Life-history parameters of different biotypes of the whitefly Bemisia tabaci (Gennadius) species complex were reviewed. This included the B-biotype of B. tabaci, identified as B. argentifolii (Bellows & Perring). Comparisons were made among different biotypes on cotton, among host plants for biotype B and among the whitefly species B. tabaci and Trialeurodes vaporariorum (Westwood), the greenhouse whitefly. The biotype identification of different populations of B. tabaci was summarized in a table. Biotypes discussed were A, B, Indian and biotypes of the Old World group. Temperature dependent relationships were estimated for egg development rate, development rate from egg to adult, immature mortality, adult longevity, sex-ratio, pre-oviposition period and fecundity. The fitted curves will be used as input for a simulation model of the population dynamics of B. tabaci in a greenhouse when parasitoids are released. The model makes it possible to evaluate the integrated effect of different life-history parameters and behavioural parameters of parasitoids on whitefly population levels in a greenhouse.

The synthetic juvenile hormone analogue (S)-hydroprene can control populations of the oriental cockroach Blatta orientalis Linnaeus. Eradication of B. orientalis infestations, however, can take in excess of two years. In an attempt to reduce the time (S)-hydroprene takes to eliminate a population of oriental cockroaches, we explored the possibility of using the oothecal endoparasitoid Aprostocetus hagenowii Ratzeburg in combination with (S)-hydroprene. For such a strategy to be successful, it is important that the parasitoid remains substantially unaffected by (S)-hydroprene. When A. hagenowii was exposed to B. orientalis oothecae in the presence of (S)-hydroprene, female parasitoids showed no reduction in their capacity to attack hosts and their fecundity was not compromised. (S)-hydroprene, at dose rates of 18 mg/m2 and 100 mg/m2, induced deformity in approximately 12% and 33% respectively of parasitoids that emerged. No reduction in reproductive viability was seen in morphologically normal F1 parasitoids. Deformed F1 parasitoids, exposed to the higher (S)-hydroprene dose, showed a 71% reduction in the number of oothecae attacked and a 50% reduction in the number of offspring produced. These results indicate that A. hagenowii could be used in combination with (S)-hydroprene in an integrated pest management programme against B. orientalis.

Spectral sensitivity of the wasp Trybliographa rapae (Westwood), a parasitoid of cabbage root fly larvae, was measured by the electroretinogram (ERG) technique and by a complimentary behavioural technique, to 15 selected wavelength bands from 340 to 670 nm. Peaks of electroretinogram sensitivity were found in the ultraviolet, blue and green-yellow regions of the spectrum. This corresponds to known classes of photoreceptor present in the Hymenoptera. Behavioural peaks of phototactic attraction were found in the ultraviolet and green-yellow regions, but not in the blue. No differences were observed between the sexes. We suggest that ultraviolet and green-yellow wavelengths initiated ‘escape’ and ‘foliage’ orientated behaviour respectively. Blue wavelengths appear to have a less specific function but may be important for colour discrimination. Blue wavelengths did, however, become significantly more attractive to female wasps after a pre-experimental conditioning period involving exposure to blue wavelengths in combination with swede infested with cabbage root fly larvae. Thus T. rapae has been demonstrated to show plasticity in its visually motivated behaviour. This may prove advantageous in the development of an artificial egg collecting technique for this species.

Two new cytotypes of the onchocerciasis vector blackfly Simulium exiguum Roubaud are described from amazonian Ecuador. As transmission of the disease does not occur in the region, the two cytotypes are not currently vectors, The Napo form (N = 113) differs cytologically from the chromosomal standard of the species, the Cayapa form, through possession of the fixed paracentric inversions IL-E and IIIL-L; the Huatarac form (N = 22) differs by the fixed inversions IL-L and IIIL-D + L. Both forms form a subcomplex, termed the ‘amazonian’ subcomplex, through sharing the fixed inversion IIIL-L. They also share a number of polymorphic inversions, but neither form possesses sex-linked inversions. The fixed and sex-linked inversions of the previously described Aguarico form were found to be polymorphic and autosomal in the Napo and Huatarac forms, suggesting a close genetic relationship among these forms. The Napo form is distributed throughout the Napo river system (except in the Rio Huatarac) and found in the Rio Aguarico, whereas the Huatarac form is unique to the Rio Huatarac. As their distributions in this study were allopatric, the species status of the two cytotypes could not be tested. The Aguarico form was not found in the Rio Aguarico, nor in any of the other rivers sampled. Whether the Napo form has replaced the Aguarico form in the Rio Aguarico, or whether its absence is due to seasonal variation requires further investigation.

The fruit fly genus Ceratitis (Diptera: Tephritidae) comprises several important pest species attacking a wide range of unrelated fruits. This is the second paper in a series revising this genus, and deals with representatives of the subgenus Ceratalaspis. Thirty-six species are recognized, of which five are described as new: C. sucinisp. n., C. hancockisp. n., C. neosticticasp. n., C. paradumetisp. n. and C. mlimaensissp. n.Ceratitis pycnanthi (Ghesquière) is considered to be synonymous with C. striatella Munro, and the possible synonymies of C. giffardi Bezzi and C. sarcocephali (Bezzi) with C. cosyra (Walker), as well as C. lineata (Hering) with C. striatella Munro are discussed. Lectotypes are designated for the following species: C. connexa (Bezzi), C. discussa Munro, C. divaricata (Munro), C. dumeti Munro, C. lentigera Munro, C. lunata Munro, C. marriotti Munro, C. melanopus (Hering), C. parinarii (Hering), C. quinaria (Bezzi), C. scaevolae (Munro), and C. simi Munro. A key is provided, with illustrations of mesonotal and wing patterns and shape of aculeus tip. All species are Afrotropical and most are restricted to the sub-saharan region, except for C. quinaria which is also known from the Middle East (Yemen). Distribution and known host plant data are given. Tentative species groups within the subgenus are discussed.

A two-year pitfall trapping study was performed to test the preference of coprophilous beetles (Hydrophilidae, Scarabaeidae, Staphylinidae) for dung from untreated cattle versus dung from cattle treated topically one or four weeks previously with a recommended dose of ivermectin in a pour-on formulation. In 1994, significantly more Aphodius fimetarius (Linnaeus) and A. distinctus (O.F. Müller) at each of two sites were collected with dung from treated cattle. No differences were detected for other taxa. In 1995, significantly fewer individuals of ten taxa, including A. fimetarius and A. distinctus, were collected with dung from treated cattle. No differences were detected for other taxa. A change in cattle diet may have altered levels of faecal residues, thereby changing beetle preferences between years. Comparisons between periods of spring and autumn activity identified a change in seasonal preferences for at least some species. Similar numbers of Onthophagus nuchicornis Linnaeus and of A. fimetarius were collected in spring with dung from treated or untreated cattle, but significantly more individuals of both taxa were collected in autumn with dung from untreated cattle. In contrast, the preference of Aphodius prodromus Brahm for dung from treated cattle was unchanged between spring and autumn. These results show that ivermectin therapy does influence the colonization of dung from treated cattle. However, the nature of this influence is confounded by extraneous factors. Until such time that these factors can be accounted for, general predictions regarding the effect of ivermectin therapy on the colonization of dung by coprophilous insects are premature.

Muscidifurax raptorellus Kogan & Legner is a gregarious pteromalid ectoparasitoid that attacks pupae and pharate adults from several families of the higher Diptera. Egg-to-adult development time, adult parasitoid size and emerging offspring ( = secondary) sex ratio of M. raptorellus were compared with clutch size in two hosts that differed greatly in mass, the small Musca domestica Linnaeus and the larger Calliphora vomitoria Linnaeus. The mean number of emerging parasitoids did not vary significantly with host species, although slightly higher clutch sizes were recorded in C. vomitoria. Irrespective of offspring sex, parasitoids completed development more rapidly in M. domestica than in C. vomitoria. In the small host, the development time and adult size of M. raptorellus were negatively correlated with clutch size. By contrast, female parasitoid size was unaffected by clutch size in the larger host, C. vomitoria. In both hosts, female parasitoids were significantly larger than male parasitoids. The secondary sex ratio (percentage males) of emerging parasitoids was significantly lower in C. vomitoria, and varied with clutch size in both hosts. In C. vomitoria, the greatest proportion of females emerged from hosts with the highest clutch sizes, whereas in M. domestica hosts with the highest clutch sizes produced the lowest proportion of female progeny. The results described here show that the development of M. raptorellus is profoundly affected by interspecific differences in host quality. Our results suggest that mating structure and host quality have potentially different effects on sex ratio decisions in M. raptorellus, and perhaps other gregarious parasitoids.

Vertical polythene exclusion barriers combined with trapping out using pitfall traps have been used to create enclosures within which arthropod numbers can be manipulated. This technique has been primarily used to investigate the impact of ground-dwelling polyphagous arthropods on cereal pests. Arthropod numbers in a total of 42 enclosed areas were compared to adjacent unenclosed areas over three years in Hampshire, UK. A range of arthropod monitoring techniques was used, including pitfall traps, fenced pitfall traps and D-vac suction samples. The enclosures were effective in reducing most species of Carabidae, Linyphiidae and Lycosidae encountered and numbers in pitfall traps were reduced by an average of 74%, 62% and 77% respectively. Similar reductions in densities of these taxa were found. Staphylinidae were less effected with an average reduction of only 32% in pitfall traps, although Philonthus species were reduced by 82%. Results were compared to previous studies.

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.

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.

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.

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.

Laboratory-based experiments are presented involving two aphid sepcies (Myzus persicae Sulzer, a generalist and Brevicoryne brassicae Linnaeus, a crucifer specialist), and the predatory gall midge, Aphidoletes aphidimyza Rondani, on three cultivars of common cabbage Brassica oleracea var. capitata cv. Derby Day (green-leaved), Minicole (green-leaved) and Ruby Ball (red-leaved). In a laboratory-based tritrophic system including both species of aphid, the three cabbage cultivars and A. aphidimyza, predator both species of aphid, the three feeding on M. persicae or B. brassicae on cv. Derby Day, while growth was slowest separate experiment, A. asphidimyza larva feeding on B. brassicae on each of the three cultivars were significantly smaller and consumed less aphid fresh weight when maintained outdoors (mean temperature = 13.5°C) compared with a constant environment room (20°C). However, in this latter experiment under neither regime were differeneces in predator growth or consumption significant between cultivars. Effects of selective insecticides (pirimicarb and a neem seed kernel extract, NeemAzal-T/SR) on bitrophic (aphid-host plant) interactions were also investigated in the laboratory. A pirimicarb dose equating to c. 15% of the recommended field concentration caused equivalent toxicity of M. persicae on cv. Minicole compared with aphids treated with a three-fold greater dose and reared on cv. Derby Day. Cultivar-mediated differences in aphid mortality caused by the neem extract when tested for systemic and translaminar activity were not apparent. The results are discussed in relation to ways in which host plant selection, selective insecticides and biological control could potentially be manipulated and optimized in aphid management system on brassica crops.

Details of the life history, the effects of relative humidity and temperature on survival and reproduction, and the predatory ability of Aleurodothrips fasciapennis Franklin were examined under laboratory conditions. Stage-specific development and adult longevity were similar between sexes, and the adult sex ratio was 1:1. Females laid 23.3 ± 18.0 eggs of which 83% hatched. The survival rate of first instars to adulthood was 82%. The intrinsic rate of natural increase (rm) was 0.04, assuming a zero or 5.4 day pre-oviposition interval. Temperature did not affect the proportion of eggs that hatched, the proportion of first instars surviving to adulthood or adult sex ratios. However, female fecundity was dependent on temperature being highest at 24 ndash 28°C. Relative humidity did not affect adult sex ratio or female fecundity but the proportion of eggs hatched and the survival of first instars to adulthood increased as relative humidity increased. Few eggs hatched when relative humidity was <65%. Larval and adult female A. fasciapennis were voracious feeders but the number of prey killed per progeny was high, suggesting A. fasciapennis was inefficient at converting prey into progeny biomass. The potential value of A. fasciapennis as a biocontrol agent of Aonidiella aurantii (Maskell) on Australian citrus is discussed in terms of its rm, prey killing power and environmental adaptability. It is concluded that population growth of A. fasciapennis should exceed that of A. aurantii under field conditions but A. fasciapennis may be of little value against A. aurantii on citrus grown under conditions of high temperature and low humidity, or when prey densities are low.

Brightwell, R., Dransfield, R. D., Stevenson, P. and Williams, B. Changes over twelve years in populations of Glossina pallidipes and Glossina longipennis (Diptera: Glossinidae) subject to varying trapping pressure at Nguruman, south-west Kenya.

The correct mailing address for the authors is SNV Kenya, Ngong Lane, P.O. Box 30776, Nairobi, Kenya.