Distances moved by Cicadulina spp. were investigated at Salisbury, Rhodesia, during 1968–69, by using small plots of oats to trap adults dispersing from populations breeding in Pennisetum clandestinum or Eleusine indica grasses. The shape of the curves constructed for fall of numbers with distance confirmed laboratory findings that populations are composed of long and short distance fliers. The curve for numbers of infective Cicadulina punctures estimated from the gradient of maize streak infection falling from adjoining cereals was also of similar shape. Mean flight times indicated that a steep fall for about 10 m from source is due largely to short distance fliers making trivial movements, and the subsequent gentle fall is due to long distance fliers which may disperse many kilometres depending on the wind speed. There were higher proportions of long distance fliers amongst C. mbila (Naudé) compared to C. storeyi China, and amongst females compared to males dispersing downwind. A predominance of long distance fliers dispersing from drying grasses during April–September, and of short distance fliers present in irrigated grasses and cereals during October–March, causes seasonal differences in the patterns of maize streak infection and in the effectiveness of barriers of clear ground as a preventive measure.

The Argentine stem weevil (Listronotus bonariensis) was an economically important pest in New Zealand pastures until the release of the parasitoid Microctonus hyperodae. This contribution uses historical data to investigate the regulation of the pest populations prior to, and somewhat during, the establishment of this parasitoid in dryland Canterbury, New Zealand. Thus, a significant goal of this study is to provide an L. bonariensis population dynamics baseline for any future work that aims to analyse the full effects of M. hyperodae on the weevil, now that equilibrium with the weevil host has been reached.

The population dynamics of L. bonariensis, based on a life-table approach, were investigated using data collected regularly for eight years from populations in Canterbury, New Zealand. The key factor affecting end-of-season L. bonariensis density was found to be variation in second generation fourth instar prepupal and pupal mortality. This may have been caused by arrested development and ongoing mortality resulting from the onset of cooler autumnal conditions.

A compensatory response was found in recruitment to the second summer weevil generation, whereby the realised fecundity of the emergent first summer generation of weevils was found to be negatively related to the density of adult weevils per ryegrass tiller. This is the first time that this has been found via long-term population analysis of L. bonariensis, although indications of this have been found elsewhere in caging, pot and small plot experiments.

In this study, the effect of the parasitoid biocontrol agent Microctonus hyperodae on L. bonariensis population dynamics was unclear, as the analysis covered a period when the parasitoid Microctonus hyperodae was introduced and still establishing. It does, however, raise important questions for future analysis in terms of the interaction between parasitism and unrealised fecundity.

The results in this contribution also highlighted regional differences. Overwintering mortality of adult weevils in Canterbury was constant between years, whilst earlier studies in the North Island Waikato region indicated this mortality was density dependent. In addition, the availability of tillers in endophyte-free ryegrass pastures in Canterbury had no influence on egg and early-instar larval survival, which contrasts with the finding from endophytic Waikato pastures.

The best method of assessing the wetting powers of liquids is to measure the contact angle formed with a particular solid surface. In order to study the wetting of insects by spray liquids, it was necessary to measure, as rapidly as possible, the contact angles of very small droplets on restricted surfaces (such as portions of the insects). The apparatus used projected a greatly enlarged image of the drop, the outline of which could be traced very quickly and used for subsequent calculations.

Under practical conditions, spray droplets impact on insects with some relative velocity either due to drift of the spray particles or to flight movements of the insect.Measurements were therefore made of the contact angles formed by droplets of water of known size falling on to insects (or to a beeswax surface) at a known speed. It was found that with rather large drops (5 mm. diameter) the contact angles formed were somewhat lower than the normal advancing contact angle. With small droplets (0·1-0·5 mm. diameter) there was no difference. Biological tests were made with 30 species of insects, differing widely in the nature of their integument and habitat. The resistance to wetting was found to vary greatly, not only from species to species but also on different parts of the body of a single insect. In general, most of the insects were readily wetted by oils and unwetted by water. Insects withhard cuticular lipoids, such as Tenebrio, were more hydrophobic than the Blattidswith greasy cuticular waxes. A few species were both lipophilic and hydrophilic (larvae of Mamestra, Polia, Musca). Apart from the chemical nature of the cuticle, irregularities and the presence or absence of hairs were important. Increased roughnesslowers the contact angles of liquids with good wetting powers, but has the opposite effect with liquids with poor wetting powers. Measurements were made of thecontact angles formed on individual hairs of Arctia caja larvae by spray droplets. The contact angles formed on these hairs by plain liquids were strongly correlated with the angles formed on smooth Tenebrio cuticle or on an artificial beeswax surface; but there was only very rough correlation between the three sets of data when aqueous solutions of wetting agents were tested.

The test liquids included saturated and unsaturated hydrocarbons, mineral oils with varying aromatic contents, organic esters, alcohols and aqueous solutions. Among the hydrocarbons, members of the aliphatic series wet insect cuticle more readily than the aromatic group. The aromatic contents of the oils did not, however, affect their very high wetting powers.

The effects of adding surface active agents to aqueous sprays were investigated. Of the samples tested, the most effective wetting agents were those with neutral un-ionised molecules.

A population of Glossina swynnertoni Aust., at Shinyanga, Tanganyika, has been studied in respect of size and fat content of non-teneral males by monthly samples over a period of 13 years.

Flies are large from February to July and small from August to January, and this change in size suggests an effect of the wet season (December to May) and dry season (June to November) upon the parent females, allowing for the time-lag of two months representing pupal development and mean age of adult males at capture. Male flies have more fat in the rains and less in the dry season and it is possible that similar changes in the nutritional status of females are responsible for the observed size changes.

The correlation found in earlier work between the size of male flies in any month and saturation deficit two months earlier is confirmed, but reasons are given for rejecting a simple causal interpretation of this correlation.

Since 1951, there has been a progressive decrease in size of G. swynnertoni in the area studied, more especially as regards those produced in the dry season.

In the summer of 1958, experiments were conducted in the vicinity of Brunston Muir, Midlothian, 11 miles SE. of Edinburgh, to measure the flight range of Culicoides impunctatus Goetgh. from its breeding site in the direction of the prevailing south-westerly wind. Thirty-six sticky traps were exposed for six weeks from 27th May to 7th July and captured 23,211 specimens of Culicoides, of which 20,105 were of C. impunctatus (7,207 males and 12,898 females).

Eleven of the traps were arranged in a line over 1,200 yd. The catch of females did not alter for 400 yd., then decreased to a new level which remained constant from 600 to 1,200 yd. This decrease was associated more with the absence of livestock after 550 yd. than with any density/distance regression. The male distribution was similar to that of the females.

Ten more traps stretched over 750 yd. and again no regression was discernible. The female distribution was affected more by the availability of hosts than distance from the breeding site. The male distribution here was different. They appeared to pass less readily through a gap in a narrow belt of woodland than did the females.

1. Owing to the history of yellow fever in the Sudan and the lines of communication which traverse the country, a general survey of the mosquitos, particularly the Culicines, is of practical interest. The known potential vectors of yellow fever are listed.

2. Observations on the man-biting or man-ignoring habits of some species are recorded and also notes on the bionomics of Taeniorhynchus africanus, T. uniformis, Aëdes aegypti and other species.

3. For purposes of description the country is divided into sub-divisions of the recognized faunal areas and notes are given on the Culicines of each.

4. Brief observations are made on mosquito control measures against yellow fever.

Local isolates of Bacillus thuringiensis were isolated from infected rice stemborers, soils, rice bran and rice mill dust. Of 83 isolates serotyped by B. thuringiensis H-antisera, 13 serotypes were identified. Those serotypes were assigned to B. thuringiensis of subspecies canadensis, galleriae, kenyae, kurstaki, neoleonensis, aizawai, alesti, entomocidus, tochigiensis and tolworthi. Three serotypes, 3a:3c:3d, 5a:5b/21 and 17/27, were unnamed and portend to be new subspecies. Morphological studies of delta-endotoxin or crystal protein of each subspecies showed significant differences in size and shape. Bipyramidal crystals, spherical and cuboidal crystals and the combinations of these structures were observed. Toxicity of sporulated cultures and isolated crystal proteins of B. thuringiensis strains to five species of economically important insects were determined using diet incorporation bioassays. Extracted crystal proteins from certain B. thuringiensis subspecies were highly toxic to some insect species. These have the potential of providing alternative strategies for utilizing B. thuringiensis for controlling insects.

Cuticular hydrocarbons were analysed by gas chromatography (GC) in 564 specimens of the Anopheles gambiae Giles complex from several West African sites, to determine whether individual A. gambiae sensu stricto and A. arabiensis Patton can be reliably identified, and to investigate the extent to which distinct chromosomal forms of A. gambiae sensu stricto, which are ecologically restricted as well as in some cases sexually isolated, can be distinguished by their cuticular hydrocarbons. Sympatric A. arabiensis and A. gambiae sensu stricto at Banambani, Mali could be distinguished with 90% correct identifications using the concentrations of four hydrocarbons in a linear discriminant function, but at a second site in Moribabougou, Mali, A. arabiensis was indistinguishable from a small sample of Bamako form of A. gambiae sensu stricto. Sympatric chromosomal forms of A. gambiae sensu stricto could be separated and clearest differences were found between the Mopti and Bamako forms. Direct gene flow between these forms has been found to be completely lacking despite partial intergradation of each form with the savanna form. Ethological isolating mechanisms between these forms have not however been demonstrated. Estimates of the rates of misclassification between the savanna form and the Mopti and Bamko forms reflect the degree of integradation observed amongst these forms by analysis of karyotype frequency in the wild. Discrimination was poor when an allopatric sample of the Mopti form was compared with other samples. An overall test shows that the proportion of correct classifications in discriminant analysis tends to be higher between sympatric than between allopatric populations; however, more extensive sampling would be needed for a rigorous test. The involvement of cuticular hydrocarbons in specific mate recognition systems is discussed.

In Leptohylemyia coarctata (Fall.) the germarium cuts off oocytes which develop through the stages 00 and 0 and I-V, recognised in other Cyclorraphous flies, in 4–5 weeks. All eggs of one batch of the gonadotrophic cycle ripen at the same time. After oviposition, the split intima, the remains of the follicular epithelium, and the nurse cells slowly contract to form the follicular relic. Flies swept from winter wheat during June and July and caught in water traps in July and August showed all stages of egg development. In 1970, 24·7% of the females swept from the crop had completed the first, 4–7% the second and 0–4% the third gonadotrophic cycle. All the eggs were not laid at the same time. During later gonadotrophic cycles, some ovarioles were non-functional. Flies laid one or two batches of eggs, rarely three. In 1970, many flies were attacked and killed by E. muscae. Only one out of 115 newly emerged female wheat bulb flies presented with foods usually found in the crop or citrated blood contained mature eggs after 24–27 days in small cages. Those fed only on 0·1 M glucose survived but did not deposit yolk in the ovum; those provided only with yeast paste died. Honey dew from cereal aphids was the main source of sugar. Water in droplet form and space to move seem necessary for the maturation of the eggs.

During ultra-low-volume aerial applications of endosulfan at 14 g/ha for control of Glossina morsitans morsitans Westw. and G. pallidipes Aust. in savanna woodland in Zimbabwe-Rhodesia, the effects on other organisms were monitored. The numbers and varieties of arthropods, mainly insects, were studied by catches in light-straps and open trays. Mortalities amongst exposed aquatic insects, fish, frogs, mice and stingless bees (Trigona spp.) were noted. No deleterious effect of the insecticide was demonstrated, Other than on fish (Tilapia spp.) in shallow water.

Carabid inventories gained via pitfall trapping were compared to manual samples from light towers. A comparison of the two methods indicated that pitfall traps recorded a significantly higher diversity of carabids and were efficient in indicating changes of habitat conditions. Nevertheless, this method failed to give near-complete inventories of all carabid species present. Manual sampling at light towers resulted in far greater sample sizes, and this method was particularly efficient in monitoring potential pest species, but again failed to record all species present. Both methods hence showed different strengths, and only a combination, potentially also including further sampling techniques, will enable the generation of complete species inventories.

An account is given of seasonal changes in the incidence and relative abundance of a number of Phlebotomine sandflies which rest in termite hills in two widely separated areas of Kenya.

The annual pattern of rainfall distribution is shown to be of greater importance than the total precipitation in influencing the gross distribution and local abundance of many sandflies.

Kenya sandflies fall readily into ‘ perennial ’ and ‘ rainy-season ’ groups: the former have a wide distribution and appear to breed throughout the year. The distribution of the ‘ rainy-season ’ sandflies is relatively restricted, since these species are found almost exclusively in areas with a bimodal pattern of annual rainfall; it is suggested that they may survive the intervening dry periods in larval diapause. The length rather than the severity of the dry seasons is thought to be the limiting factor in the distribution of ‘ rainy-season ’ species.

Examples are given of the seasonal changes in structure of populations made up of several species sharing, in the adult form, the same termite-hill habitat.

Flat grain beetles of the genus Cryptolestes (Coleoptera: Laemophloeidae) are one of the economically most important stored-product pests which feed on many kinds of agricultural products, especially grains. Nine of more than 40 described Cryptolestes species are recognized as stored-product pests and two of the pest species have a cosmopolitan distribution. Given the rapid growth in global trade of food products, ecological barriers to the spread of pests are easily overcome. Therefore, development of reliable systems for routine quarantine inspection and early infestation detection is vital. In the present study, we established a new rapid and accurate cytochrome c oxidase subunit I-based system for molecular identification of five common stored-product Cryptolestes species, namely, Cryptolestes capensis, Cryptolestes ferrugineus, Cryptolestes pusilloides, Cryptolestes pusillus and Cryptolestes turcicus. Five species-specific primer pairs for traditional uniplex polymerase chain reaction assay are described and their specificity and sensitivity for the identification process is evaluated using larval samples of 12 different populations from three continents (Asia, Europe and North America).

Previous work has shown that, under natural conditions in the Lake District, larvae of Phyllopertha horticola (L.) hatch in early July and feed actively on the roots of pasture plants during the next 3½–4 months, undergoing two moults. They then empty the gut and enter hibernation, pupating the following spring. Stores of organic material in grass roots are at their highest level during this autumn feeding period. It has also been shown that the egg production depends almost entirely on the weight of the hibernating larva or of the pupa, which thus plays an important part in determining the reproductive rate of the population, and studies were accordingly made on larval growth and certain factors affecting it.

Newly hatched larvae were cultured at 15°C. in moistened plaster-of-paris containers filled with a mixture of soil and germinating grass seeds. They moulted at about 20 and 45 days after hatching, and stopped feeding and entered hibernation at about 100 days. When the seeds were scattered on the soil surface, larval growth was slower. The mean larval weight, plotted against age, gave a sigmoid curve; in the. first instar and most of the second, the rate of increase in weight was proportional to the weight, but thereafter, up to the time of hibernation, it was more or less constant. The rate of growth of the individual larva was irregular, being slower at the moults and variable even in the middle of the instar.

Larvae cultured under semi-natural conditions in pots of growing grass in the open moulted about 3–4 and 7–9 weeks after hatching and entered hibernation at 100–120 days. Growth is possible on a wide variety of food plants, larvae cultured on 13 species of pasture plants grown in pure stands surviving to the hibernation stage on all but two of them.

During hibernation, the larva loses 20–25 per cent, of its weight, mostly in the first few weeks. The pupal weight is almost constant and does not appear to be affected by the temperature treatment of the hibernating larva. It is thus a useful index of effective larval growth.

The mean and (in brackets) range of the weights of all pupae collected in two fields in the Lake District between 1950 and 1953 were 139·3 mg. (65–242) for males and 171·3 mg. (72–310) for females. Field samples of hibernating larvae and of pupae show considerable variation in weight from place to place, from year to year and within apparently homogeneous areas.

Variation in the time at which larval growth takes place is a major cause of variation in pupal weight. The growth period of larvae in a field at Buttermere was three weeks earlier in 1952 than in 1950, though of the same duration, and the resulting pupae in 1953 were heavier than those in 1951. Two lots of larvae of similar parentage, grown in adjacent plots of grass out of doors, one of which both hatched and entered hibernation three weeks before the other, likewise showed a difference in weight at hibernation, the earlier lot being the heavier. A series of weighed samples of larvae taken from part of a field at Ambleside in 1953 at weekly intervals during the period when they were entering hibernation showed that heavier individuals did so before lighter ones, and males before females. Factors inducing mortality during this period thus operate selectively against females, because these are exposed to them for longer.

Field-collected larvae fed in the third instar on roots of lettuce produced pupae the following spring that were significantly heavier than those from larvae fed on roots of either ryegrass or clover.

There is no evidence to show that population density affects the weight of the hibernating larva or the pupa. On the other hand, larvae from soil from which the damaged turf had been stripped by birds were significantly lighter than those from the surrounding undisturbed sward.

When moving through the soil, larvae may meet and fatally injure each other by an undirected “ snapping ” reaction. This mechanism may limit population density. In an experiment in which larvae were reared in loose soil on grass roots, the mortality rate was seen to increase with the size and activity of the larvae, and also with the larval density.

In 1988/89 the nature and degree of hyperparasitism in two newly introduced parasitoids of exotic mealybug plant pests were examined in Togo. Associated with Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) (cassava mealybug) five indigenous hymenopterous hyperparasitoids were found adapted to the primary parasitoid Epidinocarsis lopezi (De Santis): Chartocerus sp. A (Signiphoridae), Prochiloneurus insolitus (Alam), P. aegyptiacus (Mercet) (Encyrtidae), Tetrastichus sp. (Eulophidae), and Marietta leopardina Motschulsky (Aphelinidae). The rate of hyperparasitism varied considerably (20–90%). At one sampling site Chartocerus sp. A was most frequent (52%), at the other site P. insolitus was found to dominate (55%). The same hyperparasitoids were associated with Rastrococcus invadens Williams (Hemiptera: Pseudococcidae), but with an additional Chartocerus (sp. B). Hyperparasitism ranged from 56 to 86%, with Chartocerus sp. A being the most important species. Multiple parasitism was observed on several occasions. In spite of generally high hyperparasitism, no detrimental effect on the control efficiency of either primary parasitoid was noticed.

Aëdes leucocelaenus transmits yellow fever virus readily in the laboratory and has twice been found infected in nature.

Except in south Brazil this species is much less common than Haemagogus spegazzinii among day-biting sylvan mosquitos captured with human bait.

A. leucocelaenus has a wide distribution throughout the forested area of this country.

As a natural vector of jungle yellow fever in the northern part of Brazil it is of secondary importance when compared to H. spegazzinii.

From 1986 to 1989, the factors that determined the abundance of Metopolophium dirhodum (Walker) on cereals were studied in western Czechoslovakia. Forty seven sites were selected within cereal fields, mainly of winter wheat. Host plant size and leaf area varied between sites. The maximum abundance of M. dirhodum per tiller varied annually and with host plant stature. The main factor determining maximum abundance was the length of time for which the aphid population grew. M. dirhodum populations differed both in the time of the onset and termination of their growth. On stunted plants population growth started, with little variation, 200 day degrees later than on well developed plants. Within years, nearly all populations ceased growing simultaneously. In years of low or medium aphid abundance it was 40 to 90 day degrees earlier than in aphid outbreak years, and this extension of the population growth was the principal cause of the outbreak. Population growth rates varied slightly with plant quality and differed little between years. They were not important factors determining maximum abundances. 55–75% of the aphids occupied the flag leaves. The lower leaves of well developed plants were more heavily populated than nutritionally and water stressed smaller plants. The population growth rates on particular leaves were related to leaf nitrogen content, but not water content. A relationship for calculating the maximum abundances from a census made during the middle phase of population growth was proposed.

Two novel full-length P450 cDNAs, CYP6CS1 and CYP6CW1, were cloned from the fourth instar nymphs of brown planthopper Nilaparvata lugens Stål (Hemiptera: Delphacidae) reared on its susceptible rice variety Taichung Native 1 (TN1) plants. The deduced proteins are typical microsomal P450s sharing conserved structural and functional domains with other insect CYP6 members. Temporal expression analysis by northern blot hybridization indicated pre-exposure to N. lugens moderately resistant rice Minghui 63 (MH63) seedlings caused a time course-dependent induction of CYP6CS1 which peaked after 24 h of treatment; in contrast, CYP6CW1 was induced and remained at a constant time course from 0–72 h. CYP6CS1 and CYP6CW1 are dramatically induced in gut tissues and, slightly upregulated in carcass and fat bodies as revealed in spatial gene expression analysis. Whole mount in situ hybridizaion revealed that the two genes are expressed at a basal level in gut tissue and Malpighian tubules in nymphs fed with TN1 rice. After exposure to MH63, the expression of CYP6CW1 was found to be high in the whole gut, including Malpighian tubules. Expression of CYP6CS1 was significantly increased in midgut, and slightly increased in foregut, hindgut and Malpighian tubules. These data suggest a potential role of the two P450s in determining patterns of N. lugens-rice relationships through allelochemical detoxification.

Arion vulgaris Moquin-Tandon 1855 is one of the most important invasive species in Europe, affecting both biodiversity and agriculture. The species is spreading in many parts of Europe, inflicting severe damage to horticultural plants and cultivated crops partly due to a lack of satisfactory and effective management solutions. Molluscicides have traditionally been used to manage slug densities, although the effects are variable and some have severe side-effects on other biota. Thus, there is a need to explore potential alternatives such as biological control. The nematode Phasmarhabditis hermaphrodita is the only biological agent that has been applied commercially so far. However, other biological control agents such as carabid beetles have also been found to be promising. In addition, some carabid species have been shown to feed on A. vulgaris in the field as well as in the laboratory. Two species in particular have been found to be important predators of A. vulgaris, and these species are also common in agricultural environments: Pterostichus melanarius and Carabus nemoralis. This study is the first to use semi-field experiments in a strawberry field, manipulating densities, to investigate how P. melanarius and C. nemoralis affect densities of A. vulgaris eggs and juveniles, respectively. Gut contents of C. nemoralis were analysed using multiplex PCR methods to detect DNA of juvenile slugs. Results show that both P. melanarius and C. nemoralis significantly affect densities of slug eggs and juvenile slugs under semi-field conditions and that C. nemoralis seems to prefer slugs smaller than one gram. Carabus nemoralis seems to be especially promising in reducing densities of A. vulgaris, and future studies should investigate the potential of using this species as a biological control agent.

The olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a key-pest in the main olives producing areas worldwide, and displays distinct preference to different olive cultivars. The present work intended to study oviposition preference towards three Portuguese cultivars (Cobrançosa, Madural, and Verdeal Transmontana) at different maturation indexes. Multiple oviposition bioassays (multiple-choice and no-choice) were conducted to assess cultivar preference. No-choice bioassays were conducted to assess the influence of different maturation indexes (MI 2; MI 3, and MI 4) in single cultivars. The longevity of olive fly adults according to the cultivar in which its larvae developed was also evaluated through survival assays.

Cultivar and maturation are crucial aspects in olive fly preference. Field and laboratory assays revealed a preference towards cv. Verdeal Transmontana olives and a lower susceptibility to cv. Cobrançosa olives. A higher preference was observed for olives at MI 2 and MI 3. The slower maturation process in cv. Verdeal Transmontana (still green while the other cultivars are reddish or at black stage) seems to have an attractive effect on olive fly females, thus increasing its infestation levels. Olive fly adults from both sexes live longer if emerged from pupae developed from cv. Verdeal Transmontana fruits and live less if emerged from cv. Cobrançosa. Therefore, olive cultivar and maturation process are crucial aspects in olive fly preference, also influencing the longevity of adults.