1. The behaviour of A. gambiae and A. melas in houses is described in relation to possible use of pyrethrum and DDT.

Pyrethrum.

2. Mass spraying of isolated villages with pyrethrum in kerosene four times a week reduces the day-time catch of Anopheles to one-third. The sporozoite rate of mosquitos in sprayed villages remains much the same as before treatment.

3. Observations in experimental huts with window traps attached show that pyrethrum exerts a repellent effect on many hungry Anopheles for a day or two after spraying, provided blood meals can be obtained easily in adjacent untreated houses.

4. Where all available huts occupied by man are sprayed, there is no great repellence to hungry mosquitos, which continue to feed in large numbers even in huts sprayed every day.

5. In untreated huts about 20 per cent. of the blood-fed females leave the house at dawn after feeding. In huts sprayed daily the proportion increases to about 80 per cent.

6. The fall in the house catch in villages sprayed 4–6 times a week is not due to any great reduction in the mosquito population, but to a shift from indoor to outside resting places.

7. As intense house spraying with pyrethrum fails to bring about any substantial reduction either in the mosquito population or in their infectivity, it is not likely to be of great anti-malaria value in West Africa.

DDT.

8. Mass spraying of village houses with 5 per cent. DDT in kerosene produces a dramatic fall in the day catch of resting Anopheles in houses. The catch remains very low for 4 weeks after treatment and it is still fairly low after 2 months.

9. Observations in experimental huts (fitted with window traps) treated with DDT in kerosene show that mosquitos may enter and feed within a few days of treatment. By the second week after treatment large numbers of Anopheles may feed every night in treated huts.

10. There is no evidence of mosquitos succumbing to the effects of DDT in kerosene inside the hut. Nearly all the Anopheles feeding in such huts leave after feeding and show no appreciable mortality in the following 48 hours.

11. The DDT in kerosene has a marked residual irritant effect on Anopheles, driving them out of the house after they have fed, and preventing mosquitos resting long enough on treated surfaces to absorb a lethal dose of DDT.

12. The few days complete protection from biting mosquitos which follows spraying inside the house with DDT in kerosene, is shown to be due mainly, if not entirely, to the repellent effect of the heavy dose of kerosene which accompanies the DDT.

13. Treatment of all rooms in an isolated village reduced the day catch to nil during 5 weeks after treatment. In outside resting places beside the village, bloodfed and gravid Anopheles, of which 2 per cent. had sporozoites in the salivary glands, Were taken regularly during this period.

14. The apparent elimination of mosquitos from houses following treatment of rooms with DDT in kerosene is due to a complete shift from inside to outside resting places, on account of the residual irritant, but not lethal, effect of DDT-in-kerosene treated surfaces.

15. The sharp fall in the house catch of Anopheles following treatment Of West African village houses with DDT in kerosene can not, therefore, be accepted as evidence of mosquito reduction or effective control.

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.

Opiine wasps are parasitoids of dacine fruit flies, the primary horticultural pests of Australia and the South Pacific. A taxonomic synopsis and distribution and host records (44% of which are new) for each of the 15 species of dacine-parasitizing opiine braconids found in the South Pacific is presented. Species dealt with are Diachasmimorpha hageni (Fullaway), D. kraussii (Fullaway), D. longicaudata (Ashmead), D. tryoni (Cameron), Fopius arisanus (Sonan), F. deeralensis (Fullaway), F. ferrari Carmichael & Wharton sp. n., F. illusorius (Fischer) comb. n., F. schlingeri Wharton, Opius froggatti Fullaway, Psyttalia fijiensis (Fullaway), P. muesebecki (Fischer), P. novaguineensis (Szépligeti) and Utetes perkinsi (Fullaway). A potentially undescribed species, which may be a colour morph of F. vandenboschi (Fullaway), is diagnosed but not formally described. Fopius vandenboschi sensu stricto, Diachasmimorpha fullawayi Silvestri, Psyttalia concolor Szépligeti and P. incisi Silvestri have been liberated into the region but are not considered to have established: a brief diagnosis of each is included. Biosteres illusorius Fischer is formally transferred to the genus Fopius. A single opiine specimen reared from a species of Bactrocera (Bulladacus) appears to be Utetes albimanus (Szépligeti), but damage to this specimen and to the holotype (the only previously known specimen) means that this species remains unconfirmed as a fruit fly parasite: a diagnosis of U. cf. albimanus is provided. Psyttalia novaguineensis could not be adequately separated from P. fijiensis using previously published characterizations and further work to resolve this complex is recommended. A key is provided to all taxa.

The effect of cover plants on arthropod functional biodiversity was investigated in a vineyard in Northern Italy, through a 3-year field experiment. The following six ground cover plants were tested: Sweet Alyssum; Phacelia; Buckwheat; Faba Bean; Vetch and Oat; control. Arthropods were sampled using different techniques, including collection of leaves, vacuum sampling and sweeping net. Ground cover plant management significantly affected arthropod fauna, including beneficial groups providing ecosystem services like biological control against pests. Many beneficial groups were attracted by ground cover treatments in comparison with control, showing an aggregative numerical response in the plots managed with some of the selected plant species. Alyssum, Buckwheat and ‘Vetch and Oat’ mixture showed attractiveness on some Hymenoptera parasitoid families, which represented 72.3% of the insects collected by sweeping net and 45.7 by vacuum sampling. Phytoseiidae mites showed a significant increase on leaves of the vineyard plots managed with ground covers, in comparison with control, although they did not show any difference among the treatments. In general, the tested ground cover treatments did not increase dangerous Homoptera populations in comparison with control, with the exception of Alyssum. The potential of ground cover plant management in Italian vineyards is discussed: the overall lack of potential negative effects of the plants tested, combined with an aggregative numerical response for many beneficials, seems to show a potential for their use in Northern Italy vineyards.

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.

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.

Triatomines are vectors that transmit the protozoan haemoflagellate Trypanosoma cruzi, the causative agent of Chagas disease. The aim of the current review is to provide a synthesis of the immune mechanisms of triatomines against bacteria, viruses, fungi and parasites to provide clues for areas of further research including biological control. Regarding bacteria, the triatomine immune response includes antimicrobial peptides (AMPs) such as defensins, lysozymes, attacins and cecropins, whose sites of synthesis are principally the fat body and haemocytes. These peptides are used against pathogenic bacteria (especially during ecdysis and feeding), and also attack symbiotic bacteria. In relation to viruses, Triatoma virus is the only one known to attack and kill triatomines. Although the immune response to this virus is unknown, we hypothesize that haemocytes, phenoloxidase (PO) and nitric oxide (NO) could be activated. Different fungal species have been described in a few triatomines and some immune components against these pathogens are PO and proPO. In relation to parasites, triatomines respond with AMPs, including PO, NO and lectin. In the case of T. cruzi this may be effective, but Trypanosoma rangeli seems to evade and suppress PO response. Although it is clear that three parasite-killing processes are used by triatomines – phagocytosis, nodule formation and encapsulation – the precise immune mechanisms of triatomines against invading agents, including trypanosomes, are as yet unknown. The signalling processes used in triatomine immune response are IMD, Toll and Jak-STAT. Based on the information compiled, we propose some lines of research that include strategic approaches of biological control.

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.

Three sites in south west Scotland, each having one deciduous and one coniferous woodland with populations of roe deer, were sampled over three years for Ixodes ricinus Linnaeus ticks using cloth drags. Nymphs and adult ticks were age graded by dissection of gut and Malpighian tubules and staining for lipid with Sudan red. Temperature and relative humidity were recorded in developmental and questing microclimates. Two annual cohorts of both nymphs and adults were found. For both instars one cohort became apparent in early spring and the other in autumn. The timing of the cohorts of nymphs corresponded to peaks of numbers questing, but neither females nor males had any clear seasonal pattern of questing. The maximum life of questing nymphs and adults was three to four months. Nymphs and adults were found questing at all months of the year and at temperatures ranging from 3.5°C to 29.3°C. Questing of larvae in summer peaks of numbers was positively correlated with temperature and negatively correlated with relative humidity. These results are explained by a descriptive model which invokes behavioural and morphogenetic diapause. Tests of the model are discussed and it is proposed that the main adaptive advantage of the complex life cycle is to permit moulting and oviposition to occur at favourable summer temperatures in ticks that have engorged at any time of the year.

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.

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.

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.

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.

The term ‘dead-end trap cropping’ has recently been proposed to identify a plant that is highly attractive for oviposition by an insect pest, but on which offspring of the pest cannot survive. The potential of the wild crucifer Barbarea vulgaris R. Br. to allure and serve as a dead-end trap crop for the diamondback moth Plutella xylostella (L.), an important pest of cruciferous crops worldwide, was examined in laboratory experiments. When P. xylostella adults were provided with a dual-choice of plants of B. vulgaris, and Chinese cabbage Brassica campestris (L.), in one arena, adult moths laid 2.5–6.8 times more eggs on the former than on the latter. When P. xylostella adults were provided with a dual-choice of plants of B. vulgaris and common cabbage Brassica oleracea L., adult moths laid virtually all their eggs on the former and ignored the latter. Nearly all P. xylostella eggs laid on the three species of plants hatched successfully, but nearly all individuals on plants of B. vulgaris died as neonates or early instar larvae, while 87–100% of the larvae on Chinese cabbage and common cabbage survived to pupation. Dual choice tests with a Y-tube olfactometer showed that volatiles from B. vulgaris were much more attractive to P. xylostella adults than those from common cabbage. The results demonstrate that B. vulgaris has a great potential as a dead-end trap crop for improving management of P. xylostella. Factors that may influence the feasibility of using B. vulgaris as a trap crop in the field are discussed, and ways to utilize this plant are proposed.

1. In Canada, European holly (Ilex aquifolium) can only be grown successfully in the mild, humid climate of western British Columbia. The sales of cut holly for decorative purposes amount to several hundred thousand dollars annually, and the tree is also in good demand for ornamental planting in public parks and private estates.

2. The most serious pest of holly in this part of the world is the Agromyzid fly, Phytomyza ilicis, or the Holly Leaf-miner, which was accidentally introduced from Europe without its attendant natural enemies. The larvae of this insect produce large unsightly blotches on the leaves which greatly lower the value of the cut foliage. As a rule 75 to 80 per cent. of the leaves are attacked in this manner.

3. Since chemical forms of restraint offered little hope of success, it was decided that the biological method of control should be given a trial. Accordingly, the writer undertook a general survey of the fly and its parasites in England, the results of which are described in the preceding pages. An account of the biological control of P. ilicis will be published in a separate paper at a later date.

4. A general account of the systematics, synonymy, distribution, host relationship, and biology of the holly fly itself precedes the parasite section.

The importance of colour in the attraction of Glossina palpalis palpalis (Robineau-Desvoidy) to trapping devices was investigated in the Ivory Coast. Biconical traps were tested with the normally royal blue lower cone replaced with one of 25 differently coloured cloths. Royal blues were consistently the best colours for traps; yellow and orange were the worst, catching less than 1% as many as the best royal blue. Modelling trap data from the spectral reflectivities of the colours used showed that blue wavelengths contributed positively, and ultraviolet and green-yellow-red negatively, to trap performance. The responses to screens were studied using electric nets, deployed to catch flies both circling around and landing on the screen. The overall catch (of circling and landing flies) was greatest for royal blue screens, intermediate for yellow and green ones, and lowest for screens highly reflective of ultraviolet light; the total range of variation between colours was much smaller than was the case with traps. The relationship of catch to spectral reflectivity was similar to that described for trap score. An achromatic series of screens (black, white and greys) all attracted significantly fewer females than did royal blue screens, implying that attraction to blue depends on colour discrimination and not on intensity contrasts alone. For most colours, the majority of flies circled the screen without landing; with materials strongly reflecting ultraviolet, however, a high proportion of flies (especially females) landed.

The continuous automatic monitoring of the aerial density, biomass and relative diversity of high-flying insect faunas has been made practicable by a new, vertical-looking radar. This inexpensive radar system, with its novel signal analysis capability, represents a major advance over earlier vertical-beam radars because it provides estimates of the body mass of individual overflying insects, as well as measurements of their direction and speed of movement. This paper summarizes data collected over a three-month period by the new radar in the height range from 150 m to c.1 km, over agricultural land in Worcestershire, England. The day-to-day variation in the numbers of insects and their altitudinal and diurnal patterns of flight activity are presented. Examples are also given of distributions of mass, displacement speed and direction, and orientation direction. The potential of the new radar for various research and operational monitoring tasks is briefly discussed.