The biting habits of Simulium austeni Edwards, a species widely distributed through Europe and European Russia, were investigated in a population of flies creating a medical problem along the Stour Valley, Dorset, England, in May each year. Surveys were made by questionnaires and ‘bite-recording forms’. Sweep-netting, suction-trapping and sticky-trapping of adult flies was carried out. A search was made for oviposition sites. After initial complaints in the early 1960s, the problem reached a peak between 1969 and 1971 and has since shown an apparent decline. Women suffered more than men, with most bites received on the lower limbs. Biting activity was greatest between 09.00 and 21.00 h, and flight activity was greatest in the afternoon. Extensive male swarms were associated with mating and smaller female swarms with blood-sucking. Mating probably precedes biting. The absence of eggs from surface vegetation or stones and their widespread occurrence in the sediment, suggest that oviposition takes places directly into the water.

An experimental hut trial of bednets was undertaken in The Gambia to compare six different permethrin treatments, including a wash-resistant formulation, and to test the effect of thorough hand washing of the nets. The wash-resistant formulation on nylon and cotton nets deterred Anopheles gambiae Giles (sensu lato) from house entry. All treated bednets killed a significantly higher number of A. gambiae (sensu lato) than untreated nets. The ability to kill mosquitoes was not diminished with the wash-resistant and Wellcome formulations after washing unlike the normal ICI formulation, this result being consistent with the permethrin residues found by gas liquid chromatographic (GLC) analyses to persist on the nets after washing. The mortality on treated cotton nets was significantly less than on treated nylon nets. Of the unwashed nets only the cotton net was significantly repellent. Both washed and unwashed treated nets significantly reduced the proportion of human bloodfed mosquitoes that survived and were potentially able to transmit malaria. Although the wash-resistant formulation might prove more efficient at killing mosquitoes with time, as compared to the other treatments, in The Gambia, where women wash their nets frequently, we suggest that the cheapest and most readily available formulation is used on nylon nets where possible.

An account is given of laboratory studies and field observations in Jamaica and British Honduras on the host-plants, life-history and habits of Saccharosydne saccharivora (Westw.), a major pest of sugar-cane. The original host-plants of S. saccharivora are shown to be two species of grasses, Andropogon glomeratus and A. bicornis. The immature stages of S. saccharivora are described and illustrated; the five nymphal instars may most easily be distinguished by their increasing size, the differentiation of the wing buds and the increasing spinosity of the metathoracic tibia and tarsus. Daily records of individuals of S. saccharivora show the duration of the different stages on fertilised plant cane at c. 80°F to be as follows: egg, 15–19 days; instar 1, 6–7 days; instars 2, 3 and 4, each 4–5 days; instar 5, 6–7 days; adult male, about one week; adult female, up to four weeks. The complete life-cycle took 6½–7 weeks, but was slower on unfertilised ratoon cane. In describing the habits of S. saccharivora, particular attention is given to feeding (feeding probes reach the bundle sheath cells and phloem of the lamina), oviposition (young leaves are the preferred oviposition site) and migration (immigration of adults on to young cane occurred at all times of year).

Field and laboratory studies on the water-velocity preferences of the larvae of Simulium monticola Fried, and S. variegatum (Mg.) show that both species occur in velocities of 0·5–2·5 m./sec. but aggregate in the velocity range 1·0–2·0 m./sec.

The velocity range that the larvae of different species of Simulium can withstand indicates that current speed plays an important part in governing the distribution of blackfly larvae, and perhaps isolating different species along watercourses.

The present study is based primarily on beetles collected in the field. Although several individuals of Capnodis carbonaria, Klug, and C. tenebrionis, were reared successfully from egg to maturity, these beetles were as a rule weak and short-lived, and consequently unsatisfactory for the purposes of this investigation.

The orchard bee species Osmia cornuta (Latreille) and O. rufa (Linnaeus) are both European in distribution. Osmia cornuta is distributed in the central and southern half of the continent, while O. rufa is distributed additionally in more northern parts of Europe, including Great Britain. These bees over-winter in cocoons as diapausing adults. The freezing temperatures of overwintering adults of O. cornuta and O. rufa during diapause are similar: −30°C to −24°C and −31°C to −26°C, respectively. However, there are differences in the termination of their diapause. Under natural conditions in the wider area of Belgrade, O. rufa appears in spring about two weeks later than O. cornuta.

The coexistence of closely related species is often hampered by resource competition or reproductive interference (interspecific sexual interactions). Species utilising similar signal channels might face substantial problems when they co-occur. It has, therefore, been suggested that reinforcement might drive signal evolution in narrow suture zones of secondary contact. However, species with large overlapping ranges are usually not believed to interact sexually. The Slender Ground-hopper, Tetrix subulata, and the Common Ground-hopper, Tetrix undulata (Orthoptera: Tetrigidae) are sister species, which occur sympatrically in large parts of western and Central Europe, but rarely share the same habitat. It has been hypothesized that reproductive interference might account for their missing coexistence. Here, we test experimentally whether these two species interact sexually. Our results suggest an incomplete premating isolation of these ground-hoppers, as we recorded heterospecific courtship, mating attempts and mating. The number of conspecific copulations and mating attempts of T. subulata decreased substantially in the presence of T. undulata, whereas the latter species was not negatively affected. Males of both species preferred to approach females of T. undulata, whereas females of both species did not discriminate against heterospecific males. Further studies on the reproductive success are needed to clarify whether reproductive interference might influence habitat partitioning between these species.

1. All the species of Siberian grasshoppers that have been studied in sufficient detail consist of a series of races exhibiting parallel coloration, structure and behaviour characters.

2. Every race of Chorthippus albomarginatus, Zett., Aeropus sibiricus, L., and of other species, has in its hopper and adult stage a series of colour forms analogous in their characters to the phases solitaria, transiens and gregaria of swarming locusts.

3. These colour forms are very unstable and undergo changes during the individual life due to the conditions of breeding.

4. Breeding in crowded conditions results in the predominance of dark-coloured forms, with black and sometimes with orange spots. Breeding in isolation, on the contrary, results in light forms of various colours.

5. No complete transformation of all the individuals in a population is observed in Siberian grasshoppers, and the intermediate forms represent a considerable portion of every population.

6. These colour forms, which can be considered as phases, differ also in their structural characters. Phase gregaria is larger and more long-winged than phase solitaria.

7. The phases differ further in their behaviour, ph. gregaria being more mobile and inclined to migrations, than ph. solitaria.

8. Every species and every race which have been studied exhibit a potential ability to produce phases, but this ability is not equal in all species and races. Those species and races which, owing to their habits and to the conditions of their habitats, can multiply in masses in restricted areas are more inclined to phase variability.

Mark–release–recapture experiments were undertaken in order to investigate the movement of adult Diabrotica virgifera virgifera LeConte from accidental introduction points towards suitable habitats, such as its host plant, Zea mays L. In Hungary in 2003 and 2004, nine mark–release–recapture experiments were carried out in a grass steppe area and lucerne field, in which two small maize fields (10 × 10 m) had been planted 300 m distant from the central release point. After each release of 5500 to 6000 marked D. v. virgifera, beetle recaptures were recorded three times using non-baited yellow sticky traps placed on 30, 105, 205 and 305 m radii around the release point. In seven out of 15 recapture periods (47%), beetle populations showed no directional movements, and their movements towards any particular habitat cannot be predicted. During five recapture periods (33%), beetle populations showed a uni-directional movement, and in three cases (20%) a bi-directional movement was observed. In 10 out of 15 recapture periods (67%), the released populations moved in a direction that was comparable with the mean wind direction during these periods; thus, beetle movements were slightly correlated with wind direction. On average over sites and years, beetles were not preferentially moving towards the two small maize fields (located 300 m from the release point) compared to other directions. However, beetles moved significantly more frequently in the direction of naturally-occurring maize fields within a radius of 1500 m than towards other habitats. Beetles stayed more frequently within flowering lucerne fields out to a radius of 300 and 600 m than in non-flowering lucerne or other habitats. On average, 2.8% (SD 3.2) of all recaptured beetles arrived in one of the two small maize fields located 300 m from their release point indicating that there is a high risk of a founder population establishing. Habitat management cannot be suggested as a means of preventing the beetle's initial dispersal because movement was usually non-directional, and alternative food plants were used prior to reaching maize.

The developmental and reproductive biology of a new avocado pest, Scirtothrips perseae Nakahara, was determined in the laboratory at five constant temperatures, 15, 20, 25, 27.5 and 30°C. At 20°C, S. perseae exhibited greatest larval to adult survivorship (41%), and mated females produced a greater proportion of female offspring at this temperature when compared to 15, 25, 27.5 and 30°C. Average lifetime fecundity and preoviposition period was greatest at 15°C at 39.6 eggs per female and 17.6 days, respectively. Jackknifed estimates of net reproduction (Ro), capacity for increase (rc), intrinsic rate of increase (rm), and finite rate of increase (λ) were all significantly greater at 20°C than corresponding values at 15, 25 and 27.5°C. Population doubling time (Td) was significantly lower at 20°C, indicating S. perseae populations can double 33–71% faster at this temperature in comparison to 15, 25 and 27.5°C. Mean adult longevity decreased with increasing temperature, from a maximum of 52.4 days at 15°C to a minimum of 2.4 days at 30°C. Developmental rates increased linearly with increasing temperatures for eggs and rates were non-linear for development of first and second instar larvae, propupae, pupae, and for egg to adult development. Linear regression and fitting of the modified Logan model to developmental rate data for egg to adult development estimated that 344.8 day degrees were required above a minimum threshold of 6.9°C to complete development. An upper developmental threshold was estimated at 37.6°C with an optimal temperature of 30.5°C for egg to adult development. Unmated females produced only male offspring confirming arrhenotoky in S. perseae.

Cochliomyia hominivorax and Cochliomyia macellaria are endemic Neotropical Calliphoridae species. The former causes severe myiasis in hosts while the latter is Sarcosaprophagous, but commonly found as a second invader in wounds. Due to the morphological similarity between them and the potential losses that C. hominivorax represents for cattle breeders, the rapid and correct identification of these two species is very important. In addition to a correct identification of these species, a good knowledge of C. hominivorax biology can be helpful for designing control programs. We applied geometric morphometric methods to assess wing differences between C. hominivorax and C. macellaria and conduct a preliminary analysis of wing morphological variation in C. hominivorax populations. Canonical variate analysis, using wing shape data, correctly classified 100% of the individuals analyzed according to sex and species. This result demonstrates that wing morphometry is a simple and reliable method for identifying C. hominivorax and C. macellaria samples and can be used to monitor C. hominivorax. Both species show sexual dimorphism, but in C. hominivorax it is magnified. We suggest that this may reflect different histories of selection pressures operating on males and females. Significant differences in wing size and shape were obtained among C. hominivorax populations, with little correlation with latitude. This result suggests that wing variation is also a good morphological marker for studying population variation in C. hominivorax.

Aëdes (Stegomyia) variegatus (Dol.) is a widely-spread species in the Australasian region, and under its synonym of Stegomyia pseudoscutellaris is well-known as the carrier of filaria in Fiji and Polynesia in general. Up to the present the existence of definite local variations has not been suspected, partly because the species itself has been regarded as the Australasian representative of the Oriental A. albopictus (Skuse). Recently, however, Dr. P. A. Buxton has discovered that larvae from Samoa and the New Hebrides differ in a constant manner, and at his suggestion I have scrutinised the whole series of specimens of this species in the British Museum. This examination appears to show that there are at least five distinct varieties, distinguishable by small differences of colour and also by the male hypopygium, especially in the form of the basal lobe of the side-piece. The characters are fairly well defined, but are perhaps best treated as varietal rather than specific, especially as their significance appears to be mainly geographical.

Indirect and direct measures of parasitoid activity were taken in grassland and autumn-sown cereals in southern England between 1979 and 1981. Studies of anholocyclic aphid populations in the winter months were followed through to parasitism of the main pest species, Sitobion avenae (F.), during the period of population increase in April and May. Aphidius spp. parasitized artificially-established colonies of cereal aphids in ryegrass in every month between December and May of both seasons, but there was no Aphidius activity until March-April in winter cereals sown early enough to receive an autumn input of aphids and parasitoids, apparently due to the small amount of physiological time that accumulates before temperatures drop in the winter months. A. rhopalosiphi De Stefani Perez and A. picipes (Nees) were completely dominant over other parasitoid species in the winter and spring period. Natural populations of Aphidius adults and parasitized aphids were low (<2/m2) in both winters, and percentage parasitism of S. avenae measured by dissection in March and April did not exceed 11·7%. Rates of S. avenae parasitism in many winter wheat fields peaked in May, before the peak and rapid decline in aphid populations. The significance of winter and spring parasitoid activity to the survival of the parasitoid and effects on pest aphid peaks are discussed.

Previous studies have shown the sandfly Lutzomyia evansi to be the vector of Leishmania chagasi in northern Colombia. A longitudinal survey during seven months on the host preference of Lutzomyia evansi was conducted in the visceral leishmaniasis focus of San Andrés de Sotavento, Colombia. Host preference was determined by presenting sandflies with a choice of three baits (human, and the reservoirs dog and opossum) and a blank control in specially designed cone traps. A rotational experimental design involved 56 trap nights in which the effect of bait, proximity to forest and season could be distinguished from the potentially confounding factors of site and day to day variation. From a total of 598 sandflies caught during all experiments, females and males of Lutzomyia evansi accounted for 93.8% of the captures in the baited traps. Overall, human attracted the greatest number of sand flies, followed by the other two baits. Attraction and feeding success showed significant differences (P < 0.0001) between baits.

A description is given of Ukara Island, which lies in the Tanganyika part of Lake Victoria, with an annotated list of mosquitos and other arthropods of medical importance found there. There are also notes on local plants and vertebrates.

The inhabitants, called Bakara, live in cone-shaped grass huts over 20 ft. in height and diameter. People and cattle are housed together.

The area of the island is about 45 sq. miles. The 17,000 inhabitants, almost entirely African, support themselves by advanced agricultural practices involving the use of manure and nitrogenous plants. There is a coastal belt of intense cultivation and a large central area of uninhabited grassland with extensive deep erosion. The beds of rivers which radiate from the centre are occupied by large irrigated areas. Seasonal fluctuations in lake level have little effect in general on cropping practices which are affected more by seasonal variations in rainfall.

The average rainfall for 1950–52 was 62 inches per annum. Temperatures are equable throughout the year. Mean maxima for 1953 were 81°F. for April, 83°F. for May, 82°F. for June and 81°F. for July—mean minima were 70°F. for April, 68°F. for May, 69°F. for June and 67°F. for July. Wind velocities, recorded at noon, vary between 4·8 metres per second in June and 2·4 in January.

Semiochemical-based pest management programs have been increasingly used to provide environmentally friendly methods for the control of major insect pests. The efficacy of the mating disruption technique has been demonstrated for several moth pests. Unfortunately, not many experiments on mating disruption to control diaspididae species have been documented. In this work, biodegradable dispensers for mating disruption with increasing pheromone loads were used in order to study the potential of this technique for the control of Aonidiella aurantii Maskell. Field trial results demonstrated that dispensers loaded with 50 mg (a.i.) (20 g ha−1) and 100 mg (a.i.) (40 g ha−1) of sex pheromone were the most suitable, achieving significant reductions in male catches, compared to an untreated plot. In treated plots, virtually a 70% reduction in damage to fruit was recorded. Pheromone release profiles of all the dispensers were also studied under field conditions. We found that emission values >250 μg day−1 were the most suitable. This study suggests a new biodegradable dispenser capable of interfering with normal A. aurantii chemical communication. The use of mating disruption as a control method against A. aurantii is discussed.

The whitefly Bemisia tabaci is a pest vector of begomoviruses on crops worldwide. Bemisia tabaci is composed of a complex of cryptic species which barely interbreed. An exception is the Ms from the South West Indian Ocean (SWIO), which crosses in low proportions with the exotic B. The Ms, together with B and Q is part of the same phylogenetic clad. To infer the genetic structure, the geographical range and putative origin of this putative species, microsatellite data and mitochondrial DNA (cytochrome oxydase I) sequences were analysed on an extensive sample set, including all the islands of the region and samples from mainland Africa. Only B and Ms populations were detected across these islands. The exotic B was found only on the islands of Réunion and Mauritius, whereas the Ms is found on all the SWIO islands. Very high isolation by distance was found for the Ms populations between islands of the SWIO, suggesting a long period of presence in this region. Ms populations from mainland Africa had a higher COI diversity than the Ms of the SWIO islands. This diversity is correlated with size and geological ages of the SWIO islands. The population genetic data obtained are in accordance with an origin of Ms in Africa, followed by its expansion and evolution across the SWIO islands prior to human arrival, confirming the status of Ms as indigenous in the SWIO islands.

Five species of Muscidae were found to be commonly associated with dairy heifers in three areas in southern England. The biting flies Haematobosca stimulans (Mg.) and Stomoxys calcitrans (L.) were relatively rare and fed from the back, flanks and legs. The horn fly, Haematobia irritans (L.), was present in highest numbers; it rested on the back and fed on the legs, belly and occasionally on the teats. Musca autumnalis Deg. was found mainly on the head and had a restricted season. Hydrotaea irritans (Fall.) had a marked diurnal variation in activity, being most abundant in the morning and evening. It was found on the head but predominantly on the belly and teats. When judged by its site preference on cattle, it is the fly most likely to be involved in the transmission of summer mastitis.

The developmental rates and fecundity of two important African maize pests, Sesamia calamistis Hampson and Eldana saccharina Walker, were studied under constant temperatures and with two larval diets. Five temperatures (15°, 20°, 25°, 30° and 35°C) were used to investigate developmental rates and three temperatures (20°, 25° and 30°C) were used in fecundity experiments. Larvae were reared on maize stem cuttings and on artificial diet. The developmental period for S. calamistis on artificial diet required over 700 degree-days (DD); eggs needed 122 DD above a threshold of 9.7°, larvae required 383 DD above 12.2°C and pupae 204 DD above 10.2°C. The developmental period for E. saccharina on artificial diet was 665 DD; eggs required 125 DD above 9.1°C, larvae 400 DD above 10.6°C and pupae 140 DD above 8.8°C. On artificial diet both species developed faster and had higher threshold temperatures for larval development than when reared on maize stem cuttings. Pupal development rates did not differ between artificial diet and maize stem for either species, although developmental thresholds were marginally lower on artificial diet. S. calamistis averaged 250–690 eggs/female although some individuals produced more than 1000 eggs. Adult females lived 5.7 days at 30°C and 10 days at 20°C. E. saccharina females produce more eggs and lived longer than S. calamistis females. Average fecundity for E. saccharina was 470–620 eggs/female, but several individuals produced more than 1200 eggs. Adult females lived 6.6 days at 30°C and 14.6 days at 20°C.

Spatial distribution studies in pest management identify the locations where pest attacks on crops are most severe, enabling us to understand and predict the movement of such pests. Studies on the spatial distribution of two mite species, however, are rather scarce. The mites Polyphagotarsonemus latus and Tetranychus bastosi are the major pests affecting physic nut plantations (Jatropha curcas). Therefore, the objective of this study was to measure the spatial distributions of P. latus and T. bastosi in the physic nut plantations. Mite densities were monitored over 2 years in two different plantations. Sample locations were georeferenced. The experimental data were analyzed using geostatistical analyses. The total mite density was found to be higher when only one species was present (T. bastosi). When both the mite species were found in the same plantation, their peak densities occurred at different times. These mites, however, exhibited uniform spatial distribution when found at extreme densities (low or high). However, the mites showed an aggregated distribution in intermediate densities. Mite spatial distribution models were isotropic. Mite colonization commenced at the periphery of the areas under study, whereas the high-density patches extended until they reached 30 m in diameter. This has not been reported for J. curcas plants before.