Visual and olfactory responses of Glossina fuscipes fuscipes Newstead to the monitor lizard, Varanus niloticus niloticus Laurenti were studied using various catching devices near Lake Victoria, Kenya. Electric nets baited with visible lizards caught more males (×2.1) and significantly more females (×2.0) than unbaited nets. Lizards concealed in electrified black PVC pipe models, simulating the shape and size of a monitor lizard, increased significantly the catches of tsetse by 2.1 times. Fresh lizard urine dispensed at an evaporation rate of 500 to 1000 mg/h also increased significantly the catches of flies at biconical traps, electrified models and electric nets. Identification of chemical constituents of the odour could improve monitoring and control strategies for G. f. fuscipes, and possibly for other palpalis tsetse species.

Host-feeding by parasitoid wasps has been viewed as a positive attribute for biological control, because hosts are killed as a result of host-feeding in addition to parasitism. Host acceptance and host-feeding responses o unparasitized vs. conspecifically parasitized hosts by the parasitoid wasp Itoplectis naranyae Ashmead were studied in the laboratory. Female I. naranyae selected to oviposit in unparasitized hosts and those that had been parasitized I h previously, in equal proportions, even when allowed access to both types of host. Females also fed upon both types of host equally. Females, however, avoided ovipositing in hosts parasitized 40 h and 70 h previously, and preferentially fed upon them when allowed access both to parasitized and to unparasitized hosts. Parasitoid progeny in hosts which had been used for host-feeding suffered a high degree of mortality. Females used host internal changes as cues for deciding whether to feed on hosts. It is suggested that immature parasitoid mortality can be increased due to female preference for using parasitized hosts for host-feeding. Hence, host-feeding by I. naranyae may not be an advantageous biological control characteristic. The adaptive significance of selective host-feeding is also discussed.

The pear thrips Taeniothrips inconsequens (Uzel) was sampled for four years in a small sugar maple Acer saccharum plantation in Centre County, Pennsylvania, USA. The life cycle of T. inconsequens was univoltine with the main period of emergence and flight from late March to mid May. Adults, eggs, and first and second instar larvae were associated with sugar maple budburst and early leaf development from late April to late May. Larval drop occurred from mid to late May. Mature second instar larvae, propupae, pupae and adults spent from June to March in the ground; development from larva to adult occurred between September and November. From March to May most (usually >90%) thrips adults and larvae sampled were T. inconsequens. No T. inconsequens males were found. In soil samples taken in spring, summer and autumn T. inconsequens were found to a depth of 50 cm but over 87% were in the top 20 cm. Almost no T. inconsequens were found in the litter layer. Large variations in T. inconsequens adult emergence and larval drop were recorded. The most important contributing factors in fluctuations of T. inconsequens populations were the length of sugar maple budburst, the degree of synchrony between thrips emergence and sugar maple budburst, and the occurence of sugar maple flowering.

A strain of Cryptolestes ferrugineus (Stephens) bred for malathion-specific resistance was found to be 650 fold resistant at LD50 when compared with a susceptible strain bred from the same stock. Resistance was more than 98% synergized by triphenyl phosphate and S,S,S-tributyl phosphorotrithioate, but unaffected by piperonyl butoxide. AChE inhibition by malaoxon varied slightly between the strains. Non-specific esterase activity as measured by the hydrolysis of α-naphthyl acetate was slightly reduced in the resistant strain whereas there were no inter-strain differences in the hydrolysis of β-naphthyl acetate. Products of in vitro metabolism of malathion were identified by thin-layer chromatography and gas chromatography-mass spectrometry as α- and β-malathion mono-acids. It was therefore concluded that resistance was due to the hydrolytic breakdown of malathion by a malathion-specific carboxylesterase. The rate of in vitro malathion hydrolysis was found to be 31 times greater in the resistant strain. In vitro inhibition studies indicated that resistance is attributable to a carboxylesterase unique to the resistant strain. The implications of these results are discussed in relation to work recently carried out on malathion-specific resistance in dipterous species.

In order to evaluate the relationships between attacks by the mahogany shoot borer Hypsipyla grandella (Zeller) and host growth and phenology, field trials of Spanish cedar Cedrela odorata and American mahogany Swietenia macrophylla established in Costa Rica were assessed intensively over an 84 week period. Height growth of C. odorata was approximately twice that of S. macrophylla, with mean growth rates of 2.0 and 1.3 cm week−1 respectively. Cedrela odorata displayed pronounced temporal variation in leaf phenology, with a minimum of 51% of trees in leaf during a relatively dry period. In contrast, the minimum proportion of foliated S. macrophylla trees was 87%. No shoot borer attacks were recorded on S. macrophylla until week 50 after the onset of assessments, whereas initial attacks of C. odorata were recorded during week 6. By week 84, the proportion of trees attacked was 74% and 77%, respectively. In both species, attacks were concentrated in seasonal peaks, coinciding with the production of new shoots. Pronounced spatial variation in attack was observed in both species. At week 12, the number of attacks per block in C. odorata was negatively correlated with available calcium concentration (r=0.85, P<0.001), whereas mean height growth of C. odorata was positively correlated with available phosphate concentration (r=0.84; P<0.0001). Significant variation in height to first damaging attack was observed in both species. By the end of the observational period, only 6% of C. odorata and 0.4% S. macrophylla remained undamaged to a height of 3 m. It is suggested that control methods for the mahogany shoot borer should take account of temporal dynamics in attack, and relationship to host phenology. Manipulation of the soil nutrient status may also form part of an integrated approach to pest management.

At least 62 species of ants were caught at baits in Philippine rice fields, notably in the bunds (levées) of irrigated rice. Many were relatively uncommon or localized. Apart from the ubiquitous Tapinoma sp. nr indicum Forel the most widespread was the aggressive Solenopsis geminata (Fabricius) which was often very abundant in fields with bunds that were disturbed by regular repair. This ant was scarce or absent in relatively undisturbed well-vegetated bunds where Pheidole spp. were sometimes common and where up to 14 different species were recorded in bunds of a single field. Colonies were spaced out along the bunds where foraging territories sometimes overlapped, except for those of the competing dominants S. geminata and Pheidole spp. In general, S. geminata retained its overall foraging areas from year to year but those of non-dominant ant species could vary considerably. Bunds of low-lying fields that are deeply flooded in the wet season were recolonized by S. geminata in the wet season. This ant occurred as separate colonies with workers from nests that differed in degree of mutual aggression. Such aggression was not observed in foraging areas. Solenopsis geminata and other species foraged into, and nested within, dry fallowed fields after the crop was harvested. In the crop season, they foraged across mud during periods of up to one week when farmers allow irrigated rice fields to drain before flooding. Solenopsis geminata workers also foraged across the closed crop canopy. At such times they were commonly observed preying on hemipteran and lepidopteran pests and on eggs and young golden snails (Pomacea canaliculata Lamarck) which are serious rice pests in the Philippines.

Flight ability of Ostrinia furnacalis Guenée was evaluated using a flight-mill in laboratory. Females flew most actively at 20–23°C, whereas the majority of the moths tested did not fly at 14–17°C. Temperature above 26°C inhibited their flight activity and survival. The age-specific flight ability of unmated males and females was similar from one to 12 days after emergence; it was highest at one day and then declined gradually. Females showed a pre-oviposition period of three to four days after emergence during which they were capable of longer continuous flight. There was no significant difference between the unmated and mated females in any aspect of flight ability at four days (commencement of oviposition) or at eight days old (peak of oviposition). In males, the flight ability of mated adults was reduced compared with that of unmated adults at both four and eight days old. Increased flight experience did not delay oviposition by mated females, but significantly reduced egg production. There was a significant negative correlation between flight duration and subsequent egg production. Ostrinia furnacalis is concluded to be an active flier that is able to male long-distance flights, because both mated and unmated adults displayed high flight ability for several days after emergence.

The performance of the egg parasitoid Uscana lariophaga Steffan was studied when reared on eggs of the bruchid storage pest, Callosobruchus maculatus (Fabricius) developing in seeds of cowpea, chickpea and pigeonpea. The beetle laid more and larger eggs on pigeonpea than on cowpea and chickpea, indicating that there was not a trade-off between number and size of the eggs. The bruchid larvae reared on pigeonpea exhibited a longer development time and a higher mortality than those reared on cowpea and chickpea. The resulting males weighed less than those reared on cowpea and chickpea. The trichogrammatid U. lariophaga parasitized more eggs when C. maculatus was reared on chickpea than when reared on the other hosts. Parasitoid larvae developed slowest and had the highest mortality in eggs of C. maculatus reared on pigeonpea compared to those reared on cowpea and chickpea; the sex ratio (% of females) of the resulting adults was also higher. The high mortality and long development time of C. maculatus reared on pigeonpea indicated that this legume was less favourable to C. maculatus than chickpea or cowpea. This was probably also true for the parasitoid since the mortality was higher and development longer in eggs of C. maculatus reared on pigeonpea compared to those reared on cowpea and chickpea. Therefore, when host eggs were larger and of lower nutritional quality, the proportion of female egg parasitoids was greater.

Pidorus euchromioides Walker has two separate diapauses during its life cycle, a winter diapause as a fourth larval instar and a summer diapause as a prepupa in a cocoon. Winter diapause was induced by short photoperiods. The critical day length of 13 h 20 min to 13 h 40 min at 23.3°C under insectary conditions was very similar to the critical day length (13 h 32 min) observed in the field. Sensitivity to day length was restricted to the first 9 days, corresponding to the first and second instars. The duration of larval diapause was not only strongly correlated with the inducing photoperiod, but also dependent on the number of short days experienced during the larval growth period. The shortest diapause occurred at the critical day length, or when the larvae were exposed for 6 days (a critical number of short days) to a photoperiod of LD 12 h:12 h. The summer diapause appeared to be primarily determined by a genetic factor and only occurred in part of the overwintering generation and the first generation. The two different diapause mechanisms play important roles. Winter diapause ensures that P. euchromioides synchronizes its development and activity with the phenology of specific host plants, and summer diapause provides the species with a high degree of adaptation to an unpredictable environment.

Bacillus thuringiensis Berliner isolates were detected in 57% of 801 samples of rice grain dust, soil, rice field arthropods, and miscellaneous habitats (rice straw compost and mammal faeces) collected at 100 sites in the Philippines. The collection yielded 3950 isolates of B. thuringiensis (8.7 isolates/positive sample). Grain dust from rice mills was the richest source (63% of the samples were positive, with 10.2 isolates/positive sample), followed by rice field arthropods, soil, and miscellaneous habitats. Polyclonal antibodies to six δ-endotoxin groups (Cry1A, Cry1B, Cry1C, Cry1D, Cry1E, and Cry3A) were used in enzyme-linked immunosorbent assays (ELISA) to characterize the toxins produced by each isolate. Subsamples of isolates representing the diversity of isolate sources and δ-endotoxin profiles were bioassayed against the yellow stem borer, Scirpophaga incertulas (Walker) and striped stem borer, Chilo suppressalis (Walker). Eighteen isolates highly toxic to both species were selected for characterization of δ-endotoxin genes by polymerase chain reaction (PCR) with primers specific to 14 genes or gene subfamilies, and Western blotting with Cry2A antibodies. At least two novel δ-endotoxin genes, related to cry1B and cry1F, were detected by DNA sequencing of PCR products.

The Australian cotton industry relies almost exclusively on synthetic insecticides for control of early season pests. These insecticides often disrupt predatory insect activity in the field. Potential predators of the twospotted spider mite, Tetranychus urticae Koch, in cotton, identified in field and confirmed in laboratory experiments, included a theridiid spider, a phytoseiid mite, a lacewing larva, predatory thrips, several Coccinellidae and several Hemiptera. These predators were mostly generalists, having previously been reported as predators of aphids or caterpillars of Helicoverpa spp. The effect of insecticides on T. urticae and its predators was evaluated in three field experiments. Cotton was artificially infested with T. urticae then sprayed five times at seven to ten day intervals with either dimethoate (140 g ai/ha), thiodicarb (750 g ai/ha and 187.5 g ai/ha), endosulfan (735 g ai/ha and 367.5 g ai/ha), methomyl (169 g ai/ha) or amitraz (400 g ai/ha). Tetranychus urticae populations reached higher densities in dimethoate, thiodicarb and methomyl treated cotton than in untreated cotton. Population densities of T. urticae in cotton treated with low rates of endosulfan or thiodicarb were similar to controls, while those in cotton treated with amitraz were lower. All insecticides caused significant reductions in at least one predator group. Significant negative relationships were found between early season abundance of predators and the mid-season abundance of T. urticae and positive relationships between predators and the lag-period for T. urticae outbreaks to develop. Predation is implicated as a key factor influencing the early season survival of T. urticae. The implications for developing integrated pest management strategies in cotton are discussed.

Whiteflies of the Bemisia tabaci (Gennadius) group are a major and increasing problem for agriculture throughout the world. In particular, the appearance and rapid spread of a highly virulent new form (silver-leaf whitefly, or B-biotype; Brown et ah, 1995), and recognition that the problem involves a complex of sibling species, host races and/or biotypes has stimulated intensive multidisciplinary research on this insect in recent years (Gerling & Mayer, 1996).