Showing papers in "Bulletin of Entomological Research in 1987"
TL;DR: There is a widely-distributed tobacco-adapted form, closely related to M. persicae but with its own characteristic morphology, which is given the name M. nicotianae sp.
Abstract: Multivariate techniques, principally the method of canonical variates, were used to investigate morphological variation within and between populations of the group of Myzus persicae (Sulzer) from North and South America, Europe, Africa and Asia. The scores on the first canonical variate of samples from tobacco in North America, the Mediterranean region, the Middle East, Africa and Sri Lanka all grouped consistently when compared with samples from other host-plants, even after aphids from tobacco had been reared for up to seven years on a non-tobacco host. Thus there is a widely-distributed tobacco-adapted form, closely related to M. persicae but with its own characteristic morphology. Morphological discriminants are given for the recognition of apterous and alate viviparae of this tobacco form, which is given the name M. nicotianae sp. n. Both M. persicae and M. nicotianae have 2n = 12, and both are frequently heterozygous for apparently the same autosomal translocation, which they must have acquired independently. M. nicotianae is presumably isolated from M. persicae by being permanently parthenogenetic. In Japan and Central Asia, however, aphids of the M. persicae group on tobacco can produce sexual morphs; the taxonomic status of these latter populations is still unclear. Multivariate comparison of European and North American populations of dark green aphids of the M. persicae group with 13 or 14 chromosomes in somatic cell nuclei instead of the normal 12, led to the conclusion that these all belong to one morphologically variable taxon, M. antirrhinii (Macchiati). Keys are provided to the apterous and alate virginoparae of the species of the M. persicae group in America.
141 citations
TL;DR: In a variety of laboratory and field experiments, avermectins have been tested against some 84 species of insects in ten orders, most of which are pests of livestock or horticultural crops or are of general nuisance value.
Abstract: In a variety of laboratory and field experiments, avermectins have been tested against some 84 species of insects in ten orders, most of which are pests of livestock or horticultural crops or are of general nuisance value. This work is reviewed, comparing doses used, methods of application, and responses of the insects. Avermectins (abamectin and ivermectin) are toxic to almost all insects examined, although tolerance varies and death can be uncommonly slow, taking 24 h to 30 days. There is a marked absence of information on physiological processes that are affected by the pesticides, although at the cellular level they are thought to disrupt receptors for y-aminobutyric acid and glutamic acid in the central nervous system and muscular system. At high doses, treated insects are progressively immobilized, and although initially many can move when stimulated, this ability becomes lost. Some show a disturbed water balance and become distended with fluid, while others show disruption of moulting and metamorphosis. Feeding inhibition is commonly observed at sub-lethal doses. Avermectins affect many aspects of reproduction including mating behaviour, egg development, oviposition and egg hatching. The possibility is raised that these diverse disturbances are not all due to disruption of neuromuscular or central nervous system synapses, and the need for work in this area is stressed. Field studies have shown ivermectin to be most valuable in eradicating insect pests of livestock, but the use of abamectin against horticultural pests has produced less impressive results. The limited work on non-target species is discussed, and attention is drawn to some possible environmental consequences of excreted ivermectin on dung-breeding insects.
125 citations
TL;DR: It is shown that scouting for eggs over a limited period of plant development can lead to better timing of spray applications and thus to more cost-effective control measures.
Abstract: New information on the intraseasonal progression of larval infestations of Busseola fusca (Fuller) in South Africa was obtained through repeated sampling in maize plantings of different planting dates over various seasons. Due to the occurrence of distinct periods of moth flight, variation in planting date had a marked influence on levels of larval infestation. Also, plants were found to be most attractive as sites for oviposition between three and five weeks after emergence, resulting in a definite pattern in the time distribution of different larval instars in different plant parts. In the pre-tassel stage of plant development, most larvae occurred in localized groups within the whorls, reaching maximum numbers eight weeks after plant emergence. The emergence of the tassel forced some larvae to migrate to adjacent plants, resulting in an increase of internally damaged plants without an increase in larval numbers. It is shown that scouting for eggs over a limited period of plant development can lead to better timing of spray applications and thus to more cost-effective control measures.
85 citations
TL;DR: Investigation of the migratory flight behaviour of Nilaparvata lugens (Stal), other delphacid and cicadellid pests of rice and some of their heteropteran predators found flight activity in all migrants was found to be very largely confined to periods of about 30 min at dusk and dawn, with minimal activity at other times of the day and night.
Abstract: The migratory flight behaviour of Nilaparvata lugens (Stal), other delphacid and cicadellid pests of rice and some of their heteropteran predators was investigated during the dry-season crop in an irrigated rice-growing area of the Philippines. A combination of radar (including an X-band and a newly-developed Q-band system (8 mm wavelength)), aerial netting, ground trapping and visual observations was used to determine diel changes in aerial density and composition of arthropods in flight over the study site. The most abundant migrant caught in the aerial nets was Cyrtorhinus lividipennis Reuter (a mirid predator of N. lugens), with Nephotettix spp. and Nilaparvata lugens the next most abundant species. Flight activity in all migrants was found to be very largely confined to periods of about 30 min at dusk and dawn, with minimal activity at other times of the day and night. Migration distance in the dusk flight was generally limited to 6–30 km, depending on wind speed, and the dawn migration covered shorter distances due to the lighter winds. Small numbers of rice cicadellids and delphacids including N. lugens were occasionally detected later in the night, and these may have had the potential to migrate longer distances.
83 citations
TL;DR: It is proposed that 2-butanone is an important rendezvous stimulant in nature, bringing the mature male flies into the feeding and oviposition sites (host-trees) of the developing females for mating encounters.
Abstract: Adults of Dacus spp. feed on plant surface bacteria. The responses of D. tryoni (Froggatt) and D. cacuminatus (Hering) to some components of bacterial odours and to cue-lure were tested in a field-cage olfactometer, in studies in south-eastern Queensland. One component of bacterial emission, 2-butanone, attracted D. tryoni (a species responding to cue-lure) but not D. cacuminatus (a species responding to methyl eugenol) and is suggested as the attractive portion of the cue-lure molecule. Sexually mature males and immature females of D. tryoni responded to 2-butanone, cue-lure and bacterial odours in field-cage tests. Females fed on sugar and water required protein hydrolysate to produce eggs, but males were fertile with or without protein. These different nutrient requirements, and the fact that males and females possess different crop colour and bacterial contents when feeding in the same host-plant, indicate that the sexes feed on different substrates. Consequently, the strong bacterial attractant cues in the host-tree may be a feeding attractant to females and a sex attractant to males. It is proposed that 2-butanone is an important rendezvous stimulant in nature, bringing the mature male flies into the feeding and oviposition sites (host-trees) of the developing females for mating encounters.
81 citations
TL;DR: The dynamics of migration of the parasitoids Aphidius spp. between grassland and cereal fields of varying sowing dates was investigated in southern England in 1980 and 1981 as mentioned in this paper.
Abstract: The dynamics of migration of the parasitoids Aphidius spp. between grassland and cereal fields of varying sowing dates was investigated in southern England in 1980 and 1981. Using baffled water traps, direct evidence of migration of A. rhopalosiphi De Stefani Perez females from grassland to winter wheat was obtained in June 1980, suggesting that the early-maturing grassland aphid Metopolophium festucae (Theobald) can act as a reservoir of cereal aphid parasitoids. In 1981, estimates of parasitoid production in cereal fields containing the aphids Sitobion avenae (F.), M. dirhodum (Walker) and Rhopalosiphum padi (L.) were compared with actual numbers to calculate net immigration and emigration. Barley and early-sown wheat (drilled before 14 October) proved to be significant sources of Aphidius spp., with one wheat field generating sufficient parasitoids in May to account for immigration into about 25 late-sown fields. Parasitoid migration as larvae inside aphid alatae was apparently of considerably less significance than that by adults, which were predominantly female. The advantages of early drilling of cereals to form ‘semi perennial’ reservoirs of beneficial insects is discussed and weighed against the corresponding disadvantages, especially an increased risk of barley yellow dwarf virus (BYDV).
59 citations
TL;DR: An identification key to the 22 recognizable species of Cicadulina is given; each species is discussed and illustrated.
Abstract: Leafhoppers of the genus Cicadulina transmit pathogens to Gramineae (including cereals and sugarcane) in Africa, India and South America. Previous taxonomic and applied studies on Cicadulina are reviewed, and an identification key to the 22 recognizable species is given; each species is discussed and illustrated. Two species, C. dabrowskii sp. n. and C. immaculata sp. n., are described; C. anomala Van Rensburg, C. kalaharica Van Rensburg, C. inopia Van Rensburg, C. ungula Van Rensburg, C. bispinosa Van Rensburg, C. opaca Van Rensburg, C. waltersi Van Rensburg, C. scabra Van Rensburg and C. letabae Van Rensburg are established as junior synonyms of C. anestae Van Rensburg, C. bipunctella (Matsumura) as a junior synonym of C. bipunctata (Melichar) and C. triangula Ruppel as a junior synonym of C. storeyi China.
58 citations
TL;DR: An electrophoretic method for the study of enzyme variation, which uses cellulose acetate sheets with an agar overlay for staining and the use of sodium azide as a bacteriocide to allow long term storage of chemicals as solutions are described.
Abstract: An electrophoretic method for the study of enzyme variation, which uses cellulose acetate sheets with an agar overlay for staining, the use of a very good general purpose buffer (citric-aminopropyldiethanol amine) and the use of sodium azide as a bacteriocide to allow long term storage of chemicals as solutions are described. Tests are reported of the technique on Tetranychus urticae Koch, Aedes aegypti (L.) and several species of Drosophila. The results demonstrate that the technique offers sensitivity equal to or greater than starch or polyacrylamide gel electrophoresis and that it is applicable to very small organisms, allowing either the testing of single individuals for large numbers of enzymes or the testing of fewer enzymes under different electrophoretic conditions (i.e. to detect cryptic variation under a single condition). The technique is efficient of time and materials, and safer than conventional methods.
50 citations
TL;DR: In this article, about 130 species of parasitoids and predators are reported, most of them for the first time, to be associated directly or indirectly with the cassava pest Phenacoccus manihoti Matile-Ferrero and its parasitoid, Epidinocarsis lopezi (De Santis), newly introduced into Africa as a biological control agent.
Abstract: About 130 species of parasitoids and predators are reported, most of them for the first time, to be associated directly or indirectly with the cassava pest Phenacoccus manihoti Matile-Ferrero and its parasitoid, Epidinocarsis lopezi (De Santis), newly introduced into Africa as a biological control agent. About 20 species are common. The species are grouped in 11 guilds, which include the indigenous hyperparasitoids, which originally attacked parasitoids of other mealybugs, the predators with which E. lopezi competes for the same food source and their antagonists.
47 citations
TL;DR: Migration and colonization of the coconut palm by Eriophyes guerreronis (Keifer) was studied in St Lucia in the West Indies and increased nut damage appeared to encourage mite migration.
Abstract: Migration and colonization of the coconut palm by Eriophyes guerreronis (Keifer) was studied in St Lucia in the West Indies. Mites were not found in unfertilized flowers but were present within a few weeks of fertilization. Nuts remained vulnerable to colonization for a number of months, and mites were present on nuts for up to 13 months. Protection of nuts for the first few months after fertilization is of most importance. On the tree, much migration could be due to mites walking in large numbers across nut surfaces, and they could move from one inflorescence to another if the two were in contact. Increased nut damage appeared to encourage mite migration.
46 citations
TL;DR: Bed nets are frequently washed in Gambian villages, and this could be a problem in the application of permethrin impregnation of bed nets for vector control, and methods are discussed to overcome this problem at the village level.
Abstract: In a Gambian village, the peak collections of females of the complex of Anopheles gambiae Giles occurred three months after the onset of the heaviest rains; 32% of these were A. melas Theobald, and 54% of blood-meals were identified as originating from man. Counts of A. gambiae s.l. in rooms containing permethrin-treated bed nets were compared with those in rooms containing placebo-treated nets. The numbers in the permethrin-treated nets were far lower than in placebo-treated nets. A higher rate of exophily was noted in rooms containing permethrin-treated nets. The numbers of unfed A. gambiae s.l. found inside the rooms with placebo-treated nets were significantly higher than those with permethrin-treated nets. However, the proportion fed and the mortality in the exit traps were not significantly affected by permethrin treatment. Three-minute bioassays conducted on four different fabric types impregnated at the same concentration showed that the toxicity varied between the fabrics. Handwashing severely reduced the toxicity and approximately halved the permethrin content. Bed nets are frequently washed in Gambian villages, and this could be a problem in the application of permethrin impregnation of bed nets for vector control. Methods are discussed to overcome this problem at the village level.
TL;DR: When the incidence of prolonged flight was measured in moths derived from genetically-matched (full-sib) samples, there was a clear increase in long flights by females derived from the high-density gregaria phase larvae compared with those from solitaria phase larvae.
Abstract: The characteristics of the high and low density forms of noctuid moths, including Spodoptera exempta (Walker), exhibiting a density-dependent phase polyphenism have frequently been discussed in relation to migration. However, the only previous (unpublished) demonstration of an effect of larval phase on adult flight performance, using a tethered-flight technique, was invalidated by the recent discovery that the principal determinant of flight potential in S. exempta is genetic. When the incidence of prolonged flight was measured in moths derived from genetically-matched (full-sib) samples, there was a clear increase in long flights by females derived from the high-density gregaria phase larvae compared with those from solitaria phase larvae. The reasons for the apparent absence of a similar effect in males is not clear, but it is possible that the tethered-flight technique provides a less reliable index of flight capacity in this sex. The characteristics and significance of phase polyphenism in migratory noctuids are discussed. It is suggested that, in S. exempta and possibly some other comparable species, the high-density phase is adapted to accelerate re-dispersal after populations become concentrated, in order to escape the detrimental consequences of high larval densities.
TL;DR: Only a small number of M. persicae genotypes may exist in Britain, as the general lack of qualitative variation at the loci examined is thought to be due to the species having gone through tight population bottlenecks in the past, which have systematically eliminated the rarer alleles, driving the most common to fixation.
Abstract: Electrophoretic variation of eight enzymes (thirteen loci) including esterase-4 (EST-4, the enzyme conferring insecticide resistance) was studied in clones of Myzus persicae (Sulzer) from several localities in south-eastern England (major beet and rape growing areas) and from a site in mid-Scotland (a seed potato growing region). All loci except esterase-1/-2, which showed putative allelic variation with slow (EST-1) and fast (EST-2) bands, and EST-4, which occurred as three principal quantitative variants (susceptible (S), resistant (R1) and highly resistant (R2)), were found to be monomorphic. The occurrence of the insecticide-resistant variants is reported and shown to differ little from previous surveys, with frequencies of R1 aphids on rape in south-eastern England appearing close to fixation (>0·9), probably due to continued insecticide selective pressure. The general lack of qualitative (i.e. mobility) variation at the loci examined is thought to be due to the species having gone through tight population bottlenecks in the past, which have systematically eliminated the rarer alleles, driving the most common to fixation. Consequently, as the data suggest, only a small number of M. persicae genotypes may exist in Britain.
TL;DR: The rate of development, fecundity and lifespan of apterae of Diuraphis noxia (Mordvilko) were determined at five sets of temperature and daylength conditions.
Abstract: The rate of development, fecundity and lifespan of apterae of Diuraphis noxia (Mordvilko) were determined at five sets of temperature and daylength conditions. The time required to complete pre-imaginal growth at mean daily temperatures of 10, 13, 14, 17·25 and 20°C was 19·70, 12·09, 11·25, 9·88 and 8·17 days, respectively. The threshold for development was estimated to be 0·54°C and the number of day-degrees C required to complete development was 158·73.
TL;DR: Differences in glyceride content, preoviposition period, fecundity and lifespan were apparent between laboratory strains, and the implications for migratory flight and reproduction in the field are discussed.
Abstract: Spodoptera exempta (Walker), in common with several noctuid moths, exhibits a density-dependent phase polyphenism. The abdominal glyceride contents of both sexes at emergence were 2·5 to 6·1 times greater in the gregaria than in the solitaria phase moths. Abdominal and thoracic total protein levels, haemolymph total protein, glyceride and carbohydrate, and the relative quantities of tri-, di- and monoglycerides were comparable in the two forms. Weight-related fecundity was strongly influenced by larval phase. Females from solitaria larvae produced approximately half the numbers of eggs laid by those reared in crowded conditions, but this difference was only evident in moths allowed distilled water. Moths having access to sucrose laid comparable numbers of eggs, irrespective of phase. There were no differences in the levels of metabolic reserves in the eggs. Differences in glyceride content, preoviposition period, fecundity and lifespan were apparent between laboratory strains. The implications of these differences for migratory flight and reproduction in the field are discussed.
TL;DR: Feeding was important for adult survival; there was a strong attraction of moths to crops with plentiful honeydew or nectar and a descriptive behavioural model is presented for the first half of adult life, until peak oviposition.
Abstract: Field and cage observations were made on Heliothis armigera (Hubner) in the Sudan Gezira to quantify nocturnal patterns of moth emergence, copulation and oviposition and the ages at which copulation and egg-laying occur. The flight activity pattern of males, virgins and inseminated females was assessed for crops with scarce or abundant sources of honeydew or nectar. A pronounced redistribution of moths between crops during the peak flight activity period (18.15-19.30 h) was demonstrated and measured, with the net exchange being approximately balanced. The direction of this movement was dependent upon the attractiveness of crops for feeding or oviposition. Male and female moths developing from larvae reared on groundnuts had significantly shorter lifespans when fed only water and less fat-body at emergence than moths developing from larvae reared on sorghum. When offered sugar solution, lifespans were significantly greater and differences in the lifespan of moths from groundnuts or sorghum were no longer evident. Adult feeding appears to compensate for any deficiencies associated with a larval diet of groundnut. Feeding was important for adult survival; there was a strong attraction of moths to crops with plentiful honeydew or nectar. A descriptive behavioural model is presented for the first half of adult life, until peak oviposition, and the uses of this model for pest management are discussed.
TL;DR: In this paper, a study of the population ecology and dynamics of Glossina pallidipes Austen in the Lambwe Valley, Kenya was carried out by biconical trap sampling.
Abstract: Investigations into feeding behaviour and activity patterns, basically by biconical trap sampling, were carried out as part of a study of the population ecology and dynamics of Glossina pallidipes Austen in the Lambwe Valley, Kenya. Host-preference determinations from blood-meal analyses showed that over 80% of feeds constantly derived from bushbuck, buffalo and bushpig, in roughly equal proportions. Activity cycles in relation to feeding and pregnancy, investigated by mark-release-recapture and physiological methods, indicated four-day feeding intervals for males and three-day ones for females. The periodicity was more variable in males, and in females was contingent upon reproductive events, with feeding mainly taking place just before the in-utero moult of the second-instar larva to the third instar, just after larviposition and again at a more variable time during pregnancy. Comparisons of nutritional status from size, weight, and fat and haematin levels showed that flies from thicket had consistently greater fat reserves than flies from Acacia woodland and conifer plantation. No seasonal differences were found, nor any relationships between other variables. Based on hourly sample data, both sexes showed unimodal diel activity patterns, but with clear differences. Activity was most closely correlated with temperature, to a lesser extent with saturation deficit and least with light intensity, and better correlations were obtained with females than males. Diel activity patterns in both sexes were also age-related, and from the close similarity found between male and virgin female activity patterns it was inferred that male activity around traps was partly sexually oriented. Using electric screens in conjunction with biconical traps, comparisons between flies attracted to traps and those actually caught showed that traps were relatively more efficient in catching males than females, but captures were representative of the active population in terms of age and pregnancy.
TL;DR: In this article, a field cage in southern England enclosing single rows of potatoes and infested with differing initial proportions of S (susceptible), R1 (moderately insecticide resistant) and R2 (very resistant) clones of Myzus persicae (Sulzer) were sprayed three times, at 14-day intervals, with pirimicarb (carbamate), demeton-S-methyl (organophosphorus) or a mixture of deltamethrin and heptenophos (pyrethroid and organoph
Abstract: Field cages in southern England enclosing single rows of potatoes and infested with differing initial proportions of S (susceptible), R1 (moderately insecticide resistant) and R2 (very resistant) clones of Myzus persicae (Sulzer) were sprayed three times, at 14-day intervals, with pirimicarb (carbamate), demeton-S-methyl (organophosphorus) or a mixture of deltamethrin and heptenophos (pyrethroid and organophosphorus insecticides). The numbers of aphids on top, middle and basal leaves were counted, pre-treatment and one and eight days after each of the three sprays. The resistance genotype frequencies of the three variants were determined by an immunoplate assay which measures the amount of the carboxylesterase E4, the enzyme conferring resistance, in individual aphids. All three chemicals selected strongly for the very resistant variant. After three sprays, R2 aphid frequencies approached or equalled fixation (1·00) for both starting frequencies. However, the deltamethrin-heptenophos mixture selected for R2 aphids more rapidly than the other chemical treatments. Increasing the initial starting frequency of R2 aphids from 0·02 to 0·20 led to a more rapid increase of their frequencies towards 1·00 for all chemicals. The numbers of aphids on all treated plots were less than on the control. However, the more rapid increase in the proportion of R2's on plots treated with deltamethrin plus heptenophos, coupled with enhanced nymph production, resulted in a smaller reduction in numbers than was achieved by the other chemical treatments. The need for novel control methods is discussed in the light of the strong selection for R2 aphids exerted by all three insecticide classes.
TL;DR: The biology of overwintering populations of adults of Culex pipiens L. was studied between October 1977 and April 1980 in southern England showed that there was a rapid build-up at the beginning of hibernation in August, reaching a peak in late October-early November each year and gradually decreasing from December.
Abstract: The biology of overwintering populations of adults of Culex pipiens L. was studied between October 1977 and April 1980 in southern England. Data obtained from population studies showed that there was a rapid build-up at the beginning of hibernation in August, reaching a peak in late October-early November each year and gradually decreasing from December. Extensive movement both in and out and within the hibernation site occurred, with many individuals changing their locations or hibernacula during the course of hibernation. Studies on induced feeding showed that in the early months of hibernation (August-October) exposure to constant light for a minimum period of 12 days was required before the females would take a blood-meal. This period decreased during the course of hibernation. Observations on the physiological condition of hibernating females revealed that up to 90% of the population were inseminated. A few parous females entered hibernation shelters at the onset of winter but did not survive the winter. Furthermore, females used up about 80% of their fat food reserves during hibernation, while there was little or no change in the quantity of glycogen present. From an assessment of the impact of mortality factors on a population of known size, it was observed that exodus from the hibernation shelters accounted for about 30% reduction in the population size while depletion of food reserves and predation by spiders accounted for approximately 15 and 20% mortality, respectively.
TL;DR: Surveying field colonies of C. formosanus confined within baldcypress trees growing in a river in Louisiana found P. grassii was present and an unidentified imperfect species was favourable for the termites and their symbionts, suggesting an important role for microbial modification in termite host selection.
Abstract: In previous laboratory studies, it was demonstrated that baldcypress ( Taxodium distichum ) diets eliminated a critical gut protozoan, Pseudotrichonympha grassii , from Coptotermes formosanus Shiraki. The present authors surveyed field colonies of C. formosanus confined within baldcypress trees growing in a river in Louisiana and found P. grassii was present. Termites inhabiting baldcypress trees preferred pine ( Pinus ) and rejected baldcypress in choice tests in the field. Significantly more termites were recruited to baits when twice as much pine was offered, indicating that C. formosanus adjusted its foraging response to resource amount. In laboratory tests, sound baldcypress sapwood and heartwood depressed survival and gut protozoan counts in C. formosanus , but baldcypress infected with the basidiomycete fungus Rigidoporus sp. and an unidentified imperfect species was favourable for the termites and their symbionts. These results suggest an important role for microbial modification in termite host selection.
TL;DR: The curculionid Cyrtobagous salviniae Calder & Sands and the pyralid Samea multiplicalis Guenee were released in north-eastern Australia for the biological control of the floating fern Salvinia molesta.
Abstract: The curculionid Cyrtobagous salviniae Calder & Sands and the pyralid Samea multiplicalis Guenee were released in north-eastern Australia for the biological control of the floating fern Salvinia molesta. C. salviniae destroyed large areas of weed and was successful at coastal and elevated sites. At equilibrium, there was less than 1 adult/20 plants and only a few, very small plants at each site. The rate at which the weed was controlled varied with mat density. The moth did not reduce plant growth permanently at any site and did not interfere with the performance of the weevil.
TL;DR: Larval activity accentuates the output of attractive volatiles from both xenic and axenic proteinaceous media, possibly due to the effects of digestive enzymes, pH changes, mechanical mixing, warming or aeration or a combination of some or all of these factors.
Abstract: Laboratory bioassays with gravid females of Lucilia cuprina (Wiedemann) were used to isolate the source(s) of olfactory attractants emanating from larvae-infested media. Adults were not attracted by odours from axenic (micro-organism-free) larvae, but volatiles from xenic larvae were highly attractive. The attractants proved to be kairomones not pheromones, as odours from other species of calliphorids and a sarcophagid species were also attractive. Axenic, proteinaceous media produced a low level of attractive volatiles, which was increased by the activities of axenic larvae growing on the media. A greater degree of attraction occurred to odours from xenic media, and this too was much increased by the actions of growing larvae. The order of attractiveness of such volatiles is therefore: xenic with larvae >> xenic without larvae > axenic with larvae > axenic without larvae. It is concluded that larvae-infested media owe their great attractiveness to the volatiles produced by the action of micro-organisms, not to specific larval volatiles. Larval activity accentuates the output of attractive volatiles from both xenic and axenic proteinaceous media, possibly due to the effects of digestive enzymes, pH changes, mechanical mixing, warming or aeration or a combination of some or all of these factors.
TL;DR: Investigation of 16 Scottish clones of Myzus persicae and four of Aulacorthum solani indicated that anholo-and androcyclic clones were predominant, and adults and nymphs of both species survived significantly longer than those of M. solani at this temperature.
Abstract: Investigation of 16 Scottish clones of Myzus persicae (Sulzer) and four of Aulacorthum solani (Kaltenbach) indicated that anholo-and androcyclic clones were predominant. A high incidence of organophosphorus resistance was found in androcyclic clones of M. persicae, but there was no indication of such resistance in A. solani. At 5°C as compared to 20°C, reproduction was decreased and development of nymphs was slower in both species. In addition, the pre-reproductive period and nymphal development time of A. solani were longer than those of M. persicae. Clonal differences in M. persicae at 5°C could not be related to origin, annual cycle or level of organophosphorus resistance, however A. solani clones from the west of Scotland may have been less affected by this temperature than those from the east. The lower limit of reproduction and development in both species was near 2°C. Neither adult survival nor fecundity of clones at this temperature were related to annual cycle, origin or organophosphorus resistance, but anholocyclic M. persicae nymphs survived longer at 2°C than holo- or androcyclic nymphs. A. solani adults survived significantly longer than those of M. persicae. M. persicae survived sub-zero temperatures better than A. solani. In neither species could percentage survival be related to stage of development, gut contents, presence or absence of wings, annual cycle, origin or organophosphorus resistance. Acclimation did, however, increase percentage survival.
TL;DR: Multivariate analyses of four characters from 344 females and seven characters from 90 males show two distinct groups found throughout the Oriental, Pacific and American Regions, corresponding to T. hawaiiensis and T. florum.
Abstract: The significance of morphological variation within the Thrips hawaiiensis (Morgan) species-group is examined. Multivariate analyses of four characters from 344 females and seven characters from 90 males show two distinct groups found throughout the Oriental, Pacific and American Regions, corresponding to T. hawaiiensis and T. florum Schmutz , and an intermediate group, exilicornis Hood, from Africa. The results are compared with previously published morphometric data concerning the separation of T. hawaiiensis and T. florum , and additional distinguishing characteristics are assessed. The distributions of the three forms as recognized in this study are summarized.
TL;DR: Une resistance aux organophosphores est mise en evidence a la fois chez les larves et chez l'animal adulte and est associee a une augmentation de l'activite oxydase.
Abstract: Anopheles subpictus Grassi in Sri Lanka is under selection pressure from both agricultural and public health insecticides. Agricultural selection pressure has produced larval specific carbamate resistance which appears to be correlated with high esterase activity. High esterase activity was found in both larvae and adults, but one of the larval elevated bands was not present in the adult, and two other adult bands were not found in the larvae. Broad spectrum organophosphate resistance was found in both the larvae and the adults and was associated with an increase in mixed-function oxidase activity. There was no evidence of an altered AChE mechanism in this population.
TL;DR: A method of calculating survival rates and population size from mark-recapture experiments for bait-caught haematophagous insects is presented and allows estimates of the population size in addition to the survival and length of the feeding cycle of the mosquitoes.
Abstract: A method of calculating survival rates and population size from mark-recapture experiments for bait-caught haematophagous insects is presented. The method fits the data to a series of simultaneous equations. This procedure is not affected by the cyclical nature of the recapture rate experienced in this type of experiment. Methods are presented which allow estimates of the confidence limits on the estimated parameters. Unlike earlier methods based upon a regression analysis of the log (number recaptured), this method allows estimates of the population size in addition to the survival and length of the feeding cycle of the mosquitoes. The methods have been applied to data collected in Papua New Guinea and give estimates of the total number of Anopheles feeding per night in different villages ranging from 3000 to 46 000.
TL;DR: The biology of the predacious cricket Metioche vittaticollis (Stal) collected from rice in the Philippines was studied in the laboratory and greenhouse and there was no predation on the eggs of Scirpophaga incertulas (Walker).
Abstract: The biology of the predacious cricket Metioche vittaticollis (Stal) collected from rice in the Philippines was studied in the laboratory and greenhouse. The cricket preyed on the eggs of a range of insect pests of rice including Chilo suppressalis (Walker), Cnaphalocrocis medinalis (Guenee), Hydrellia philippina Ferino, Mythimna separata (Walker) and to a lesser extent on the eggs of Leptocorisa oratorius (F.). There was no predation on the eggs of Scirpophaga incertulas (Walker).