Cacopsylla pyricola (Förster) is one of the most important pests of pear in North America, where several native predators have been considered for integrated pest management (IPM) programmes. Two molecular markers of 271 and 188 bp were developed from C. pyricola cytochrome oxidase I (COI) fragments, in order to study the detection of this species in the gut of arthropod predators. Primer sensitivity and the detection period for pear psylla remains in the guts of Anthocoris tomentosus Pericart were determined. The sensitivity threshold was defined at 10-5 dilution of a C. pyricola fifth-instar nymph in all samples. Predator adults were evaluated immediately after ingestion of one to five C. pyricola nymphs (t = 0) and after 2, 4, 6, 8, 16, 24 and 32 h. Detection of the presence of C. pyricola DNA always lasted longer using the shorter fragment and was observed after 32 h of digestion using both markers. The primers amplifying the 188 bp fragment amplified all four psyllid species tested, whereas the primers designed to amplify the 271 bp fragment did so exclusively for C. pyricola and its close relative, Cacopsylla pyri (Linnaeus). Both primers failed to amplify DNA from representative species of the Coccinellidae, Chrysopidae, Hemerobiidae, Anthocoridae, Miridae, Salticidae, Aphididae, Tetranychidae and the Tortricidae, suggesting their suitability for general trophic studies.

Almost all of the studies here reported were made in one small region, so that very little new information was secured on the ranges of the species of mosquitos under consideration.

Our investigations regarding breeding-places were limited to a few species. Aëdes vittatus was found occasionally breeding in tree-holes in Ibadan. Aëdes irritans adults were taken at Ibadan, which is so far inland that this species must sometimes breed in places other than crab-holes at the edges of salt or brackish water. We did not, however, find the larvae of this species at Ibadan. The favourite breeding-place of Eretmopodites chrysogaster was found to be small collections of water in fallen leaves (especially those of cocoa trees) lying in moist and densely shaded places. Because of the abundance of Mansonia africana in places practically free from Pistia, we conclude that in the vicinity of Lagos it must breed abundantly on other plants. The long flight range of this species was taken into consideration in arriving at this conclusion. An extensive search failed, however, to reveal these plants. M. uniformis, also abundant in the vicinity of Lagos, does not breed there upon Pistia, but an extensive search failed to reveal its breeding-place.

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama is considered a key citrus pest due to its role as vector of ‘huanglongbing’ (HLB) or citrus greening, probably the most economically damaging disease of citrus. Insecticidal control of the vector is still considered a cornerstone of HLB management to prevent infection and to reduce reinoculation of infected trees. The severity of HLB has driven implementation of intensive insecticide programs against ACP with unknown side effects on beneficial arthropod fauna in citrus agroecosystems. We evaluated effects of calendar sprays directed against this pest on natural enemy assemblages and used exclusion to estimate mortality they imposed on ACP populations in citrus groves. Predator exclusion techniques were used on nascent colonies of D. citri in replicated large untreated and sprayed plots of citrus during the four major flushing periods over 2 years. Population of spiders, arboreal ants and ladybeetles were independently assessed. Monthly sprays of recommended insecticides for control of ACP, adversely affected natural enemy populations resulting in reduced predation on ACP immature stages, especially during the critical late winter/early spring flush. Consequently, projected growth rates of the ACP population were greatest where natural enemies had been adversely affected by insecticides. Whereas, this result does not obviate the need for insecticidal control of ACP, it does indicate that even a selective regimen of sprays can impose as yet undetermined costs in terms of reduced biological control of this and probably other citrus pests.

In surveys of cassava fields in the coastal savanna and rain forest zones of Ghana, eight species of ants, mostly in the genera Camponotus, Crematogaster and Pheidole (Hymenoptera: Formicidae), were found attending cassava mealybug, Phenacoccus manihoti Matile-Ferrero. Ant densities were much higher in the rain forest than in the savanna and, in most zones, positively correlated to mealybug population densities. Pheidole megacephala (Fabricius) was the only species more abundant in the interior of fields, whereas the other species preferred the edges of fields or, like Camponotus spp., did not respond to edge effects. Weediness of the fields did not clearly influence the presence of ants. Crematogaster sp. and P. megacephala spent most of the time on cassava tips, where they built carton tents. Ants of the three genera reduced parasitism rates by the exotic Epidinocarsis lopezi (De Santis) (Hymenoptera: Encyrtidae) to half, compared to the rates observed on mealybug colonies of equal size that were not attended. Hyperparasitism by Prochiloneurus insolitus (Alam) (Hymenoptera: Encyrtidae) and Chartocerus hyalipennis Hayat (Hymenoptera: Signiphoridae) and predation by the indigenous Exochomus troberti Mulsant (Coleoptera: Coccinellidae) were similarly reduced. Where ants were excluded experimentally by insectcide barriers, parasitism was 32%, compared to only 10% in the control, and predator densities were reduced three-fold. In a 24 h experiment, Pheidole megacephala was observed to remove about half the E. troberti larvae; Crematogaster sp. and Camponotus spp. were less efficient. The results show the locally strong interference of ants with biological control of the cassava mealybug. Despite this interference, mealybug populations in the rain forest were judged to be below damaging levels.

Morphological variation in nine characters of 157 clones of Myzus persicae(Sulzer) was examined by multivariate analysis. The clones were collected from peach, Prunus persica, the primary host and the secondary hosts tobacco, Nicotiana tabacum, cabbage, Brassica oleracea, sugarbeet, Beta vulgaris and pepper Capsicum annuum. The 156 clones originated from various regions of Greece, both in the north, where a large part of the population has an annual bisexual generation on peach, and in more southerly regions, where populations are predominantly unisexual. One clone was collected from tobacco in Caserta, Italy. All clones were laboratory-reared on potato. Canonical variate analysis, hierarchical cluster analysis and a non-parametric classification tree method both revealed morphological differences associated with the host-plant on which they were collected. The scores of the first two canonical variates separated the tobacco-feeding clones from those originating from other secondary host-plants. However, in tobacco-growing areas the tobacco-feeding form predominated in spring populations on peach, and was sometimes found on other secondary hosts. In addition, using cluster analysis, the clones from tobacco which were sampled in the most southeasterly region showed a relatively large phenotypic distance from those collected further north and west. Moreover, clonal phenotypes were affected both by host plant and by long-term parthenogenetic rearing. However, in spite of these effects, the tobacco form was generally distinguishable from aphids originating from other hosts, indicating that the difference must have a genetic basis. In separate analyses of the clones originating from secondary hosts no association was found between morphology and either life cycle category or colour. Discriminant analysis showed that 89% of 1723 specimens could be correctly classified into the two groups.

The brackish water form of A. gambiae on the East African coast—and probably in Mauritius—is not the same as A. melas of West Africa.

In salt-water gambiae a variable proportion of the females have an additional dark band on the palps, resembling 4-banded melas, but the remainder are indistinguishable from typical gambiae.

Eggs and larvae of salt-water gambiae show no morphological differences from those of fresh-water gambiae, thereby differing from A. melas of West Africa.

Larvae of the two forms show a clear-cut difference in reaction to sudden changes in salinity, and a simple test has been worked out whereby wild-caught females can be accurately identified by the reactions of their progeny.

This physiological test has formed the basis of all work in comparing the incidence, habits, and infectivity of salt and fresh-water gambiae in Dar-es-Salaam.

Exposed to equal chances of infection in the same village during 1947 and 1948, fresh-water gambiae had a sporozoite rate of 9·4 per cent. while that of salt-water gambiae was 0·8 per cent.

About 4 per cent, of both forms were infected with filaria larvae, but monthly figures showed that infection rates in salt-water gambiae may rise to 22 per cent.

Fresh-water gambiae show little tendency to leave African houses at dawn after feeding, whereas in salt-water gambiae over one-third of freshly blood-fed females leave the house at dawn.

In fresh-water gambiae many half-gravid females leave the shelter of the house at dusk on the night after the blood feed. There is no marked difference in infectivity between those which leave the hut and those which remain indoors at this stage.

Blood-fed and gravid females of fresh-water gambiae, funestus, and salt-water gambiae have been found in outdoor resting places, gravid females predominating in the case of the first two.

Although larvae of salt-water gambiae can complete their development in pure sea water, in nature increasing salinity becomes a limiting factor before it reaches that of sea water, continuous breeding being no longer possible at salinities over 83 per cent. sea water.

Salinity as a limiting factor explains the rather restricted breeding of salt-water gambiae on the coast, and suggests that certain coastal fresh-water swamps at Dar-es-Salaam could be cleared of all Anopheline breeding by salinifying with sea water.

Sites in the humid forest of Cameroon and the derived savanna of Benin were selected to evaluate the effect of planting border rows of wild host plants on lepidopterous stem-borer infestations and on maize yield. Grass species were chosen that in surveys and greenhouse trials were highly attractive to ovipositing female moths but with offspring mortality of close to 100%, thus acting as trap plants. In Cameroon, elephant grass Pennisetum purpureum Moench significantly lowered infestations of Busseola fusca (Fuller), Sesamia calamistis Hampson and Eldana saccharina Walker and increased yields of maize though the differences were not significant during all three cropping seasons. In 1998 in Benin, the only grass tested, Pennisetum polystachion L., significantly increased parasitism of mainly S. calamistis eggs by Telenomus spp. and larvae by Cotesia sesamiae Cameron and reduced numbers of the cob-borer Mussidia nigrivenella Ragonot. In 1999, three grass species; P. polystachion, Sorghum arundinaceum (Desv.) Stapf and Panicum maximum Jacq. were tested. Panicum maximum was the most efficient species for suppressing S. calamistis and M. nigrivenella infestations and enhancing egg and larval parasitism. In the Benin trials, with the exception of M. nigrivenella damage to cobs, the grass species tested had no beneficial effect on yield because pest densities were too low and also rodent damage to maize was enhanced with grasses in the vicinity of the crop. By contrast, stand losses due to Fusarium verticillioides Sacc. (Nirenberg), were significantly reduced by border rows of grasses.

Cyrtobagous singularis Hust. was recorded from Brazil, Paraguay, Uruguay and Argentina in association with six species of Salvinia (aquatic ferns). Field observations and laboratory studies in Brazil and Australia showed that C. singularis severely damaged S. molesta and that the weevil is suitable as a control agent for this weed in tropical and subtropical areas in Australia. In host-specificity studies using 46 plant species that occur in Australia, development of the immature stages took place only on S. molesta. Minor leaf scarring occurred on sweet potato when in contact with water, but starvation tests excluded this plant as a possible terrestrial host. Adults fed, but were unable to reproduce, on water lettuce (Pistia stratiotes). The high degree of host specificity indicated that establishment of this weevil in Australia is without risk to non-target plants. C. singularis was first released and became established in Australia in 1980.

The activity of detoxifying enzymes (glutathione-S-transferases (GST), mixed-function oxidases (MFO), and esterases (EST)) and the presence of insensitive variants of target proteins (sodium channel and acetylcholinesterase) were examined in individual male and female codling moths. Twenty-nine populations from 11 countries and two laboratory strains were examined. Populations were classified as either unsprayed or sprayed. The ranges of enzyme activities across field populations varied 15-fold, 485-fold and fourfold for GST, MFO and EST, respectively. MFO was the only enzyme whose activity differed in a binomial classification of orchards based on their spray history. Few differences in enzyme activities were found due to sex among populations; and, in these cases, males had higher GST and lower MFO and EST activities than females. Activities of the three enzymatic systems across all populations were positively correlated. Populations from Greece, Argentina and Uruguay had significant percentages of moths with elevated GST and MFO activities. The co-occurrence of moths expressing both elevated MFO and low EST activities was found in conventional orchards from the Czech Republic and France. Chile was the only country where populations from treated orchards did not include a significant proportion of individuals with enhanced enzyme activity. The kdr mutation was found at significant levels in ten populations from five countries, including all French and Argentinean populations. The mutation in AChE was only detected in the Spanish population.

The sugarcane borer, Diatraea saccharalis (F.), is a pest of graminaceous crops in the southern USA, including sugarcane, maize, and rice. This study was conducted to investigate the effect of silicon (Si) soil amendments on performance of sugarcane borer, D. saccharalis, on two rice cultivars, Cocodrie and XL723. There was a significant increase in the Si content of rice plants supplemented with calcium silicate as compared to non-treated plants. Soil Si amendment led to lower relative growth rates (RGRs) and reduced boring success of sugarcane borer larvae. Effects of soil Si amendments on borer success and RGR appeared to be more pronounced in ‘Cocodrie’, the cultivar relatively susceptible to borers, than in the moderately resistant cultivar, XL723. Soil Si amendment may contribute to the management of D. saccharalis through reduced feeding injury and increased exposure to adverse environmental conditions and natural enemies arising from reduced boring success.

1. Collections of Cydia pomonella were made in France in 1928 and 1929–30.

2. The numbers of moths and parasites that emerged from the collections are given.

3. The biology and host-lists of the parasites are dealt with, and information on the larval anatomy is given.

4. Low percentages of parasitism of the larvae were found, and it is concluded that predacious birds, and the removal of larvae with the crop, must be important factors in the control of the Codling Moth in France.

There are three moth-borers of sugar-cane in Mauritius, Proceras sacchariphagus Boj. (Crambid.), Sesamia vuteria (Stoll) (Agrotid.) and Olethreutes schistaceana (Snell.) (Olethreutid.).

The eggs of all three are parasitised by Trichogramma sp. ? australicum Gir., while a second undetermined species of Trichogramma parasitises the eggs of Sesamia and Olethreutes. Sesamia eggs are also parasitised by a Scelionid, Platytelenomus sp. ? hylas Nixon.

Several aspects of the biology of the tomato moth, Lacanobia oleracea (Linnaeus) were investigated when these insects were fed an artificial diet and kept under laboratory conditions. The six larval stadia occupied a total period of 35.6 days at 20°C and 65% r.h. Larvae of each stadium could be separated by their head capsule widths, but not weight ranges, which overlapped. Feeding studies carried out on larval L. oleracea revealed instar dependent changes in the indices of food consumption and utilization. Larvae increased in weight from the fourth to sixth instar due to a combination of the increased efficiency with which ingested food was converted to body tissue, and increased food consumption by older larvae. Sixth (final) instar larvae exhibited three distinct behavioural phases; during one of these, the feeding phase, larvae consumed a greater amount of diet than either the fourth or fifth instars. The mean pupal period of non-diapausing pupae was 25 days. Pupal diapause was induced when larvae were reared under short day conditions. The male to female sex ratio of adult moths was 1:1.3. Mating generally began during the first scotophase after adult eclosion, and stopped soon after the start of the next photophase. Females usually mated only once, but males were capable of mating at least seven times. Oviposition normally commenced on day 2 of adult life, and the mean total egg production was 1186 eggs/female. Sex pheromone components were not present in solvent extracts of the pheromone glands of 20-day-old female pupae, but low levels were detected in pharate adults. A further increase in pheromone levels in newly-emerged moths was detected and, in isolated virgin moths, pheromone levels increased each day of adult life until day 9. Pheromone levels were significantly lower in two-day-old mated adult females, than in two-day-old virgins.

Details are given of a trap for Phlebotomine sandflies attracted to a small mammal placed in a cage incorporated in the trap. It was developed in British Honduras for the purpose of studying the sandflies attracted to proven or possible hosts of Leishmania, other than man. The results of initial tests carried out at Central Farm from November 1964 to February 1965 are reported. These provided evidence that the sandflies caught in the trap were attracted to the rodents used as bait, and did not enter by chance; unbaited traps caught virtually no flies. In traps baited with rodents known to be reservoir-hosts of Leishmania, the species caught in greatest numbers was Phlebotomus apicalis Floch & Abonnenc, and amongst those caught in smaller numbers were P. cruciatus Coq. (including P. diabolicus Hall) and P. deleoni Fairchild & Hertig; it is suggested that all three are possible vectors of leishmaniasis in British Honduras. The relative numbers of the sandfly species caught in the traps were very different from those caught on man in British Honduras and by direct catching on animals in Panama.

Females of Anopheles darlingi Root were the commonest (98·6%) of 5464 anophelines taken in 866 man-hours of human bait catches at night, in or near houses in the rain forest in Suriname during 1979–81, but their abundance could not be related to the prevalence of human malaria. In most endemic areas, few females were taken. At Aseli Kamp (4°17'N, 53°24'W) on the Lawa River, biting females were most abundant from April to June, during the long rainy season and rare or absent from September to March, during the long dry, short rainy and short dry seasons. At Apoma Tapoe, however, only 40 km downstream, they were most abundant in october and November, during the long dry season. Females entered houses to feed, with peak biting activity between 22·00 and 23·00 h, and were observed to rest near the collector for a mean of 7·7 min before and 17·1 min after feeding. No females were found resting by day, in buildings or out of doors. The mean parous rate of 827 females from biting catches was 43·6%. The expected biting rate of females was reduced by 20·3% in a house for six nights after it had been sprayed with DDT wettable powder (2 g/m2 active ingredient), and by a mean of 82·6% during seven nights in a camp where the edge of the surrounding forest was sprayed with an ultra-low-volume mist of 95% fenitrothion (1·3 ml active ingredient per metre of perimeter) on the first, third and sixth days. A. darlingi larvae were found at Aseli Kamp in all seasons along the river's edge between water hyacinth plants (Eichhornia) and floating debris, and during the long rains in flooded forest.

The impact of Phenacoccus manihoti Matile-Ferrero on growth and tuber yield of cassava, and the results of its biological control by the exotic parasitoid Epidinocarsis lopezi (De Santis) were investigated in a survey of 60 farmers' fields in Ghana and Ivory Coast over an area of 180 000 km2 of the savana and forest ecosystems. Twenty-nine variables associated with plant growth, agronomic and environmental factors, and insect populations were recorded. Densities of P. manihoti were closely correlated with stunting of the cassava shoot tips and, less so, with the rate of stunting early in the growing season. With increasing mealybug infestations, average harvest indices declined and populations of E. lopezi and of indigenous coccinellids increased, but parasitoids were found at lower host levels than were predators. The length of time E. lopezi had been present in an area was the most important factor influencing mealybug densities. Thus, P. manihoti populations were significantly lower where E. lopezi had been present for more than half the planting season than in areas where E. lopezi was lacking or had been only recently introduced. A significant proportion of the farmers in the savanna zone, where P. manihoti populations were much higher than in the forest zone, had observed this decline due to E. lopezi. Tuber yield losses due to P. manihoti in the absence of E. lopezi were tentatively estimated at 463 g/plant in the savanna zone. No significant effect was found in the forest region. When E. lopezi was present, average P. manihoti damage scores were reduced significantly, both in the savanna and forest regions. The increase in yields was 228g/plant or about 2.48 t/ha in the savanna region.

Based on data collected during regular, biconical trap sampling of Glossina palpalis palpalis (R.-D.) over two and a half years during and after two insecticide programmes in Ivory Coast, various analytical techniques were developed which allow the estimation of mortality rates and life-time fertility from ovarian age distributions of female flies. Data from trapping-out experiments were used to calculate the natural resilience of local populations. The results reveal that the dynamics of the populations showed considerable local variation, with two major types of sites. At those sites with large numbers of domestic pigs, the fly population was dense and showed a high degree of natural resilience and a low mean mortality rate, so that it could be selfsustaining through reproduction alone. At sites with few pigs, the fly population was scarce and showed a lower degree of natural resilience and a higher mean mortality rate such that the population could only be maintained by continuous input of immigrant flies. Studies of the natural dynamics of tsetse can be used to predict the likely effectiveness of alternative control schemes; fly mortality rates must be permanently increased in order to reduce fly numbers or infection rates to below some threshold for disease transmission.

The ecology of the adult mosquitos of the Northern Guinea Savannah was studied from 1960 to 1962 in the Kaduna area mainly in two Hausa villages, Anguwun Rimi and Kangimi, and in nearby Fulani settlements. A description of the area and various types of village huts is given together with an account of the climate and meteorological data. Emphasis was on the Anophelines and their relation to malaria but at the same time information on the Culicines is presented.

Biting catches, in which mosquito scouts acting as human bait collected adults in test-tubes, were performed for over a year in A. Rimi. A total of 38 species was caught in these collections, but many appeared only infrequently. By far the commonest mosquito biting man was Anopheles gambiae Giles which had its peak density towards the end of the rains, in September, and although its population was greatly reduced during the dry season it however remained the principal anthropophilous species. In the area in which the catches were performed A. nili (Theo.) was the second commonest mosquito, and with the exception of March it was more abundant than A. funestus Giles. In other areas it was not so common, and in Kangimi A. funestus was almost as abundant during the rains as A. gambiae, and at the beginning of the dry season it became the main Anopheline. Most of the other Anophelines that were taken at bait were only caught in any numbers during the latter part of the wet season; for the remainder of the year they were virtually absent. Mansonia uniformis (Theo.) was abundant in October, but for the rest of the year it was rarely taken; M. africana (Theo.) was found to be uncommon in the area. Due to the close proximity of Kaduna to A. Rimi, Culex pipiens fatigans Weid., a species now associated with urbanisation and not with villages, was common. Both bait catches and pyrethrum spray-sheet collections in houses showed that it greatly increased in numbers at the beginning of the rains, but that this high level of density was not maintained, and during the greater part of the wet season the species was less common than in the early rains. Aedes aegypti (L.) sens. lat. was rare both in houses and in bait catches; the two principal Aedes species were Ae. vittatus (Big.) and Ae. furcifer (Edw.); the latter species is confined to the Savannah zones. The biting cycles of the three main Anophelines were characterised by maximum feeding occurring after midnight. In both A. gambiae and A. nili there were two main peaks, between 2400 and 0100 and between 0300 and 0400 hr.; in A. funestus, maximum biting occurred between 2400 and 0200 and between 0300 and 0400 hr.

By the use of mosquito nets baited with humans, both inside huts and out of doors, the relative attractiveness, to the anthropophilous Anophelines, of man in the two situations was assessed. It was found that A. nili was equally attracted to man in both situations, and although slightly greater numbers of A. gambiae and A. funestus were found biting out of doors, for practical purposes man is equally attractive in both places. Certain species, notably A. coustani Lav. sens, str. and A. hancocki var. brohieri Edw., were rare or absent in the inside and outside bait-net collections, whereas they were readily taken in both situations in test-tube catches performed in the same locality on the same nights. In fact, more specimens of A. coustani sens. str. were taken in the outside test-tube catches than of either A. funestus or A. nili, and A. hancocki var.brohieri was commoner than A. funestus.

Catches of adults from mud walls and thatch roofing of typical round village huts showed that there was generally no appreciable difference in the attractiveness of these two surfaces to either A. gambiae or A. funestus, but as the thatch only comprised about 34–44 per cent, of the internal surface area of the huts the absolute number resting on the walls will be greater than on the roof.

Spray-sheet collections showed that besides large numbers of A. gambiae and A. funestus resting; during the day-time in normal mud-walled living huts of the Hausa, high densities of these species were found in the Fulani huts, which do not incorporate any mud in their design, and moderate numbers were also caught in Hausa villages in the zaures (huts resembling living ones, but without doors, furniture or fires and not normally slept in at night). Collections from outdoor resting places demonstrated that considerable day-time resting occurred in uninhabited huts, under eaves of huts, both inside and under eaves of goat stables, in kitchens, amongst the tightly woven grass mats termed ‘ zana ’ matting, in rodent holes, tree holes, pots, near wells, amongst grass and vegetation and underneath and under the eaves of grain bins. Surprisingly few examples of A. nili were found in any of the outside resting shelters examined, despite the fact that both exit traps and spray-sheet collections showed that it bit freely in huts but rarely stayed in them. The large number of A. gambiae and A. funestus found out of doors, coupled with the exodus of blood-fed individuals from huts, showed that an appreciable amount of exophily occurred in both species. Entrance traps fitted to village huts caught, in addition to unfed, both blood-fed and gravid (taken to include half-gravid and full-gravid) females of A. gambiae and A. funestus, suggesting that a certain amount of exophagy and re-entry of gravid individuals was occurring. Numerous precipitin tests were made on blood-meals obtained from A. gambiae, A. funestus and A. nili. and a few also from most of the other species. Results showed that the three principal Anophelines were strongly anthropophilous but the exophilous population of A. funestus and A. gambiae showed some deviation to other vertebrates. Most of the other Anophelines, e.g., A. rufipes (Gough) sens, lat.,A. hancocki var. brohieri, A. flavicosta Edw. and A. longipalpis var.domicolus Edw., found resting in goat shelters and other outdoor sites had fed mainly on other vertebrates.

On account of the already available information on the infectivity of both A. gambiae and A. funestus in Northern Nigeria, dissections for estimation of sporozoite rates were only carried out on their exophilous populations, and in both species these were shown to contribute to malaria transmission. Attention was concentrated on dissecting the other Anophelines, special attention being paid to A. nili. Only two species were found with infected salivary glands. A. flavicosta had a crude sporozoite rate of 2·74 per cent, of the 73 dissected, and from 998 examples of A. nili a crude sporozoite rate of 0·80 per cent, was obtained. It was thought that as A. flavicosta was mainly zoophilous it was possible that the sporozoites in the glands were of malaria not of human origin. It appeared that where A. nili was common it could become a secondary vector, and on account of its marked exophilic nature it might prove difficult to interrupt transmisssion by this species.

The relatively recent increase in towns of C. p. fatigans and the almost virtual disappearance of C. nebulosus Theo., formerly the predominant Culicine, and the possibility that this change might have been initiated by the practice in recent years of using DDT larvicidal formulations and not oil, is discussed.

A method is described whereby tsetse visiting a stationary ox can be observed through a one-way glass screen in the presence or absence of man. Under the latter condition six times as many adults of Glossina pallidipes Aust. perch and feed on the ox. In G. morsitans Westw. most flies land in the head-down position and are unaffected by man's presence, but in the absence of man there is a four-fold increase in the number which land and feed in the head-up position. Calculations indicate that in the absence of man virtually all G. pallidipes adults attracted to the ox alight on it, and nearly all attempt to feed. Man's presence not only repels many tsetse completely but also inhibits the landing response of many of those that do approach the ox.

Recognition of Orthoptera species by means of their song is widely used in field work but requires expertise. It is now possible to develop computer-based systems to achieve the same task with a number of advantages including continuous long term unattended operation and automatic species logging. The system described here achieves automated discrimination between different species by utilizing a novel time domain signal coding technique and an artificial neural network. The system has previously been shown to recognize 25 species of British Orthoptera with 99% accuracy for good quality sounds. This paper tests the system on field recordings of four species of grasshopper in northern England in 2002 and shows that it is capable of not only correctly recognizing the target species under a range of acoustic conditions but also of recognizing other sounds such as birds and man-made sounds. Recognition accuracies for the four species of typically 70–100% are obtained for field recordings with varying sound intensities and background signals.