A long series of breeding experiments were conducted by the writer at the Malaria Bureau, F.M.S., between April 1920 and April 1921 with a view to obtaining in bred families a sufficiency of Anophelines for the purpose of study which might perhaps set at rest, once and for all, various long-vexed questions as to the validity of certain species; and for the purpose of obtaining further data than were previously available as to the bionomics of the insects.

The effects of tetramethrin on the behaviour and mortality of Anopheles gambiae Giles entering verandah-trap huts have been studied with the assistance of gaschromatographic techniques.

Fifty-three to 39% of A. gambiae were deterred from entering a corrugated-iron-roof hut treated indoors with a nominal dosage of 2 gm/m2 tetramethrin active ingredient.

Overall mortalities were 53–71% in the first month of application, but fell two to three months after application to 22–46%.

The tetramethrin deposit had marked effects on the behaviour of A. gambiae entering treated huts. Feeding was greatly inhibited, 69–90% of the mosquitoes being unfed. Also, as the residual toxicity of the deposit declined, increasingly higher proportions (40–70%) of recently blood-fed A. gambiae left the huts due to the irritant action of the insecticide. The chemical basis of the irritant effect was indicated to the extent that survivors leaving the treated hut showed 9·5–14·0 ng tetramethrin/individual. The minimum lethal dose was indicated by 17·5–21·7 ng/individual picked up by mosquitoes showing delayed mortalities after leaving the treated huts. Mosquitoes that died indoors picked up amounts ranging from 27·0 to 42·3 ng/individual.

The effects of tetramethrin on A. gambiae were in general similar to those of DDT and pyrethrum, and differed only in degree.

Records of Leucoptera coffeella (Guér.) from Kenya and Tanganyika have been found to be based on misidentifications and to refer to a distinct species, Leucoptera meyricki Ghesq. Other records of coffeella from the Old World seem open to doubt and require to be reinvestigated since they may also be based on misidentifications. L. coffeella seems likely to be a Neotropical species predominant in the West Indies. A lectotype is designated for meyricki, but the type material of coffeella cannot be traced and the identity of the latter species remains to be properly established. The present generic assignment of meyricki and coffeella in the genus Leucoptera Hübn. needs to be reconsidered in the light of the new genus Perileucoptera Silvestri (1943).

The pyrethrins, nicotine, rotenone and a derris resin have been tested in the laboratory under standard conditions for their ovicidal effect. The test-subjects were : Pieris brassicae, Plutella maculipennis, Aphis rhamni, Ephestia kühniella and Sitotroga cerealella. Notes on the technique of egg production are given for these species. In the majority of the tests made a water medium containing acetone together with sulphonated lorol as a wetting agent was used.

It has been shown that all these products are toxic to the species on which they were tested. Lauryl thiocyanate, β-butoxyβ'thiocyanodiethyl ether and 3 : 5 dinitro-o-cresol were included as substances of recognised ovicidal value for purposes of comparison.

All the above insecticides derived from plants compared favourably in their toxic action with the synthetics. In two instances during tests on eggs of Ephestia kiihniella, data were obtained enabling a satisfactory statistical comparisdn of relative potency to be made. In the first of these, the pyrethrins were found to be 8·45±1·47 times as toxic as 3 : 5 dinitro-o-cresol, while in the second the pyrethrins were found to be 2·66±0·26 times as toxic as a Derris elliptica resin (rotenone content 37–40 per cent.). It therefore appears that both the pyrethrins and the derris resin were more toxic, weight for weight, than 3 : 5 dinitro-o-cresol which is recognised as one of the most potent ovicides.

The above vegetable poisons were found to be toxic not only to eggs developing in a few days without a diapause, but also to those of Aphis rhamni, a species of overwintering egg. The tests on A. rhamni were made at the time the eggs were just starting to hatch. The same result might not have been obtained with eggs at an earlier stage of development.

Observations were made on the effect of the different insecticides on the development of the egg. This effect appeared to differ with each substance, either qualitatively or quantitatively, but within the limits of the experiment it seemed to be independent of the species of the egg.

Disentangling the responses of insects to variations in their thermal environment is central to our understanding of the evolution of temperature-dependent performance in these species. Here, we report results of experiments examining the effects of high (upper lethal temperature = ULT) and low (lower lethal temperature = LLT) temperature and exposure time on the survival of larvae and adults of a multivoltine, nocturnal moth species, Pareuchaetes insulata, a biological control agent whose impact on an invasive weed, Chromolaena odorata has been variable in South Africa. The influence of temperature and acclimation on locomotion performance of the moth was also investigated. Temperature and duration of exposure significantly affected survival of both adults and larvae of P. insulata with more extreme temperatures and/or longer durations proving to be more lethal. Third instar larvae and adults are both freeze intolerant and had LT50 of −5.9 and −4.7°C, respectively, after a 2 h exposure. Although cold acclimation was beneficial to the nocturnal larvae, temperatures below 10°C significantly reduce their locomotion activities. The average daily minimum temperatures in the coldest months at three locations in South Africa are over 5°C lower than those of Fort Lauderdale, Florida, USA, where P. insulata was originally collected. Our results suggest that lethal high or low temperatures at short timescales are trivial in explaining the variable performance of P. insulata, but reduced locomotion at sub-lethal temperatures may be an important driver of the population dynamics of the biocontrol agent (especially in winter months) and may consequently explain the low population levels of the moth because of possible reduced feeding by larvae during night-time low temperatures.

Cultivating plant mixtures is expected to provide a higher productivity and a better control of pests and diseases. The structure of the arthropod community is a major driver of the magnitude of natural pest regulations.

With the aim of optimizing pest management, a study was carried out to determine the effect of the cropping system type (tomato mono-cropping vs. mixed-cropping) on the diversity and abundance of arthropods from three trophic groups (herbivores, omnivores, predators) and the abundance of Helicoverpa armigera. Therefore, the diversity of cultivated plants and arthropod communities was assessed within tomato fields from 30 farmer's fields randomly selected in South of Benin. Results showed that the arthropod abundance was significantly higher in mixed-cropping systems compared with mono-cropping systems, although the crop type did not alter significantly the arthropod diversity, evenness, and richness. At the level of taxa, the abundances of generalist predators including ants (Pheidole spp., and Paltothyreus tarsatus) and spiders (Araneus spp. and Erigone sp.) were significantly higher in mixed fields than in mono-crop fields. Then, the abundances of omnivore-predator trophic groups have a negative significant effect on the H. armigera abundance. This study allowed better understanding of how plant diversity associated to tomato fields structures arthropod's food webs to finally enhance the ecological management of H. armigera.

A hand-applied ‘twist-ti’ pheromone formulation containing the combined pheromones of Pectinophora gossypiella (Saunders) (Gelechiidae), Earias vittella (Fabricius) and E. insulana (Boisduval) (Noctuidae) was used in trials conducted in Pakistan from 1986 to 1988. In plots of cotton ranging in area from 2.8 to 6.0 ha, season-long control of the bollworm complex was achieved using the pheromone formulation applied alone or together with one conventional insecticide treatment, with the conventional insecticide spray programme requring up to five applications of insecticide to achieve a similar level of control. No significant differences were found in yield estimates from plots treated with pheromones compared with plots receiving conventional insecticide treatments. Significantly higher levels of boll infestation and lower yield estimates occurred in control plots where neither pheromones nor insecticides were applied.

(1) The life-history of S. destructor was investigated, and it is shown that it is primarily a saprophagous feeder but with distinct potentialities for occasional parasitism.

(2) Two species of parasites were bred out of Locusta and Schistocerca from the Red Sea Coast: Blaesoxipha lineata, Fall., and B. filipjevi, Rohd.

(3) The percentage of parasitism was high; 39 per cent. of the adults examined in the area in December 1932 either contained parasites, or had been parasitised and recovered.

(4) The recovery from parasitism was high; 19 per cent. of the locusts examined had been parasitised and recovered.

(5) The life-history of B. lineata and B. filipjevi was investigated in the laboratory; Olsuf'ev's observation that B. lineata is not a very effective parasite was confirmed. A 78 per cent. recovery from parasitism by B. lineata was obtained. Only 38 per cent. of the locusts parasitised reproduced.

Insect cell lines provide useful in vitro models for studying biological systems, including interactions between mosquitoes and obligate intracellular endosymbionts such as Wolbachia pipientis. The Aedes albopictus Aa23 cell line was the first cell line developed to allow examination of Wolbachia infections. However, Wolbachia studies using Aa23 can be complicated by the presence of different cell types in the cell line and the substantial temporal variation in infection level. Two approaches were examined to ameliorate infection variability. In the first approach, multiple Aa23 passaging regimes were tested for an effect on infection variability. Fluorescence in situ hybridization (FISH) staining was used to characterize Wolbachia infection level over time. The results demonstrate an impact of passaging method on Wolbachia infection level, with some methods resulting in loss of infection. None of the passaging methods succeeded in effectively mitigating infection level variation. In a second approach, the clonal C7-10 A. albopictus cell line was infected with Wolbachia from Aa23 cells and Drosophila simulans (Riverside), resulting in cell lines designated C7-10B and C7-10R, respectively. Characterization via FISH staining showed greater stability and uniformity of Wolbachia infection in C7-10R relative to the infection in C7-10B. Characterization of the Aa23, C7-10B and C7-10R lines is discussed as a tool for the study of Wolbachia-host cell interactions.

Understanding the compensatory responses of crops to pest damage is important in developing pest thresholds. Compensation for pest damage in crops can occur at the plant level, where the architecture, growth dynamics and allocation patterns of damaged plants are altered, allowing them to recover or, at the crop level, where differential damage between plants may alter plant-to-plant interactions. We investigated growth and yield of cotton (Gossypium hirsutum L.) following non-uniform manual defoliation of seedlings. This partially replicates real pest damage and is valuable in understanding crop-level responses to damage because it can be inflicted precisely. Damage distributions included damaging 0, 25, 50, 75 or 100% of the plants. Damage intensity for the damaged plants was varied by removing 100 or 75% of each true leaf when plants had two, four and six true leaves. At the crop level, yield loss increased as the proportion of plants damaged and intensity of damage per damaged plant increased. Neighbour interactions occurred; undamaged plants with damaged neighbours grew larger and yielded better than undamaged plants with undamaged neighbours, while the converse applied for damaged plants with undamaged neighbours. Neighbour interactions were influenced by the intensity of damage and were stronger when 100% of the leaf area was removed than when 75% was removed. At the crop level, when compared with yield estimates based on yield of plants from uniformly damaged or undamaged plots, these interactions resulted in higher yield than expected (+8%). This suggests that damage distribution may have to be considered in studies where artificial or real pest damage is inflicted uniformly on plants.

Forager population sizes of colonies of Coptotermes lacteus(Froggatt) in New South Wales were estimated using two methods: mark–recapture and constant removal, in two disturbed habitats: a pine plantation and cleared farmland. Mark–recapture population estimates were unrealistic and unreliable: they could be improbably large, over 200 million foragers, and they varied enormously between samples for each colony without any pattern. The constant removal population estimates could also be unrealistic: they could be negative or quite different when calculated using regression and maximum likelihood methods. However, the unrealistic results could be predicted reliably, and explained by the lack of re-contact with the sampling devices (bait stations) – a violation of an assumption of the method. This happened more frequently in the plantation than in the farmland, probably because of the greater abundance of alternative food sources in the plantation. Of the two methods, constant removal provided reasonable forager population estimates, relative to direct counts, at least some of the time, plus a mechanism by which reliability could be tested, whereas mark–recapture provided neither. Further refinement and testing of constant removal methods are urged to provide a more reliable population estimation technique for termites.

In the course of a conversation in November 1917, Mr. E. Hutchins, the Chief Veterinary Officer, Uganda Protectorate, drew my attention to an outbreak of rinderpest in the Northern Province of the Protectorate, which first manifested itself in the buffalo of the Chopi Country. The disease was then rapidly spreading through the game in the Glossina morsitans area between Masindi Station and the Kafu River. He pointed out the excellence of the opportunity for investigating the alleged relationship between rinderpest and fly. As I had worked from May till September 1914 in the Northern Province fly belt in association with Mr. W. F. Fiske, I was in a particularly advantageous position to estimate any alteration in the fly distribution which might have occurred as a result of the epidemic. The question had a special local significance, as, should the disease prove fatal to the fly, the introduction of rinderpest among the situtunga on the Islands of Lake Victoria would simultaneously remove the reservoir and the carrier of the mammalian trypanosomes. My release from military duties was duly sanctioned in November 1917, but unfortunate circumstances over which I had no control postponed its fulfilment until April 1918. By this time the disease had almost worked itself out in the fly area, and, what is more to be regretted, the long-deferred rains had commenced throughout the district. The heart of a unique opportunity was thus lost.

Chlorphoxim resistance is found in forest strains of Simulium sanctipauli Vajime & Dunbar, in some areas of the Onchocerciasis Control Programme in West Africa. There is an increase in esterase activity in both adults and larvae in the resistant compared to the susceptible strain with the general esterase substrate 1-naphthyl acetate. This appears to be associated with the temephos and chlorphoxim resistance which are found in the same resistant strain. It is possible that one or more esterases are qualitatively and/or quantitatively changed in the resistant strain compared to the susceptible. Preliminary studies indicated that esteratic hydrolysis and oxidative cleavage were both involved in chlorphoxim metabolism in S. damnosum Theobald sensu latu. There was evidence of an increase in detoxication by both these routes in the resistant compared to the susceptible strain of the cytospecies S. sanctipauli. The increase in oxidative detoxication seen in the resistant strain was associated with a slight, but non-significant increase in cytochrome P450 as measured by the sodium dithionite reduced carbon monoxide difference spectra.

Subterranean termites (Reticulitermes grassei) were surveyed over successive seasons in a managed eucalyptus plantation in southeastern Portugal for 26 months. Termite activity in seven diameter categories of lying dead wood was investigated by a modified line intersection method (LIS). Each item sampled was inspected and assessed for termite attack and for general (i.e. fungal) decay status using standard protocols. Line intersection is quantitative to the extent that it can link foraging and decay parameters to woody biovolume. It was found that termites selected items with larger diameter, the observed trend showing an exponential character with greater termite attack as diameter increased. Attack by termites was positively associated with prior decay by fungi. A clear positive relationship was shown between rainfall and total woody biovolume containing live termites, underlining the importance of moisture for termite activity. Subterranean termites appeared to be important wood decomposers in the woodland studied, with an average of 30% of lying dead wood branches showing signs of termite attack.

The taxonomic status of the Chondrilla gall midge, Cystiphora schmidti (Rübsaamen), is discussed and new generic and specific synonymy is established in the genus Cystiphora. Male, female and larval characters of C. schmidti are described and illustrated on the basis of specimens made available from recent studies of this species in Europe as part of a project to implement biological control of Chondrilla juncea in Australia.

In the absence of insecticide there may be intense selection against alleles conferring insecticide resistance, so that these alleles will decline in frequency. On the other hand, selection will act to favour alleles at modifier loci which cause resistance alleles to become coadapted and increase in fitness even in the absence of insecticide. The relative effectiveness of these two processes is of practical importance and theoretical interest. The fate of polymorphism for malathion resistance was studied in the saw-toothed grain beetle, Oryzaephilus surinamensis (Linnaeus). Five to six lines of each of four strains (8401, 8401sel, 8518B and L1040), each polymorphic for resistance phenotypes, were maintained in insecticide-free culture for up to nine generations, over which period the response of individuals to a discriminating dose of 65 mg m-2 malathion was determined. There was significant reversion to susceptibility in the related strains 8401, 8401se1 and 8518B. Assuming resistance to be primarily controlled by a single major locus, resistant homozygote and heterozygote fitnesses in the absence of insecticide were estimated to be 0.92, 0.83 and 0.68, respectively. The initial frequency of the resistant allele was inversely related to the time since last exposure to insecticide, and also to the fitness of the resistant allele. This could be explained by the selection of modifier alleles that reduce the fitness cost of resistance in the absence of insecticide. In strain L1040 the proportion of resistant individuals actually increased over time (after the second generation) in the absence of insecticide. The fitness of the susceptible allele in this case was 0.83. In all strains there was significant variation among lines in relative fitness and initial resistance allele frequency. Analysis of knockdown proportions revealed highly significant variation between generations that is not easily interpreted in genetic terms but is better explained by limitations of the knockdown bioassay.

All of the pupae, totalling over 3,750, produced by 320 laboratory-bred females of Glossina austeni Newst. allowed to feed from rabbits’ ears, were weighed soon after deposition. Pupal weights were relatively low initially but increased during the first 30 days of the females’ productive life, were high during the next 100 days or so and thereafter declined to less than the initial level.

The effect of density of the Shin-Etsu twist-tie rope pheromone formulation (PBW rope L®) on mating of female pink bollworm, Pectinophora gossypiella(Saunders) was tested in Israel. The success of mating disruption was evaluated during 1997 by the mating table technique, comparing the percentage of mating of virgin sentinel females in pheromone-treated and control plots. Under low pest population pressure application of ‘long-life’ formulation of P. gossypiellapheromone, PBW rope L®, spaced 9 m, 11 m and 14 m apart, resulted in very high suppression of mating (96.5–100%) and complete shut-down of pheromone trap catch. These application rates were much lower than those now prevailing in Israel and elsewhere. Spacing of ropes 20 m apart resulted in less effective mating disruption of 65% only, and shut-down of pheromone traps was also incomplete. The tests during 1998 were carried out at high pest population and efficacy of treatments was assessed by the reduction of male capture in traps in pheromone-treated plots relative to catches in the control. The distance between pheromone sources proved to be the most critical factor determining success. In both years, any spacing significantly greater than 10 m gave markedly less than complete trap catch shutdown/mating suppression. Pheromone dosages and population density were also important in determining mating success. Results obtained in this study indicate the possibility of reducing the number of pheromone sources per unit area and the total amount of pheromone as compared with that in use today, only at very low pest populations. However at high population levels, dispensers closely-spaced, with increased dosages of pheromone, are required.

Orius amnesius sp. n., a predator of Megalurothrips sjostedti (Tryb.) infesting cowpea, is described from the male and female from Nigeria. A sympatric species, Orius albidipennis (Reut.) was also attacking the pest. Wollastoniella gatti sp. n., a predator of tetranychid mites on ornamental species of Solanum, is also described from the male and immature examples from Kenya. O. amnesius resembles O. albidipennis and several other economically important and widely distributed species of Orius found in Africa, Asia and the Pacific.

Glossina, palpalis (R.-D.) was studied in three localities near Voinjama, in a forest region in north-west Liberia, where human trypanosomiasis persists only as sporadic cases. Sites were chosen with different degrees of contact between man, fly and game, in transitional vegetation on the Zeliba River, and in primary forest on the Lofa and Lawa Rivers. The general features, fauna and climate of these areas are described. Catching by nets was found to be preferable to the use of traps. Trap catches averaged about one-quarter of the corresponding net catches. The theoretical basis of ‘animal’ traps is too uncertain for their use in quantitative studies, and under forest conditions there are practical difficulties in siting them in optimum positions; they failed to catch at all at very low fly densities. Heavy rain and the dry season were unfavourable to the fly, particularly outside the forest canopy. A wet-season resting site on horizontal twigs near to the ground is described. The percentage of females in the total catch differed significantly between different habitats, but apparently was not indicative of the degree of hunger in the population. There were no great differences between the sexes in activity patterns, and activity was greatest during the apparently unfavourable climatic conditions of early afternoon. The willingness of the fly to penetrate unfavourable surroundings suggests that the clearing of forest at potential places of transmission is unlikely to afford an effective means of protection. There is some evidence that breeding was curtailed during the rains. Very few engorged flies were found. Fly numbers and distribution were not affected by normal game movements. There is no evidence that the fly was ever dependent on man for food. Where game was driven away the fly tended to follow it. Occasional human foci did not affect the number or distribution of the fly, and fly activity was not correlated with human activity. Intimate and prolonged contact between man and fly did not occur.