These experiments were performed in response to a question submitted to me from the Royal Sanitary Institute. The point at issue was the possibility of eggs of the common bed-bug, Cimex lectularius, surviving the process of house-destruction, when the plaster from old walls, on which eggs had been laid, was broken down and remixed with fresh mortar for making the partitions of rooms in new tenements; such survival having been given as an explanation for previously unoccupied houses being infested with bugs.

Macrolophus pygmaeus is commercially employed in the biological control of greenhouse and field vegetable pests. It is morphologically undistinguishable from the cryptic species M. melanotoma, and this interferes with the evaluation of the biological control activity of M. pygmaeus. We analysed the potential of cuticular hydrocarbon composition as a method to discriminate the two Macrolophus species. A third species, M. costalis, which is different from the other two species by having a dark spot at the tip of the scutellum, served as a control. Sex, diet and species, all had significant effects in the cuticular hydrocarbon profiles, but the variability associated to sex or diet was smaller than among species. Discriminant quadratic analysis of cuticular hydrocarbons confirmed the results of previous molecular genetic studies and showed, using cross-validation methods, that M. pygmaeus can be discriminated from M. costalis and M. melanotoma with prediction errors of 6.75% and 0%, respectively. Therefore, cuticular hydrocarbons can be used to separate M. pygmaeus from M. melanotoma reliably.

This paper deals with the aerial curtain method of spraying flying swarms of locusts with insecticide from aircraft.

Equations are developed for calculating the dosage deposited on locusts in single spraying runs under idealised conditions. Graphical methods of solving the equations are described together with a simple method for obtaining the summed effect when a number of spraying runs are carried out in a regular sequence to form an aerial curtain.

There is an optimum combination of spray droplet size distribution and spraying height according to the depth and density of the swarm, but good performance can be obtained with a single fixed droplet size distribution. A fine spray is recommended for the attack of flat-topped, shallow swarms, but a coarser spray is required to penetrate adequately into deeper and denser swarms.

The efficiency of application of the insecticide solution, calculated as the proportion of lethal doses actually applied to those potentially available, may be as high as 10 per cent., but varies rapidly with spray droplet size and swarm characteristics.

The numerical values given may need some modification in the light of further experimental and field data, especially in regard to locust airspeed in the swarm and the effect of droplet size on mortality.

Heteroplasmy is the existence of multiple mitochondrial DNA haplotypes within the cell. Although the number of reports of heteroplasmy is increasing for arthropods, the occurrence, number of variants, and origins are not well studied. In this research, the occurrence of heteroplasmy was investigated in Thrips tabaci, a putative species complex whose lineages can be distinguished by their mitochondrial DNA haplotypes. The results from this study showed that heteroplasmy was due to the occurrence of mitochondrial cytochrome oxydase I (mtCOI) haplotypes from two different T. tabaci lineages. An assay using flow cytometry and quantitative real-time PCR was then used to quantify the per cell copy number of the two mtCOI haplotypes present in individuals exhibiting heteroplasmy from nine geographically distant populations in India. All of the T. tabaci individuals in this study were found to exhibit heteroplasmy, and in every individual the per cell copy number of mtCOI from lineage 3 comprised 75–98% of the haplotypes detected and was variable among individuals tested. There was no evidence to suggest that the presense of lineage-specific haplotypes was due to nuclear introgression; however, further studies are needed to investigate nuclear introgression and paternal leakage during rare interbreeding between individuals from lineages 2 and 3.

The following article includes the results of observations on the number and species of mosquitos breeding in two tree-holes during a period of more than ten months.

A total of 15 835 ticks was identified, mainly from sheep and goats, in a livestock survey in Cyprus in 1970–72. Hyalomma anatolicum anatolicum Koch, H. a. excavatum Koch, H. marginatum marginatum Koch, H. m. turanicum Pom., H. m. rufipes Koch, Haemaphysalis sulcata C. & F., Ixodes crenulatus Koch and Rhipicephalus turanicus Pom. & Matikashvili are recorded for the first time in Cyprus. H. sulcata was found in all parts of the island; Hyalomma spp. and Rhipicephalus spp. were mostly seen in the low drier areas, and Ixodes gibbosus Nutt. in the wetter areas; Boophilus annulatus (Say) was confined to one small area. Ticks were most common in autumn and early winter. Haemaphysalis sulcata and I. gibbosus were only found in the winter months, whereas Hyalomma spp. were found all the year round but especially in the warmer months. The Hyalomma subspecies showed some differences in seasonal distribution. Immature Rhipicephalus ticks were found in the colder months whereas the adults were seen mainly in the spring and early summer. Immature Haemaphysalis sulcata and Hyalomma spp. were extremely rare on ruminants. Only adults of I. gibbosus were seen in the first year of the survey, whereas only immatures, mainly larvae, were seen in the second year. The period of attachment of R. bursa C. & F. adults was shorter than that of R. turanicus and corresponded closely to the incidence of babesiosis in sheep and goats. The predilection sites of ticks for cattle, sheep and goats are given.

Field populations of Musca vetustissima Walker were sampled in a region of New South Wales at 2-h intervals on 35 occasions between spring 1984 and autumn 1985 using wind-oriented fly traps. Ambient temperature, solar radiation, relative humidity and wind speed explained 84·3% of the within-day deviance of total catches (both sexes combined). Temperature and solar radiation jointly explained 82·6% of this deviance (71·1 and 11·5%, respectively), indicating that the other variables, although significant, did not greatly affect trap catches. As air temperature increased, log catch rates increased non-linearly up to a maximum at 27·5°C and declined thereafter. Log catch rates increased linearly as solar radiation increased and declined linearly as relative humidity and wind speed increased. Changes in log catch rates with time of day were explained almost entirely by the four weather variables, i.e. when weather effects were removed, time of day effects were no longer significant. These weather variables also accounted for 79·9% of the between-day variation in logarithms of trap catches. Relative responses of males and females to traps differed significantly with respect to relative humidity, wind speed and time of day. Male catches tended to increase relative to female catches between 1200 h and 1800 h and also declined more slowly with increases in relative humidity and wind speed. Separate models are presented for standardization of male and female catch rates; the estimates differ from those obtained from observed sex ratios and total catch rates, but the differences are small compared to the observed day-to-day variation in catch rates.

Some flightworthy alate exules of Aphis fabae Scopoli reproduce before taking off while others do not. This difference in behaviour is influenced by crowding and has previously been taken as an indication of the urge to migrate, although it has never been conclusively demonstrated. In this study, the flight performance of those aphids depositing some nymphs before take-off (‘flyers’) was compared with those which did not (‘migrants’). In fact, no significant difference was found between migrants and flyers in any of the aspects of post-take-off flight or settling behaviour tested. In tethered flight, large alatae flew for longer than small ones, irrespective of their pre-flight reproductive behaviour. In free flight, however, large alatae flew for a shorter period before actively landing on a plant. Large alatae were also subsequently more reluctant to leave the plant than small alatae, spending more time in sedentary activities such as probing and less time preparing to take off. It is concluded, therefore, that migratory urge is related more to aphid size, a product of plant nutritive quality, than to take-off urge, as measured by pre-flight reproductive behaviour. However, as high population densities tend to occur when the nutritional quality of the host is declining, take-off urge and migratory urge are likely to be synchronized in the field.

Detailed studies were conducted over a five-year period at a rice farm in the Philippines on the flight activity of Nilaparvata lugens Stål) and Sogatella furcifera (Horváth). Suction traps were used to measure aerial density, and catches included immigrants, emigrants and insects undertaking trivial flight. Activity was partitioned using a variety of other trap types. Emigration was effectively monitored using net canopy traps and immigration was best measured using green water traps. Yellow water traps also measured immigration, but when macropterous adults were being produced within the plot, insects undertaking trivial flight were also caught. The light-trap caught immigrant and over-flying migrant insects.

Opisina arenosella Walker is a defoliating pest of coconut in Sri Lanka. A first attempt was made to understand its population dynamics. Analysis of records of population outbreaks throughout the country from 1965 to 1985 revealed cycles in the population of approximately one generation period, giving the population the appearance of partially discrete generations. There was also evidence for longer cycles of six-month period. Outbreaks occurred throughout the coconut-growing regions of Sri Lanka, and the numbers of outbreaks per year in different provinces were sometimes correlated, indicating a common, probably climatic, triggering mechanism. Parasitism remained high throughout the outbreaks and there was some evidence that pupal parasitism increased towards the end of an outbreak. A working hypothesis that explains the population dynamics of O. arenosella and the origin of outbreaks is presented.

Circadian flight activity in Anopheles stephensi List. has been investigated using the acoustic aotograph technique. In alternating 12 h light: 12 h dark (50 or 200 lx), both sexes are active during the dark period, with peaks of activity following light-off and light-on. Cyclical activity persists in constant dark and is inhibited and reset by prolonging the light period. There are small differences between the carriers of the alternative chromosomal arrangements 2R+ ( +/+) and 2Rb (b/b) and between the sexes. In +/+ females the period of the cycle in constant dark is approximately half-an-hour longer and, in LD 12:12, there is less activity at light-on than in both sexes of b/b or in +/+ males. The +/+ males appear to be less susceptible to the inhibitory effect of prolonging the light period, although the cycle is reset.

An experiment to ascertain whether extermination of Glossina pallidipes could be brought about by introducing large numbers of DDT-treated oxen into its habitat was carried out in a small isolated block of bush in Tanganyika.

The oxen were sprayed with a solution of 9 per cent, w/v pure DDT and 9 per cent, w/v resin in groundnut oil. It was estimated that when sprayed once weekly about 70 per cent, of tsetse settling on them were killed, and when sprayed twice weekly, about 95 per cent. Oxen so treated were introduced in a numerical superiority of about 6 to 1 over the larger game in the bush, but were fewer than the small game.

After 3 months in which oxen sprayed once weekly were herded in tens in the bush for ten hours each day, the population of female tsetses was reduced by about 70 per cent. After a further 2 months in which oxen sprayed twice weekly were herded in fives a reduction of 80 per cent, amongst the survivors was brought about.

Aggregative responses are commonly observed in insects, including chrysomelids, affecting both individual and population growth rates. In two closely related chrysomelid beetles (Galerucella calmariensis and G. pusilla) feeding on purple loosestrife (Lythrum salicaria), recent studies suggest that male-produced pheromones may cause both inter- and intraspecific attraction. This paper further examines the causes and consequences of feeding aggregations in these species. Olfactometer studies confirm previous findings, showing cross-species attraction to damaged plants, but suggest that also damaged induced plant volatiles may be involved. In addition, the studies suggest that the cross-species attraction observed in previous studies have asymmetric effects on the two beetles. Galerucella pusilla was more attracted to damage by G. calmariensis than to damage by conspecifics. Laboratory and field data suggest that feeding aggregations in these species increase pupal mass, at least at low to intermediate larval densities. This positive feedback may have important consequences for the spatiotemporal dynamics and as a consequence on the role of the two chrysomelid beetles on biological control of purple loosestrife.

Introduction of parasitoids gave improved biological control of Planococcus citri (Risso) in a large glasshouse stocked with a variety of ornamental plants, supplementing that achieved by the predator Cryptolaemus montrouzieri Mulsant. Following parasitoid release, there was evidence of pest population regulation on guava and coffee bushes with reduced and stabilized mealybug numbers and stable percentage parasitism. The mean temperature during one sampling period was significantly correlated with the percentage parasitism two months later, indicating that temperature has a major impact on parasitoid efficiency. Leptomastidea abnormis (Girault) was responsible for about 90% of the parasitism observed; the remainder was by Leptomastix dactylopii Howard. The effects of supplementary inoculative releases of Leptomastidea abnormis were variable, but resulted in increased percentage parasitism only when the number released contributed significantly to those already established. No evidence of pest population regulation was found on Aristolochia or Passiflora vines nor on potted Gesneriaceae plants of the genera Streptocarpus and Saintpaulia. Peak mealybug populations on these last plants coincided with periods of new growth, fruiting or flowering. Host-plant quality thus seems to be a major factor inducing mealybug outbreaks.

Antibiosis and resistance of six Cucurbita and two Lagenaria accessions to the carmine spider mite, Tetranychus cinnabarinus Boisduval, were evaluated in the laboratory. Significant differences among accessions were observed three days after the inoculation of detached leaf discs. The Lagenaria accessions, Slawi and Sus, proved to be the most resistant to mites, with average populations of mite eggs, 87 and 95%, respectively less than that of the susceptible C. pepoaccession, Orangetti. The Cucurbita accessions, Tace, Brava, Tetsukabuto, Phoenix and TZ-148 had mite egg totals 4, 9, 13, 26 and 40%, respectively, less than those of accession Orangetti. The Sus accession of Lagenaria was resistant to T. cinnabarinus from the four-leaf stage until fruit set in laboratory and field tests. Grafting the susceptible Brava onto Sus rootstock increased the resistance of the scion to the same level as that of non-grafted Sus. Grafting the susceptible Cucumis melo Noy Yizre’el on resistant or susceptible rootstocks of Cucurbita and Lagenaria accessions did not affect its susceptibility to T. cinnabarinus. The results indicate that resistance to T. cinnabarinuscan be transferred by grafting from Lagenaria stocks to Cucurbita scions but not in the opposite direction.

Mosquitos in the genera Uranotaenia and Ficalbia seldom bite man. In Africa, only two species, U. alboabdominalis Theo. and F. plumosa, (Theo.), have been taken actually engorging on man, though others may occasionally alight on the skin.

Hodgesia cyptopus Theo. bites man freely in forest, bush and plantations near Entebbe, Uganda, and sometimes enters houses.

The bimodal nature of the biting cycle of H. cyptopus in certain series of catches led to an investigation of the daily march of light intensity near the forest floor. It was found that at least in some areas this is bimodal, with a midday period of lower intensity—a pattern reflected in the biting behaviour of various forest mosquitos.

Though always diurnal, the biting cycle of H. cyptopus varies in form from station to station. It is thought that light intensity is of importance, and that this species probably bites in or around the small splashes of sunlight which penetrate the dense vegetation.

Plant sugars are often considered as primary feeding stimuli, conditioning host plant acceptance by herbivorous insects. Of the nine sugars identified from methanolic extracts of seven grass species, only turanose, a sucrose isomer, was negatively correlated with the survival and growth of the noctuid larva of cereal stemborer, Busseola fusca. Sucrose was the most abundant sugar, although it did not vary significantly in concentration among the plant species studied. Using Styrofoam™ cylinders impregnated with increasing concentrations of turanose or sucrose, the two sugars had opposing effects: turanose appeared phagodeterrent while sucrose was phagostimulatory. Electrophysiological studies indicated that B. fusca larvae were able to detect both sugars via their styloconic sensilla located on the mouthparts. The findings indicate that, whereas sucrose is a feeding stimulant and positively influences food choice by B. fusca larvae, turanose negatively contributes to larval food choice. The balance in concentrations of both sugars, however, somehow influences the overall host plant choice made by the larvae. This can partly explain host plant suitability and choice by this caterpillar pest in the field.

The objective of this work was to study the effect of colony waste on the mortality of workers of Atta sexdens rubropilosa Forel colonies fed with different plant substrates. Eight nests were used; two colonies each were fed with Acalypha wilkesiana Müller.Arg, Ligustrum japonicum Thunb, Eucalyptus urophylla S.T. Blake or a mixture of the three substrates in equal proportions. Irrespective of diet, being kept with waste led to higher mortality. However, workers that were kept in contact with waste produced by colonies fed Acalypha had higher average survival rate and later death when compared with workers from the other treatments. Workers from the Eucalyptus-fed colonies had the lowest survival rate and 50% of them died within four days of exposure to Eucalyptus waste. Trichoderma viride Pers. ex Gray, a fungus garden antagonist, and the entomopathogen Aspergillus flavus Link. ex Gray were present in the colonies supplied with all plants. The largest fungus diversity was verified in the waste of colonies fed Acalypha and the mixture of Acalypha, Ligustrum and Eucalyptus. Therefore, antibiotic properties of Acalypha did not reduce contaminant diversity but apparently minimized effects of pathogenic microorganisms present in the waste such as Asp. flavus. This may explain the highest survival rate of workers in this treatment.

Samples of Glossina longipennis Corti, taken over four days in traps (baited with acetone, cow urine and octenol) at half-hourly intervals during their restricted activity periods at dusk and dawn, were analysed for their nutritional condition. For both sexes, trap catches were highest at the end of dusk, between 19.00 and 19.30 h, associated with a significant increase in numbers with the low haematin content characteristic of flies estimated to have fed more than 60 hours previously. Also, the mean fat content of these flies was significantly lower than that of those trapped earlier. There was considerable day-to-day variation in the numbers of flies trapped, and in the numbers of low haematin and low fat flies. It is concluded that the nutritional condition of the fly probably influences the timing of the onset of activity, but possibly the fly's approach to the trap.

Trissolcus crypticus sp. n., a sibling species of T. basalis (Wollaston), is described. Introduced from Pakistan into Australia and Hawaii (via Australia) as a ‘strain’ of T. basalis, it was widely released for the biological control of Nezera viridula (Linnaeus). In Australia, the species reputedly gave widespread control of N. viridula populations in inland and northern areas. Examination of all available T. basalis specimens in Australia failed to discover any T. crypticus (other than voucher specimens) and its role as a biological agent warrants reassessment.