main veins of the leaves, raised their body, folded the rostrum towards the thorax and extended their ovipositor when selecting a site in which to oviposit. The ovipositor was inserted into the plant tissue by a downward and forward thrust of the body and contractions of the abdominal muscles. After a period of immobility, the ovipositor was retracted and the insect's body and organs returned to their initial positions. This behaviour was preceded and followed by extensive rostral exploration of the oviposition site. In most females the same area was explored before and after egg-laying and the ovipositor was inserted approximately in the middle of the selected area. The sequence and pattern of ovipositional behaviour varied between females.

Rainfall records for 23 years at 21 selected stations in Kenya were summarized and compared with the numbers of outbreaks of armyworm Spodoptera exempta (Walker) reported in the following season. The numbers of outbreaks were found to be negatively correlated with the rainfall of the 6–8 months preceding the start of the season. Stations in south-eastern Kenya, including the coastal belt which harbours the most extensive off-season source populations of S. exempta, were identified as key stations for forecasting whether to anticipate local or countrywide armyworm outbreaks next season. A scheme is suggested that would enable a provisional forecast to be made as soon as the long rains (April–May) rainfall records were available, and confirmed or revised subsequently in the light of the June–October rainfall at stations in south-eastern Kenya.

Based on the fact that in haematophagous Diptera, the basal bodies, groups of six to nine specialized epithelial cells in the calyx wall within the ovariolar sheath, become granular after ovulation, a method for rapidly determining parity of the females has been developed. After supravitally staining intact ovaries with fresh neutral red solution in physiological saline (1:3000–1:5000) for one to three minutes, granular basal bodies in parous females can be clearly recognized under a stereo-microscope or a compound microscope with a raised condensor. The advantages of the method are its speed, accuracy and simplicity.

Observations were made on the developmental responses of the North American braconid species, Eubazus crassigaster, a parasitoid of the white pine weevil, Pissoles strobi, and three European congeneric species, E. semirugosus, E. robustus, and Eubazus sp. Several populations of Eubazus spp. were compared in their phenology in the laboratory and under natural conditions. When reared in the laboratory on non-diapausing Pissodes castaneus, mountain populations of E. semirugosus and E. robustus entered into an obligatory diapause in the host larva, whereas all the other populations tested developed continuously. Diapausing larvae continued their development only after having experienced at least three months at 2°C. Non-diapausing populations of Eubazus spp. significantly differed in the duration of pre-imaginal development, with E. semirugosus being the fastest developing species and E. robustus the slowest. Outdoor rearings of Eubazus spp. on P. castaneus showed that E. crassigaster, Eubazus sp. and the lowland biotype of E. semirugosus emerged in the year of oviposition if this occurred early enough to allow parasitoid development. In contrast, a majority of E. robustus individuals overwintered in the host larvae, regardless of the oviposition date. The diapausing, mountain biotype of E. semirugosus is considered as the most promising candidate for control of P. strobi in Canada, because it is likely to be better adapted to the life cycle of the target host than the other Eubazus spp., including the native E. crassigaster.

Outbreaks of the winter moth, Operophtera brumata Linnaeus (Lepidoptera: Geometridae), have recently become widespread on heather moorlands in northeast Scotland. These outbreaks represent remarkable phenomena given the poor nutritional quality of the dominant moorland host plant Calluna vulgaris (Linnaeus) Hull (Ericaceae). Winter moth performance on C. vulgaris was compared with that on the other available moorland host plant, Vaccinium myrtillus (Linnaeus) (Ericaceae), and parasitism levels were measured in two moorland outbreak populations. Larval densities in the field were generally higher on Calluna than on Vaccinium. However, larvae showed better survival, more rapid development and greater pupal weights on Vaccinium than on Calluna. Feeding trials indicated that Vaccinium was more digestible than Calluna. No evidence of parasitism was found in a high-altitude moorland winter moth outbreak population from mainland Scotland, but the parasitoid Phobocampe neglecta (Holmgren) (Hymenoptera: Ichneumonidae) was present in 27% of larvae from a lower-altitude moorland outbreak on Orkney. The results indicate that the presence of Vaccinium and the opportunity to escape from parasitism may facilitate O. brumata outbreak formation in high-altitude moorland sites. However, neither factor can provide a full explanation for the present phenomenon.

We investigated the resistance potential of a red-coloured Japanese strain (JR) of a tobacco feeding form of Myzus persicae (Sulzer) of the M. persicae species complex closely related to the tobacco aphid Myzus nicotianae Blackman. Bioassays were performed with a range of insecticides, imidacloprid, nicotine and cartap, thought to act on nicotinic acetylcholine receptors in vivo, as well as with two conventional insecticides, pirimicarb and oxydemeton-methyl, acting on acetylchol-inesterase (AChE). Compared to a susceptible strain, JR showed high resistance to pirimicarb and oxydemeton-methyl, but was far less resistant to nicotine, cartap and imidacloprid. Imidacloprid was, among the insecticides tested, the most active compound in contact and ingestion bioassays. Compared to the susceptible strain, JR showed four-to seven-fold resistance to imidacloprid depending on the type of bioassay. Resistance factors for other insecticides tested in an oral ingestion bioassay were: cartap five-fold, nicotine nine-fold, oxydemeton-methyl 107-fold and pirimicarb > 385-fold. JR showed high carboxylesterase activity. Polyacrylamide gel electrophoresis indicated esterase FE4 as the major carboxylesterase. As for most M. persicae strains and some Greek strains of M. nicotianae, JR was monomorphic for glutamate oxalacetate transaminase. Studies with pirimicarb showed a marked insensitivity of AChE to inhibition by this chemical, whilst such insensitivity could not be detected with the organophosphate insecticide oxydemeton-methyl. Receptor binding assays with [3H]-imidacloprid in aphid homogenates revealed I50-values of 0.4 to 0.8 nM and no statistical difference between the JR and susceptible strain.

Laboratory experiments were conducted to measure the susceptibility of larvae of the sandfly Phlebotomus papatasi Scopoli to the insect pathogen Bacillus sphaericus applied to the larval breeding medium. B. sphaericus had no effect on larvae aged 30 ± 2 days old, but larvae aged 13 ± 2 and 20 ± 2 days were highly susceptible and a clear dose response effect was detected. When B. sphaericus was left in the rearing medium for 18 days there was a significant increase in larval mortality, indicating persistence and possibly recycling. The results support the feasibility of employing B. sphaericus in the integrated control of sandflies.

Yellow starthistle (Centaurea solstitialis Linnaeus) (Compositae), native to Eurasia and the Mediterranean Basin, is a spiny and poisonous, naturalized, invasive weed of grasslands and other environments in the western USA. Chaetorellia australis Hering is a trivoltine natural enemy of yellow starthistle whose larvae feed on developing seeds within capitula. Following host-specificity studies in Greece and the USA, C. australis was first introduced from Greece into the USA in 1988 for the biological control of yellow starthistle. Field samples of yellow starthistle capitula revealed that 10.3% (four years after initial release) and 18.0% (three years after initial release) of capitula at Colfax, Washington, and Merlin, Oregon, respectively, were infested by ≥ 1 C. australis (mature larvae or empty puparia). Both sites also contained naturalized, weedy populations of, Centaurea cyanus, a second host-plant of Chaetorellia australis. The fly was also recovered from Centaurea cyanus capitula two years after its release at Kendrick, Idaho. The potential importance of the presence of C. cyanus for Chaetorellia australis and biological control of yellow starthistle is discussed. At the Colfax site, all infested yellow starthistle capitula contained 1 C. australis, while at the Merlin site 28.8% of infested capitula contained > 1 C. australis, with a mean of 1.36 C. australis per infested capitulum. A preliminary seed destruction impact study at the Merlin site showed that there was a 83.4% reduction in seeds per capitulum infested by ≥ 1 C. australis, and the presence of > 1 C. australis resulted in a 95.4% reduction in seeds per infested capitulum.

We compare the pest status and age structure of bush fly,Musca vetustissima Walker, populations, and the abundance of native dung beetles at Uriarra, ACT, for five fly seasons before (1976–81) and three seasons after (1990–93) the exotic dung beetles Euoniticellus fulvus (Goeze) and Onthophagus taurus (Schreber) became established in the area during the late 1980s. Fly populations in all post-introduction seasons of 1990–93 were much older than in the pre-introduction seasons, indicating reduced levels of local fly breeding and higher proportions of immigrants. During the pre-introduction period, the fly annoyance index exceeded the ‘minimum discomfort’ threshold of 10.0 in parts of all seasons. The mean index was 11.3, and this did not differ significantly between seasons. The total dry weight of dung beetles at the time of the first influx of bush flies each year was consistently below 3 g/dung pad which was apparently too low to depress bush fly breeding below their replacement level of 3%. The mean annoyance index of 3.1 for the 1990–91 season was significantly lower than for the pre-introduction period and the total dry weight of beetles during November-December exceeded 3 g/dung pad on all sampling occasions. In the 1991–92 and 1992–93 seasons fly annoyance indices reverted to pre-introduction levels (seasonal means of 13.7 and 7.8 respectively) and total dry weight of beetles was again below 3 g/dung pad when the bush flies first appeared. Survival of immature bush flies in local dung pads remained below the replacement level of 3% during 1990–91, but exceeded 3% on two occasions during 1991–92. Apart from 1976–77, when mean catches of native dung beetles (O. australis and O. granulatus) were exceptionally high, mean catches of native dung beetles during pre- and post-introduction years were very similar, but the mean dung beetle biomass increased following the establishment of exotic species.

The effects of the aphicide pirimicarb on the foraging behaviour of the aphid parasitoid Diaeretiella rapae were investigated in the laboratory, using aphid-infested and uninfested, young oilseed rape plants. Female parasitoids spent significantly less time foraging on plants sprayed with pirimicarb within the previous 24 h than on untreated plants, regardless of the presence of aphid hosts. Whilst foraging on sprayed plants, parasitoids spent relatively more time walking than they did when foraging on untreated plants. On sprayed plants foraging parasitoids tended to avoid leaf surfaces, thereby reducing the chances of encountering aphid hosts whilst on the plant. These sublethal effects of the aphicide on foraging parasitoids would considerably reduce their impact on aphid populations which survived in a crop after spraying. This has important implications for the control of aphids, such as Myzus persicae, which have developed pesticide resistant strains.