Felled logs of twelve species of Eucalyptus were exposed simultaneously to attack by Phoracantha semipunctata (F.) in Malawi. Colonisation was assessed by counting the number of larval feeding channels on the surface of the sapwood. The level of colonisation varied significantly between different tree species. E. fastigata and E. paniculata were much more heavily colonised than any of the other species. Possible factors contributing to this variation in susceptibility are discussed. The more susceptible species should be the most efficient for control operations involving the use of trap trees.

A chemical sex attractant for the male grass grub beetle (Costelytra zealandica (White)) has been shown to be present in a commercially available adhesive preparation.

The effect of temperature on the reproduction and development of Busseola fusca was studied under laboratory conditions. Single male–female pairs were confined to oviposition chambers kept at 15, 20, 26 and 30 ± 1°C and a 14L:10D photoperiod. Data on reproduction parameters were captured daily. Oviposition occurred at all the mentioned temperatures but no fertility was recorded at 30°C. The total number of eggs laid per female moth was between 300 and 400 and the optimum temperature for oviposition and fertility was between 20 and 26°C. Larval development was studied at five different temperature regimes, i.e. 15, 18, 20, 26 and 30 ± 1°C and a 14L:10D photoperiod. The most favourable temperature as well as the upper threshold temperature for larval development was between 26 and 30°C. Total development period was 152.6–52.6 days, respectively, at 15°C, and 26–30°C. The thermal constants for B. fusca was 99.50, 536.48, 246.25 and 893.66°D and lower temperature thresholds were 10.36, 8.14, 8.99 and 8.84°C, for completion of the egg, larval, pupal and egg-to-adult stages, respectively. Results on the thermal constants and lower and upper threshold temperatures of B. fusca can be used to predict the impact of climate change on the distribution and population growth of this pest.

In cyclical parthenogens, clonal diversity is expected to decrease due to selection and drift during the asexual phase per number of asexual generations. The decrease in diversity may be counteracted by immigration of new genotypes. We analysed temporal variation in clonal diversity in colonies of the monophagous tansy aphid, Macrosiphoniella tanacetaria (Kaltenbach), sampled four times over the course of a growing season. In a related field study, we recorded aphid colony sizes and the occurrence of winged dispersers throughout the season. The number of colonies increased from April, when asexual stem mothers hatched from the sexually produced eggs, to the end of June. The proportion of colonies with winged individuals also increased over this period. After a severe reduction in colony sizes in late summer, a second expansion phase occurred in October when sexuals were produced. At the season's end, the only winged forms were males. A linked genetic study showed that the number of microsatellite multilocus genotypes and genetic variability assessed at three polymorphic loci per colony decreased from June to October. Overall, the relatedness of wingless to winged individuals within colonies was lower than average relatedness among wingless individuals, suggesting that winged forms mainly originated in different colonies. The results demonstrate that patterns of genetic diversity within colonies can be explained by the antagonistic forces of clonal selection, migration and genetic drift (largely due to midsummer population bottlenecks). We further suggest that the males emigrate over comparatively longer distances than winged asexual females.

The content of proline, alanine and glutamate in the thorax of tsetse flies (Glossina morsitans Westw.) caught by two different sampling techniques is compared. Flies caught on a stationary bait animal have significantly less proline and significantly more alanine and glutamate than flies caught on a fly-round. The difference suggests that flies of the bait sample have been more active than flies of the fly-round sample during the period immediately preceding capture.

The hypothesis that spring emergence of the pea moth Cydia nigricana is regulated by environmental factors, particularly photoperiod and temperature, was examined in this study. A long-term field study was conducted in two distinct pea-growing areas in Hesse and Saxony, Germany. Strong correlations between the flight phenology of pea moth in spring and air temperature, soil temperature, solar radiation and day length were demonstrated for three consecutive years. In laboratory experiments, we elucidated the interaction of different photoperiod-temperature regimes, verifying cumulative day-degree data in relation to pea moth emergence rates in the field. C. nigricana temperature sensitivity is apparently initiated by long day conditions with a critical day length of about 14 h L:D. The overall results contribute to the theory that photoperiod and temperature interact as regulatory cues for spring emergence of C. nigricana. The findings are discussed in terms of the development of predictive models and decision support systems for pea moth control.

The tachinid fly Drino inconspicuoides (Diptera: Tachinidae) is an ovolarviparous endoparasitoid whose larvae develop in the host haemocoel and avoids the host immune system. In this study, we investigated the immune evasion mechanisms of this species during infestation in the host Mythimna separata (Lepidoptera: Noctuidae). We discovered a unique ‘cloak’ that surrounded D. inconspicuoides larvae that penetrated into the host and determined through genomic polymerase chain reaction analysis that this structure originated from the host rather than the tachinid. The ‘cloak’ contained both haemocytes and fat body cells from the host, with the haemocytes assembling around the larvae first and the fat body cells then covering the haemocyte layer, following which the two mixed. Living D. inconspicuoides larvae that were wrapped in the ‘cloak’ were not melanized whereas encapsulated dead larvae were melanized, suggesting that this structure contributes to the avoidance of host immune reactions.

Grape phylloxera, Daktulosphaira vitifoliae Fitch, is an important pest of grapevines (Vitis vinifera L.) (Vitaceae). The distribution and frequency of phylloxera clone lineages vary within infested regions of Australia, suggesting the introduction of separate lineages of D. vitifoliae with host associations. Virulence levels of particular phylloxera clones may vary on V. vinifera, but much of this evidence is indirect. In this study, we directly tested the performance of phylloxera clones on V. vinifera using an established excised root assay and a new glasshouse vine assessment. In the root assay, grape phylloxera clones differed in egg production and egg to adult survivorship. In the vine assay, clones differed in the number of immature and adult life stages on roots. In addition vine characteristics, including mean stem weight, root weight, leaf chlorophyll and leaf area, were affected by different phylloxera clones. The two most widespread clones displayed high levels of virulence. These results point to only some phylloxera clones being highly virulent on V. vinifera, helping to explain patterns of field damage, phylloxera distributions and continued survival and production of V. vinifera vines in some infested areas.

A commercially-available, hand-applied PVC resin formulation of the sex pheromone of the striped rice stem borer, Chilo suppressalis (Walker) was used to control the yellow stem borer, Scirpophaga incertulas (Walker), in a 20 ha mating disruption trial in West Bengal, India, in 1992. Indirect measures of mating disruption were used to compare the pheromone-treated plot with an untreated control plot and a farmers' practice plot where a conventional pesticide control regime was practised. The results showed that the level of ‘white head’ damage in the pheromone-treated plot was significantly lower than that recorded in other treatment plots and that the relative percentage of the larvae of the two major stem borer species, S. incertulas and Chilo polychrysa (Meyrick) found in the region changed from 88% S. incertulas in the farmers' practice plot to 65% in the pheromone-treated plot. The yields of grain and straw recorded in the pheromone-treated plot were significantly higher than in the untreated control plot but not significantly different from those recorded in the farmers' practice plot.

1. There is considerable seasonal variation in the longevity of G. submorsitans and G. tachinoides, and these variations are negatively correlated with the fluctuations in the maximum temperature curve, i.e., as the temperature rises longevity decreases, as the temperature falls so longevity increases.

2. The cycle is as follows:—The rains commence and temperature falls, longevity increases and remains high throughout the rains. The wet season ends, temperature rises and longevity descreases. The cold spell intervenes and longevity becomes maximal. The cold weather ends, the temperature soars up and longevity becomes minimal, remaining low until the new rains commence.

3. Maximum temperature is considered to be the dominant factor; favourable humidity cannot increase longevity unless the maximum temperature is favourable.

4. The oldest individuals occur in the rains, but the average longevity is highest in the cold season, when both temperature and humidity are favourable.

5. In both species females tend to live longer than males.

6. In the field G. tachinoides males appear to live rather longer than the males of G. submorsitans.

7. It is doubtful whether wild flies of either species live much more than 2½ to 3 months under the most favourable conditions; it is probable that in the hottest weather longevity is curtailed to a month or less, and that the production of puparia is seriously affected when the rains are late and the hot weather is prolonged.

Surplus puparia from a colony of about 50 000 females of Glossina morsitans morsitans Westw. provided males for sterilisation and release in an experimental assessment of the sterile insect technique in Tanzania. Excess males were stored late in the puparial stage at 10 ±1°C for up to four days prior to being irradiated at ambient temperatures in a nitrogen atmosphere with 11·8 krad in a radioactive caesium (137Cs) source. Puparia chilled at 8 ± 1°C were transported to the field release area twice weekly for manual release. At the release sites, the adults emerged synchronously within 60 min and were automatically marked as they crawled through sand containing fluorescent powder.

A semi-defined synthetic diet for Glossina spp. was developed and used successfully to rear G. palpalis palpalis (Robineau-Desvoidy) for five generations. The survival, fecundity and offspring size achieved were similar to those obtained when flies are fed on whole blood in vitro. The diet was also tested on G. morsitans morsitans Westwood, G. austeni Newstead and Stomoxys calcitrans (L.), and in all cases was satisfactory. The diet consists of commercially available ingredients and is the first such diet to be developed for obligate haematophagous insects.

Parasitoids of Aonidiella aurantii (Maskell) on citrus in South Africa were monitored using two types of yellow sticky trap. One of these traps was highly efficient, being fluorescent with peak reflectance at about 530 nm. Aphytis spp. populations were low before February and high thereafter. Citrus surrounded by natural bush was an isolated reservoir of high host and parasitoid population levels. Aphytis spatial distribution within the orchard was extremely patchy, with over 100-fold differences in population levels over a distance of a few metres. This patchiness mirrored that of its host. This contagious spatial pattern was maintained despite 1000-fold seasonal changes in population levels. These temporal changes were characteristic and general throughout an orchard, and independent of patchiness. Initial Aphytis population levels did not dictate the final population level at the end of the season. Comperiella bifasciata Howard and its hyperparasitoid Marietta javensis (Howard) also showed clear seasonal population trends, but not of the same magnitude as those of Aphytis. There was no statistically significant correlation between the spatial distribution of one parasitoid with that of another, even between C. bifasciata and M. javensis. The patchiness of these two species was not correlated with overall host density. Aphytis and C. bifasciata were partially mutually exclusive. Aphytis was by far the most economically important of the parasitoids. Pest management practices, therefore, should aim at conserving the pool of Aphytis within the orchard as far as practicable.

Two experiments are described where applications of coarse aerosols have been made to areas of savannah woodland infested with tsetse flies (Glossina spp.).

The applications were made at nominal dosages of 0·25 gallons per acre, which was equivalent to either 0·20 lb. of p.p′DDT per acre, or 0·03 lb. of γ BHC per acre. The coarse aerosols had mass median diameters of approximately 60 microns.

In one experiment, carried out at Urambo, Tanganyika, a reduction of 95 per cent, was obtained in populations of G. morsitans Westw. This kill was somewhat lower than in many other experiments, a fact that can be attributed mainly to our inability to maintain the cycle of applications. Immigration of flies into the treated area caused a relatively rapid increase in fly numbers to levels comparable to the pre-treatment populations, and in this respect the experiment was a failure.

The other experiment, in Lango County, Uganda, was highly successful, and reduced a population of G. morsitans to 0·05 per cent, of its pre-treatment level, and eradicated a small population of G. pallidipes Aust. It is indeed likely that no stable population now exists in the area, and that the very few flies caught there since the end of the applications have been wanderers from other infested woodland. The continued success of the experiment is considered to be due to the effective isolation of the area.

Some brief comments are made upon the costs of the method, and on its value under conditions of land development in Africa.

The genus Schistocerca is one of very great economic importance, since it includes the Desert locust of the Old World, Schistocerca gregaria (Forsk.) and the South American locust, S. paranensis (Burm.). It was therefore considered of value to study the life history of one of the solitary species living in Trinidad, and the present investigations were made during 1942 at the Imperial College of Tropical Agriculture at St. Augustine.

The climate of Trinidad is humid tropical. The annual rainfall over nineteen years at St. Augustine averaged 68·4 inches, but in the north-east of the Island the rainfall is over 100 inches per annum, falling to below 60 inches on the West coast. The rainy season usually begins about June, with a break in August or September, and lasts till the end of the year or the early part of January. November may be taken as one of the wettest months with a rainfall of about 11·5 inches (at St. Augustine), while more than half an inch is not usual for April. The humidity in November averages about 85 per cent. in the morning and 77 per cent. in the afternoon, but it is still high in April, being 75 per cent. and 64 per cent. for morning and afternoon respectively. The night humidities are even higher. The temperature remains practically constant throughout the year, averaging about 84°F. (29°C.) during the day, and 74°F. (23·3°C.) at night. The temperature may reach 95°F. (35°C.) during the day in the dry season, but it seldom falls as low as 65°F. (18·3°C.) at night.

Cattle kept at the Latoli kraal of the Indian Veterinary Research Institute at Mukteswar in the Kumaon foothills of the Himalayas were heavily infested with the tick Boophilus microplus (Can.). In order to reduce the infestation, the animals were treated with BHC dusts every season for a number of years. In 1960, it was noticed that the treatment was not as effective as in the previous years. A series of concentration/response tests was therefore carried out in 1961–62 to see whether or not the tick had developed any resistance to BHC. Ticks collected from cattle in a village about five miles distant, where no acaricide had ever been applied, were used as the standard for comparison. BHC as a wettable powder was used to provide six different concentrations of γ BHC for engorged females and unfed larvae, respectively. Treatment was by appropriate dipping techniques. Analysis of the results showed that the population of B. microplus infesting cattle at the Latoli kraal had developed resistance to BHC. The LC50's of γ BHC for engorged females and unfed larvae, respectively, of the Latoli population were 0.5164 and 0.0182 per cent., and of the village population 0.0834 and 0.00069 per cent. This seems to be the first record of any species of tick developing resistance to an acaricide in India.

It was found that the mean number of eggs laid per tick in the control batches was higher in the village population than in the Latoli population and that the difference was highly significant.

Zonocerus variegatus (L.) is a chronic but relatively minor pest of crops in West Africa, and expensive control measures are not generally warranted. Egg pods, which take approximately six months to develop, are deposited in highly aggregated sites found scattered throughout cultivated areas. To test the feasibility of reducing populations in large areas by digging up the egg pods, two areas, of 18·5 and 20 ha, were selected near Ibadan, Nigeria, for investigation. Egg-laying sites were identified by observation and the egg pods subsequently dug up. There were on average one or two sites, 5·7 m2 in area, per hectare. Counting the following season's hatching populations in the two areas showed that the potential hatches had been reduced by 83 and 91%, respectively. Control by community self-help is suggested, where individual farmers identify and dig up laying sites on their own land, exposing the egg pods to desiccation on the soil surface. If this was carried out by all the farmers in an area, populations of Zonocerus could be reduced and crop damage minimised. Such control can be carried out at little or no cost and with very little labour.

The oyster-shell or mussel scale (Lepidosaphes ulmi, L.) (fig. 1) is too well known to need any particular introduction ; suffice it to say that this insect has followed its principal food-plant, the apple tree, over the world. Though usually considered a serious pest in places in which it has been long established, such as England and

Canada, it is not increasing. There must then be agencies at work destroying annually about 98 per cent. of the progeny of each pair of scales. In different countries these agencies may differ greatly. It is the purpose of the present paper to give a general outline of the principal factors operating in the control of this scale in Canada, and more especially in Eastern Canada. The study, which has been carried on under the direction of the Dominion Entomologist, Dr. C. Gordon Hewitt, is based on the literature of the subject and on the examination of about eighteen thousand egg-masses of scales collected, between September 1916 and April 1917, from representative places throughout Canada. Most of this material was gathered by the officers and friends of the Entomological Branch and mailed to the Dominion Entomological Laboratory at Fredericton, N.B., for examination. The names of these gentlemen appear in the analysis table (on page 191) opposite their respective collections and it is a pleasure to acknowledge their kindly assistance. Each 100 of these egg-masses was, so far as practicable, an average 100 selected from several twigs of one tree or bush. So far as possible, collections were made from five trees or bushes at each observation point.

Experiments in the glasshouse have confirmed that spraying virus-source leaves or test plants with mineral oil (liquid paraffin) inhibits transmission of beet yellows virus (BYV) to sugar-beet by Myzus persicae (Sulz.). Spraying M. persicae with oil after feeding on BYV-infected leaves and before transfer to virus-free beet seedlings also inhibited their transmission of BYV. The appearance of systemic symptoms of BYV was not delayed by treatment of the test plants or the aphids with oil. The effects of oil on virus transmission were reflected in adverse effects of oil on the settling behaviour and larviposition of the vector on test plants. It is suggested that coating the stylets with oil inhibits the feeding of aphids in the phloem thereby decreasing the efficiency of BYV transmission. The effects of oil on aphid settling and larviposition suggest that spraying crops with oil may not only reduce the incidence of aphid-transmitted viruses in them but may also diminish the population of potential vectors present in them.

Interference competition between closely related alien and indigenous species often influences the outcome of biological invasions. The whitefly Bemisia tabaci species complex contains ≥28 putative species and two of them, Mediterranean (MED, formally referred to as the ‘Q biotype’) and Middle East-Asia Minor 1 (MEAM1, formally referred to as the ‘B biotype’), have recently spread to much of the world. In many invaded regions, these species have displaced closely related indigenous whitefly species. In this study, we integrated laboratory population experiments, behavioural observations and simulation modelling to investigate the capacity of MED to displace Asia II 1 (AII1, formally referred to as the ‘ZHJ2 biotype’), an indigenous whitefly widely distributed in Asia. Our results show that intensive mating interactions occur between MED and AII1, leading to reduced fecundity and progeny female ratio in AII1, as well as an increase in progeny female ratio in MED. In turn, our population cage experiments demonstrated that MED has the capacity to displace AII1 in a few generations. Using simulation models, we then show that both asymmetric mating interactions and differences in life history traits between the two species contribute substantially to the process of displacement. These findings would help explain the displacement of AII1 by MED in the field and, together with earlier studies on mating interactions between other species of the B. tabaci complex, indicate the widespread significance of asymmetric mating interactions in whitefly species exclusions.