Ecological communities used in biological pest control are usually represented as three-trophic level food chains with top-down control. However, at least two factors complicate this simple way of characterizing agricultural communities. First, agro-ecosystems are composed of several interacting species forming complicated food webs. Second, the structure of agricultural communities may vary in time. Efficient pest management approaches need to integrate these two factors to generate better predictions for pest control. In this work, we identified the food web components of an avocado agro-ecosystem, and unravelled patterns of co-occurrence and interactions between these components through field and laboratory experiments. This allowed us to predict community changes that would improve the performance of the naturally occurring predators and to test these predictions in field population experiments. Field surveys revealed that the food-web structure and species composition of the avocado community changed in time. In spring, the community was characterized by a linear food chain of Euseius stipulatus, an omnivorous mite, feeding on pollen. In the summer, E. stipulatus and a predatory mite, Neoseiulus californicus, shared a herbivorous mite prey. Laboratory experiments confirmed these trophic interactions and revealed that N. californicus can feed inside the prey nests, whereas E. stipulatus cannot, which may further reduce competition among predators. Finally, we artificially increased the coexistence of the two communities via addition of the non-herbivore food source (pollen) for the omnivore. This led to an increase in predator numbers and reduced populations of the herbivore. Therefore, the presence of pollen is expected to improve pest control in this system.

Variation in the effectiveness of biocontrol agents on the weed Parthenium hysterophorus L. was evaluated at two properties (Mount Panorama and Plain Creek) in Queensland, Australia for four years (1996–2000) using a pesticide exclusion experiment. At Mount Panorama, higher levels of defoliation by the leaf-feeding beetle Zygogramma bicolorata Pallister and galling by the moth Epiblema strenuana Walker in 1996–97 coincided with an above average summer rainfall, but in the following three years with below average summer rainfall the defoliation and galling levels were significantly lower. Biocontrol had significant negative impact on the weed only in 1996–97 with no major impact in the following three years. At Plain Creek, galling by E. strenuana was evident in all the four years, but varied significantly between years due to non-synchrony between P. hysterophorus germination and E. strenuana emergence. At Plain Creek biocontrol had limited impact on the weed in 1996–97 and 1997–98, with no significant impact in the following two years. Over the 4-year period, defoliation and galling resulted in 70% reduction in the soil seed bank at Mount Panorama, but the reduction in the soil seed bank at Plain Creek due to galling was not significant. Effectiveness of Z. bicolorata and E. strenuana was dependent on weather conditions and as a result had only limited impact on the weed in three out of four years.

The status and taxonomy of the west Palaearctic Pyrus-feeding psyllids are reviewed, and keys for the identification of adults and larvae are given. The species, now referred to the genus Cacopsylla, have been much confused. They are shown to comprise seven distinct species: C. pyrisuga (Förster), C. pyri (L.) (summer form pyrarboris, winter form pyri), C. pyricola (Förster) (summer form pyricola, winter form simulans), C. bidens (Šulc) (summer form vasilevi syn. n., winter form bidens), C. notata (Flor) sp. rev., C. permixta sp. n. (= simulans sensu Loginova and Gegechkori nec Förster) and C. fera (Baeva). Psylla horvathii Šulc and P. vicina Šulc are synonymized with C. pyricola; P. picta is regarded as a nomen dubium. Information is given on the host-plants and distribution of each species.

The functional response of the predatory mite Phytoseiulus persimilis Athias-Henriot to eggs of its prey, the spider mite Tetranychus urticae Koch was examined on three plant species. Experiments were done to determine whether differences in the functional response on the three plant species were due to the morphological features of the crop directly on the predator or through an effect of the plant species on the prey. The results show that crop morphology is the only factor influencing the predatory ability of P. persimilis on the three plant species. Fewer eggs were eaten on Ceanothus thyrsiflorus var. ‘Autumnal Blue’, the plant species with hairy leaves, and greater numbers of prey consumed on Choisya ternata, a species with smooth leaves. However, similarly few eggs were eaten on the smooth, but waxy leaved Euonymus japonicus as on Ceanothus thyrsiflorus, demonstrating that morphological characters of leaves other than the possession of hairs and trichomes may affect the rates of predation. The implications of these results for the tritrophic interactions between plant, predator and prey, and the development of suitable biological control strategies are discussed.

An intensive study was made of the ecology of species A and B of the Anopheles gambiae Giles complex at Kaduna, Nigeria, in October 1971. In collections comprising 383 larvae and 678 adult females from six villages, species A represented 82% of the larvae and 86, 89 and 91% respectively of the adult females caught by spray catches indoors, by biting catches outdoors and by exit traps fitted to windows. Larvae of species A and B occurred together in 42% of 57 breeding sites and showed no differential distribution among the various categories of site. Minor variations among the proportions of A and B females captured by different methods in the six villages showed no consistent contrasts. The only significant variation of the A/B ratio occurred at a temporary Fulani camp of cattle herdsmen, near Anguwun Maaza village, where an enhanced number of species B females were present indoors. At this Fulani camp a considerable number of both A and B females were feeding on cows outdoors and resting indoors during the day. Human blood indices of indoor-resting females were 88% for species A and 39% for species B at this camp, compared with 100% for both species at villages without cattle. Larval breeding places harboured an expectable range of insect predators. Predators of adult A. gambiae were not investigated although a predacious Emesine bug, Tinna elongata Villiers, was recorded in some huts. Numerous pathogen infections of larvae were observed, namely, Thelohania in 19%, Coelomomyces in 16%, unidentified gregarines in 7% and black-body virus in 3% of gambiae-positive breeding sites. Thelohania, Coelomomyces and gregarine infections were also encountered in adult females. Malaria sporozoite rates were 9·3% in species A and 5·5% in species B females. Some infections of stage III larvae of Wuchereria bancrofti were also seen in species A females.

The gypsy moth, Lymantria dispar Linnaeus, is one of the most serious insect pests of palaearctic and nearctic hardwood forests. We used amplified fragment length polymorphism (AFLP) to detect genetic diversity within and among gypsy moth populations. Five AFLP primer combinations were used on 98 L. dispar samples from different parts of Europe, Asia and North America, detecting a total of 481 polymorphic and 58 monomorphic fragments. Genetic similarities based on these data were calculated and cluster analysis was performed to graphically display groupings between isolates. Lymantria dispar individuals from close geographical areas of Europe were mostly grouped together in cluster analysis resulting in the formation of subgroups corresponding to the origin of the samples. Supporting this observation, clustering of individuals from 22 neighbouring populations in southern Germany agreed well with the region they originated from. Thus, AFLP analysis revealed the existence of a certain degree of genetic variability between European gypsy moth populations that could be explained by the accumulation of polymorphisms resulting from both historical population bottlenecks and the adaptation to different environmental conditions. The results of this study therefore demonstrate that AFLP analysis is a sensitive technique for distinguishing genotypes from different geographic origins as well as from neighbouring local populations and provides sufficient molecular markers for future characterization of the gypsy moth genome.

In small-scale experiments, the predatory mites, Hypoaspis aculeifer (Canestrini) and H. miles Berlese, applied at 700 mites m−2, and the entomopathogenic nematode, Steinernema feltiae (Filipjev) applied at 3 × 10−6 nematodes m−2 controlled sciarids and phorids in mushroom compost and casing substrates. For both mite species, earliest application to the growing substrate following sciarid infestation reduced sciarid emergence. In contrast, later application of each biological control agent provided more effective control of phorid emergence. The behaviour of adult mites suggested that H. aculeifer were more positively geotactic than H. miles although both species could penetrate compost and casing substrates to a depth of 2–12 cm. A majority of S. feltiae nematodes resided at a depth of 2–4 cm in both substrate types. Independent application of H. aculeifer provided more comprehensive control of sciarids and phorids than the other biological agents studied, owing to its better dispersal within compost and casing, and ability to attack larvae of differing ages.

Chironomids are excellent biological indicators for the health of aquatic ecosystems, but their use at finer taxonomic levels is hindered by morphological similarity of species at each life stage. Molecular markers have the potential to overcome these problems by facilitating species identification particularly in large-scale surveys. In this study, the potential of the polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) approach was tested to rapidly distinguish among chironomids within a geographic area, by considering chironomid species from Melbourne, Australia. By comparing molecular markers with diagnostic morphological traits, RFLP profiles of the cytochrome oxidase I (COI) region were identified that were specific to genera and some common species. These profiles were used to develop an RFLP–based key, which was validated by testing the markers on samples from several wetlands and streams. As well as allowing for rapid identification of species that are difficult to separate on morphological grounds, this approach also has the potential to resolve current taxonomic ambiguities.

Cephalonomia stephanoderis Betrem and Prorops nasuta Waterston are two bethylid parasitoids obtained from Africa for the biological control of the coffee berry borer, Hypothenemus hampei (Ferrari) in Mexico and Ecuador. Rearing methods and life-cycle studies carried out under controlled conditions are described for both the parasitoids and H. hampei. Scanning electron micrographs are shown of the developmental stages of the parasitoids. Data are given on development times, pre-oviposition period and on the mating and oviposition behaviour of C. stephanoderis.

In view of the fact that many blood-sucking Diptera are carriers of pathogenic micro-organisms of animals and human beings, the study of the structure of their mouth-parts has attracted the attention not only of zoologists but of medical men as well.

In Zimbabwe, cotton cloth dyed phthalogen blue attracted three times more Stomoxys spp. than Alsynite fibreglass panels. A single F3 trap caught nearly six times as many Stomoxys spp. as four Williams traps. The host odour component l-octen-3-ol (released at 0.6 mg/h) increased catches of Stomoxys spp. in an F3 trap (P < 0.05), but 4-methylphenol (0.7 mg/h) and 3-n-propylphenol (0.15 mg/h) did not (P > 0.05). Insecticide-impregnated targets did not appear to control a population of Stomoxys spp. attacking cattle. However, it is concluded that there is scope for the improvement of trapping and control systems for use against Stomoxys spp.

The deer ked (Lipoptena cervi) can fail in its host search. Host search fails when an individual deer ked irreversibly accepts a host unsuitable for its reproduction (e.g. a human) and drops its wings. In northern Europe, the main host of the deer ked is the moose (Alces alces). The deer ked is increasingly causing serious problems for humans (for example, causing deer ked dermatitis) and is considered a threat for the recreational use of forests. The adult deer ked flies in early and mid-autumn to search for a host. Our aims were: (i) to study whether there are ways to avoid deer ked attacks by wearing particular clothing, and (ii) to evaluate deer ked host choice. Using human targets, we explored the cues the deer ked uses for host selection. We studied which part of the host body deer keds target and if body colour and temperature affect their choice. In our experiments, deer keds landed more on dark and red clothing than on white clothing. Moreover, deer keds mostly attacked the upper body parts and preferred the back side of the body over the front side. Finally, deer keds preferred the warmest areas of the host.

Two acetylcholinesterase (AChE) variants, differing in sensitivity to inhibition by the organophosphorus (OP) insecticide paraoxon were identified in a population of Bemisia tabaci (Gennadius) from cotton in Israel using a single insect kinetic microplate assay. Two strains were established, homogeneous for one or other of the two variants, by isolating mated females from the field population onto individual cotton leaves, and testing a proportion of their female offspring to identify their AChE genotype. Polyacrylamide gel electrophoresis of their I-naphthyl butyrate hydrolyzing esterases showed that all insects contained esterase E0 14, which is indicative of B-type whiteflies, although the staining intensity of this band differed. Resistance to the OPs monocrotophos, profenofos and chlorpyrifos in leaf dip bioassays was consistent with the presence of the insensitive AChE. The data also indicated that separate mechanisms conferred resistance to the two pyrethroids cypermethrin and bifenthrin. The former, when used in a mixture with profenofos, was no more toxic than when the OP was used alone, and resistance to the mixture was largely dependent on the presence of the insensitive AChE.

1. An attempt has been made to elucidate the confusion existing about the biology, morphology and nomenclature of the Oat-Apple Aphis, Rhopalosiphum prunifoliae, Fitch. A close study of the problem confirms the observations made by Börner that at least two distinct species have in the past been included under the name of R. prunifoliae. The names Rhopalosiphum padi, L., and Rhopalosiphum crataegllum, Theo., are adopted for these species.

2. Detailed descriptions and figures of the different generations are given and a comparison shows that the two species can readily be distinguished from one another.

3. R. padi appears to be of greater importance as a cereal pest than R. crataegllum. The latter species is a widespread pest of pip-fruit.

4. An account is given of the overwintering of R. padi on Prunus padus, and the results of experiments on estimating the size of the ova-populations is shown.

The author is indebted to Mr. R. A. Harper Gray for allowing him facilities to carry out the investigation; also to Mr. J. A. Dunn for assistance in collecting some of the material and much general help.

i. A four-year survey, involving the investigation of over 1,000 cases of strike, has been made of the species concerned in sheep myiasis throughout the British Isles. In all regions, L. sericata is the principal maggot-fly. In Scotland, Northern England and North Wales, L. caesar is an important species. Phormia terraenovae has much the same distribution, as a striking species, as L. caesar, except that it apparently does not strike sheep in North Wales ; in the areas where it occurs it follows L. caesar in importance. These two species are apparently capable of acting as primary flies. Calliphora erythrocephala, and, more rarely, Calliphora vomitoria occur fairly generally over the country, but only in very low incidence. Larvae of Muscina spp. have been recovered from only three cases, one each in Scotland, England and Ireland. The two closely related species, L. caesar and L. illustris have only been separated in a few instances, and there is not sufficient evidence for the latter species, but it would seem to be more common in lowland areas than in the north and west.

ii. The incidence of “ alternative ” species, i.e. species other than L. sericata, decreases from north-west to south-east of Britain ; they occurred in 47 per cent. of strikes north and west of a line from Inverness to Glasgow, and in over 20 per cent. of the cases between this and a line from East Lothian to Morecambe Bay, south of the Lake District. In the fringe of hill country east and south of this, e.g., the Cheviots, Pennines and Wales, about 10 per cent. of cases contained “ alternative ” species. Farther to the south-east and south “ alternatives ” were rare.

iii. Within the above belts of territory, the “ alternative ” species appear to have certain common regions which are favourable for the striking habit, although the limits of strike-distribution for each species are apparently not quite coincident. These “ favourable regions ” are discussed in the text. With Phormia terraenovae the habit appears to be restricted to favourable regions, where it occurs in moderately high incidence ; with L. caesar strike occurs in relatively high incidence in favourable regions, but is also present, in low proportion, throughout the country, while the Calliphora species strike in low proportion in favourable regions, and sporadically elsewhere.

iv. Phormia and L. caesar have a higher relative incidence in the first half of the fly season than in the later half ; C. vomitoria may be restricted to the extremes of the season-May, June and September.

Large-scale eradication campaigns against tsetse flies Glossina spp. are giving way to smaller operations aimed at disease and vector containment. There has been little discussion of the effects of these changes in policy. This study estimates the rate at which tsetse re-infect treated areas after the termination of control efforts. Movement is modelled as a diffusion process with a daily root mean square displacement (λ) of 0.2–1 km−1/2 and population growth as logistic with a growth rate (r) ≤1.5% day−1. Invasion fronts move as the product of λ and √r. For r = 0.75% day−1 a front advances at 2.5 km year−1for each 100 m increment in λ. If there are 0.001% survivors in 10% of the treated area, the population recovers to within 1% of the carrying capacity (K) within three years. If the control area is subject to invasion from all sides, a treated block of 10,000 km2 is effectively lost within two years – except at the lowest values of λ and r. Cleared areas of 100 km2 are lost in a year, as observed in a community-based suppression programme in Kenya. If the treated area is closed to re-invasion, but if there is a block where tsetse survive at 0.0001–0.1% of K, the population recovers within 3–4 years for up to 20 km outside the surviving block. If the surviving flies are more widely spread, re-infection is even more rapid. The deterministic approach used here over-estimates re-invasion rates at low density, but comparisons between control scenarios are still valid. Stochastic modelling would estimate more exactly rates of re-infection at near-zero population densities.

DNA-based techniques have proved to be very useful methods to study trophic relationships between pests and their natural enemies. However, most predators are best defined as omnivores, and the identification of plant-specific DNA should also allow the identification of the plant species the predators have been feeding on. In this study, a PCR approach based on the development of specific primers was developed as a self-marking technique to detect plant DNA within the gut of one heteropteran omnivorous predator (Macrolophus pygmaeus) and two lepidopteran pest species (Helicoverpa armigera and Tuta absoluta). Specific tomato primers were designed from the ITS 1–2 region, which allowed the amplification of a tomato DNA fragment of 332 bp within the three insect species tested in all cases (100% of detection at t=0) and did not detect DNA of other plants nor of the starved insects. Plant DNA half-lives at 25°C ranged from 5.8 h, to 27.7 h and 28.7 h within M. pygmaeus, H. armigera and T. absoluta, respectively. Tomato DNA detection within field-collected M. pygmaeus suggests dietary mixing in this omnivorous predator and showed a higher detection of tomato DNA in females and nymphs than males. This study provides a useful tool to detect and to identify plant food sources of arthropods and to evaluate crop colonization from surrounding vegetation in conservation biological control programs.

Growing interest in biodiversity and conservation has increased the demand for accurate and consistent identification of arthropods. Unfortunately, professional taxonomists are already overburdened and underfunded and their numbers are not increasing with significant speed to meet the demand. In an effort to bridge the gap between professional taxonomists and non-specialists by making the results of taxonomic research more accessible, we present a partially automated pattern recognition system utilizing artificial neural networks (ANNs). Various artificial neural networks were trained to identify spider species using only digital images of female genitalia, from which key shape information had been extracted by wavelet transform. Three different sized networks were evaluated based on their ability to discriminate a test set of six species to either the genus or the species level. The species represented three genera of the wolf spiders (Araneae: Lycosidae). The largest network achieved the highest accuracy, identifying specimens to the correct genus 100% of the time and to the correct species an average of 81% of the time. In addition, the networks were most accurate when identifying specimens in a hierarchical system, first to genus and then to species. This test system was surprisingly accurate considering the small size of our training set.

Aphids belonging to the species Nasonovia ribis-nigri (Mosley), Aulacorthum circumflexum (Buckt.), Macrosiphum euphorbiae (Thos.), Myzus persicae (Sulz.) and A. solani (Kalt.) were exposed to attack by the parasite, Monoctonus paludum Marshall, and were sectioned and dissected at various time-intervals after attack in order to observe the developmental processes of the parasite.

The egg was always laid in the posterior mass of fused ventral nerve ganglia in the thorax of the aphid host.

The development of the parasite in N. ribis-nigri, its normal host on lettuce, is described.

In the species A. circumflexum the development of the parasite was arrested after approximately 24 hours by the secretion around it of a thin brown capsule formed by certain of the host's blood cells.

In the other three species, Macrosiphum euphorbiae, Myzus persicae and A. solani, no capsule formation occurred. The development of the parasite embryos was rather variable in these but it was common for parasites in Macrosiphum euphorbiae to reach the stage normal for 24-hour embryos and for parasites in Myzus persicae and A. solani to reach stages rather less advanced than this before degenerative changes set in.

The degenerative changes in the parasite embryos are described for each species of aphid and the nature of these changes is discussed.