Predatory arthropods on cabbage terraces were studied by square flooding and by pitfall trapping in January 1992, following a transect through the Cordillera Region of Luzon, with decreasing numbers of insecticidal sprays per year. Predator numbers were sampled along this transect per 4 m2 and with 15 pitfall traps per site. The dry biomass of predators was also measured. The four sites studied were classified as two pairs, one with high input of insecticides and low predator numbers, low biomass and diversity, the other with low insecticidal input and high predator numbers, high biomass and diversity. The number of ant (Hymenoptera: Formicidae) genera per 15 pitfall traps increased along the transect, showing that ants might be used as indicators of the insecticidal intensity for growing vegetables in the Luzon Cordillera Region. Compared with Europe, the potential abundance and diversity of predators in the Philippines proved to be very high. The reasons for the large differences between sites concerning abundance and diversity of predators are discussed, together with conclusions drawn from the findings presented.

A summary is made of the literature dealing with the bionomics of Aphomia gularis (Zell.), a storage pest of almonds, walnuts, groundnuts and prunes, and to a lesser extent of rice and grain. Additional information is also given on its habits and occurrence in Britain.

An outline is given of its origins, introduction and establishment in various parts of the world. The evidence leaves little doubt that the species originated in south-east Asia, its occurrence elsewhere being, with few exceptions, confined to the major ports of western Europe and North America. Cases of the spread of the pest from south-east Asia can be traced to the export of infested goods from that area. Unless action is taken to prevent further dispersal and measures applied to wipe out the known centres of infestation, further establishment of this species can be expected in countries at present not affected.

It would appear that A. gularis is a subtropical and warm-temperate species, rarely found in the tropics and only able to maintain itself towards the northerly limits of its range, as in northern Britain and Sweden, in heated premises. In the cooler temperate regions, such as Britain, it cannot compete with such species as Ephestia elutella (Hb.) while in the tropics its ecological niche is filled by the very closely related species Corcyra cephalonica (Stnt.).

Its apparent absence from regions in the southern hemisphere, where conditions favourable for development exist, may be due to its presence not having yet been recognised.

The common Egyptian Trogoderma, T. afrum Priesner, is compared morphologically with the widespread T. granarium Everts and found to be almost identical. The two interbreed and are therefore considered to be conspecific. The morphological differences between T. granarium and T. versicolor (Creutz.) are described. These species do not interbreed.

Field studies were carried out between 1974 and 1978 on the hispine Uroplata lantanae Buzzi & Winder which feeds on Lantana tiliaefolia plants under shade in temperate climate areas of Paraná State, southern Brazil. The life-cycle from egg to adult took 48–54 days between October and January with only one generation a year. Adults fed by rasping leaves and larvae mined leaves, occasionally destroying up to 24% on individual plants. Adults colonised tall plants preferentially and chose to oviposit on the higher branches, which suffered significantly less leaf abscission. Greater numbers of all stages of the hispine were found on lantana plants around which a plant-free zone was created compared with those growing amongst other understorey plants. Larvae were parasitised by a complex of braconid, eulophid, chalcid and torymid parasitoids, with greater parasitisation occurring at lower branch heights. Multiple-choice host-specificity tests and field observations showed that U. lantanae fed only on L. tiliaefolia and L. camara. The effectiveness of U. lantanae as a biological control agent of lantana in Australia is discussed.

During the past few months a large amount of Coccid material has been submitted to me for identification through the Imperial Bureau of Entomology. A large proportion of the species came from Uganda where they were collected by the Government Entomologist, Mr. C. C. Gowdey ; smaller collections were also received from other parts of Africa, including Zanzibar ; and from Barbados from Mr. John R. Bovell, Superintendent of Agriculture. Nearly all of the new species which have so far come to hand are described in this paper ; and records and descriptions of other species are also given where it has been thought desirable to do so.

A rickettsia-free (aposymbiotic) stock of Aedes polynesiensis Marks (POLY-A) was crossed with (a) three symbiont-infected stocks of A. polynesiensis (POLY-S from Samoa and POLY-N and POLY-T from Fiji), (b) A. pseudoscutellaris (Theo.) (PSE) from Fiji, (c) A. alcasidi Huang (ALC), A. scutellaris katherinensis Woodhill (KATH), A. s. malayensis Colless (MAL) and A. s. scutellaris (Wlk.) (SCUT), which occur to the west of Fiji and (d) an aposymbiotic stock of A. cooki Belkin (CO) from Niue. It was bidirectionally compatible with CO, but in all other crosses compatibility was high when POLY-A was the male parent and very low when it was the female parent. Backcross data suggested that the crossing type was maternally inherited. ALC and KATH were bidirectionally compatible; both were virtually incompatible with POLY-S and PSE, compatible with SCUT when the latter was the female parent, and compatible with CO when the latter was the male parent. POLY-S females were moderately compatible with a third Fijian stock of A. polynesiensis (POLY-V), and POLY-N and POLY-V were compatible with PSE. If, as in Culex pipiens L., rickettsia-like symbionts are responsible for cytoplasmic incompatibility, then aposymbiotic males should cross successfully with symbiont-infected females, whereas the reciprocal cross should be unsuccessful. Since PSE, MAL and SCUT contain symbionts, their crossing relationships are consistent with the hypothesis. However, ALC and KATH appear to be aposymbiotic and their crossing relationships conflict with the hypothesis. There is little evidence of behavioural barriers to mating between species, but whereas male hybrids of two eastern species were capable of normal insemination, male hybrids between western and eastern species gave very low insemination rates. The egg-hatch rates from backcrosses of female hybrids between western and eastern species to the parents were reduced.

Field sampling of grasses growing in and near rice fields at 12 sites in Nigeria during April/May 1994 recorded the presence of galls on Paspalum scrobiculatumat densities of up to 10.9 galls per m2. These galls were induced by Orseolia bonzii Harris, sp. n., which is described. This species is morphologically close to, but distinct from, the African rice gall midge, Orseolia oryzivora Harris & Gagné, with which it has been confused in earlier studies of that pest species. In host-transfer experiments O. bonzii did not transfer to rice, Oryza sativa. Six hymenopterous parasitoids were reared from galls of O. bonzii and the most abundant of these were Platygaster diplosisae Risbec, Aprostocetus nr. procerae (Risbec) and Neanastatusnr. cinctiventris Girault. Host-transfer experiments with the Platygasterand Aprostocetus species from O. bonzii on Paspalum indicated that the Platygaster may not transfer onto O. oryzivora on rice whereas the Aprostocetus does. The overlap between the parasitoid faunas of the two species of Orseolia is potentially useful as it may be possible to enhance the natural biological control of O. oryzivora by manipulating parasitoid populations on Paspalum.

Insects migrating over two sites in southern UK (Malvern in Worcestershire, and Harpenden in Hertfordshire) have been monitored continuously with nutating vertical-looking radars (VLRs) equipped with powerful control and analysis software. These observations make possible, for the first time, a systematic investigation of the vertical distribution of insect aerial density in the atmosphere, over temporal scales ranging from the short (instantaneous vertical profiles updated every 15 min) to the very long (profiles aggregated over whole seasons or even years). In the present paper, an outline is given of some general features of insect stratification as revealed by the radars, followed by a description of occasions during warm nights in the summer months when intense insect layers developed. Some of these nocturnal layers were due to the insects flying preferentially at the top of strong surface temperature inversions, and in other cases, layering was associated with higher-altitude temperature maxima, such as those due to subsidence inversions. The layers were formed from insects of a great variety of sizes, but peaks in the mass distributions pointed to a preponderance of medium-sized noctuid moths on certain occasions.

Emergence and life-span of wheat bulb fly, Leptohylemyia coarctata (Fall.), have been studied by the use of a field-cage-marking technique. Emergence was investigated by observing the numbers of flies emerging daily from an area of infested wheat enclosed by a cage of fine mosquito-netting, and life-span by making a daily census of marked and individually recognisable flies which had been liberated in the cage. Flies were handled only when being marked and in the later part of the work all observations were made without touching either them or the wheat.

Flies were chilled to render them comatose for marking and under certain circumstances this and the marking was-harmful. Attempts were made to reduce these harmful effects.

Emergence dates varied from year to year depending on the temperatures of spring and early summer, and there were also considerable differences between the emergence dates of populations of adjacent fields in the same year. Consistently, males appeared before females.

The ratio of the number of flies seen to the number known to be alive on each day varied according to weather, flies being more difficult to find on windy days than on calm ones and on bright days than on dull ones.

The observed life-spans of both sexes varied greatly, up to a maximum of 75 days for females and 55 days for males. An exact statement of mean life-span was not possible because there was a tendency for flies emerging later in the season to be less long-lived than those emerging earlier. Most flies of both sexes lived for over 30 days.

The observed life-spans fall short of the true life-spans by amounts that depend on the proportions of living flies seen each day. Two methods are shown by which the mean unrecorded life-span can be calculated.

The humidity responses of Trogoderma granarium Events were tested in humidity gradients set up in choice-chambers, each comprising a petri-dish with the lower half divided diametrically into two compartments containing sulphuric-acid soluctions affording different relative humidities and surmounted by a copper-gauze platform on which the insects, released centrally, could move about. Counts of the numbers in either half of the arena were made at 15–minute intervals over two hours.

In a gradient of 20–80 per cent. relative humidity, at 20°C., the average count was significantly greater on the drier side than on the moister one for larvae and adults tested in groups and for larvae and adult males, but not females, tested singly; the response was greater when the insects were tested in groups. Antennectomised adults, tested at 25°C. in a gradient of 20–100 per cent. relative humidity, showed no response, although intact control beetles showed a significant perference for the drier side. When adults were tested in groups at 25°C. in a range of gradients, from 20–10 to 20–100 per cent, a preference for the drier side was invariably shown, the response tending to be greater and to occur more rapidly in larvae than in adults, and as the humidity gradient steepened.

Trials were carried out from 1958 to 1961 at Fassouri Plantation in Cyprus to assess the value of dimethoate (0,0-dimethyl S-methylcarbamoylmethyl phosphorodithioate) against California red scale, Aonidiella aurantii (Mask.), on orange, lemon and grapefruit trees. This pest has hitherto been controlled in Citrus plantations by annual programmes of sprays containing parathion, malathion or white mineral oil, singly or in combination.

Sprays were applied to Citrus trees at high pressure by means of hand-lance or motor-driven equipment in such a way that all parts of the tree were thoroughly wetted. Treatments were replicated in Latin square experimental designs. Results were assessed by counting the numbers of scales on samples of leaves, fruits, twigs and bark taken at various intervals after spraying and also, in some trials, before spraying. The earlier trials were concerned with the numbers of scales killed after single applications and the later trials with the level of control resulting from full seasonal spraying programmes.

A preliminary trial in 1958 showed that very high kill of the scale was produced by a spray containing 0·2 per cent, of dimethoate. In 1959 a range of concentrations from 0·01 to 0·15 per cent, was compared with the standard parathion/malathion mixture against the scale on orange and lemon trees. At 0·03 to 0·06 per cent., dimethoate gave a level of control equal to that of the standard spray and at higher concentrations it was superior to the standard. This superiority was confirmed in trials carried out during 1960 using dimethoate concentrations from 0·06 to 0·1 per cent., the observations being extended to include immature stages of the scale. A high kill of all developmental stages was produced by all the concentrations used, and at 0·08 to 0·1 per cent, dimethoate gave higher kills than the standard spraying mixture.

The effect of dimethoate against late-season infestations of fruits was next investigated, using mixtures with white mineral oil as well as dimethoate alone. Standard late-season sprays of mineral oil with or without parathion were included for comparison. Dimethoate alone at 0·08 per cent., or at 0·05 per cent, with 1·0 per cent, mineral oil, gave good control of the scale, on fruit. Both these sprays were superior, to the standard oil or parathion/oil mixtures. The results suggest that dimethoate may be especially valuable against scale on full-sized fruits, the control of which has hitherto been difficult.

During 1961, full seasonal spraying programmes with the standard compounds were compared with others using dimethoate at concentrations suggested by the earlier trials. The treated plots were large and the spraying methods approximated to normal estate practice. The final results were based on the level of infestation of fruits at harvest, and comparisons between standard and dimethoate programmes were made by means of Ebeling's corrected relative infestation index (C.R.I.). Values of the C.R.I, below 100 indicate that the degree of control achieved by the standard has been exceeded by the test spray. In the first trial, where early-season infestation was not heavy, the standard programme consisted of an initial parathion/malathion spray followed later by an application of white oil, and the test programmes comprised sprays of dimethoate at 0·04 or 0·06 per cent., both followed by white oil, or 0·08 or 0·1 per cent, without a second treatment. The C.R.I, values from these four programmes were 24, 22, 58 and 7, respectively, showing that all were better than the standard. The second trial was carried out in a plantation with a heavy early-season infestation of the scale; the same standard programme was compared with dimethoate sprays at 0·04 and 0·08 per cent., both followed by white oil. The C.R.I. values for these two programmes were 144 and 36, respectively. In the third trial single seasonal applications were compared, using a spray containing 1·5 per cent, white oil as the standard. The four test sprays comprised white oil 1·5 per cent, plus malathioii 0·05 per cent., white oil 1.0 per cent, plus dimethoate 0·04 per cent., dimethoate 0·04 per cent., and dimethoate 0·08 per cent. The respective C.R.I, values of the test sprays were 68, 38, 56 and 29.

In trials against other pests of Citrus trees dimethoate gave control of Coccus hesperidum L. at concentrations of 0·04 and 0·08 per cent. It was effective against Aceria sheldoni (Ewing) at concentrations of 0·08, 0·04 and 0·02 per cent., but was found to be ineffective against Phyllocoptruta olcivora (Ashm.).

During the trials a number of different formulations were used, including miscible oils and wettable powders. One of the miscible oils caused severe scorch marks on fruits; this was shown to be due to the formulating materials and not to dimethoate. A certain amount of leaf-drop was noticed in some trials, and this requires further investigation. Dimethoate is a comparatively safe compound from the point of view of hazards to operators, and toxic residues in sampled fruit have been found to lie within the limits that have been suggested as safe.

The principal conclusion from these trials was that dimethoate is a valuable addition to the limited range of insecticides available for use against Aonidiella aurantii. At fairly high concentrations (0·08%) it gives better control than spray mixtures in current use, and this suggests that it may be possible to devise programmes giving satisfactory control with fewer applications. At lower concentrations (0·04%) it is about as effective as present insecticides. Although dimethoate is both a contact and systemic insecticide, observations suggested that the former function was mainly involved in its action against this scale.

The status of the different cytological variants of Simuliumsanctipaulisensu stricto Vajime & Dunbar (sensu b8Post, 1986) found in Ghana and Côte d’Ivoire is cytotaxonomically evaluated in view of recent revisions of the S. sanctipauli subcomplex. Three geographical variants designated as ‘Pra’, ‘Comoé’ and ‘Sassandra’forms of S. sanctipauli are described. The ‘Pra’ form is genetically differentiated from the other two forms by a distinct sex-determining system. The ‘Comoé’ and ‘Sassandra’ forms are considered as the two ends of an interspecific stepped cline with the River Bandama basin as the zone of contact. The possibility that the ‘Comoé’ form populations breeding in southwestern Ghana could serve as reinvading S. sanctipauliinto the Onchocerciasis Control Programme (OCP) area in West Africa is discussed.

Three French strains of Culex pipiens L. were compared at the fourth larval instar for tolerance to organophosphate and carbamate insecticides, with and without the addition of synergists (the oxidase inhibitors piperonyl butoxide and CGA 84708) (a propynyl compound) and the carboxylesterase inhibitors triphenyl phosphate (TPP) and S,S,S-tributyl phosphorotrithioate (TBPT). The S54 strain was resistant to all the organophosphates tested (chlorpyrifos, malathion, monocrotophos and profenofos) compared to the susceptible LA VIS strain but only slightly tolerant to the two carbamates (carbaryl and naphthyl phenylcarbamate). The MAURIN strain was resistant to all the insecticides, including the carbamates, at a higher level. The action of chlorpyrifos and malathion on S54 was very strongly synergised by TBPT, less strongly by TPP and not at all by piperonyl butoxide. In fact, resistance was enhanced by piperonyl butoxide, as was resistance to monocrotophos and profenofos by CGA 84708. No synergist had much effect on the MAURIN strain, although TPP slightly increased the toxicity of malathion, and piperonyl butoxide and CGA 84708 slightly increased the toxicity of carbaryl. The toxic effect of carbaryl was also increased by the addition of extra acetone. Electrophoretic studies showed that the carboxylesterase enzyme coded by gene Est-20.64 (which is in linkage disequilibrium withEst-3A and acts as a marker for it) was absent from LA VIS but present in the resistant strains; but, whereas S54 was monomorphic for the gene, MAURIN was polymorphic (frequency 0·5). It is concluded that organophosphate resistance in S54 was due to detoxification by carboxylesterase wherease organophosphate and carbamate resistance in MAURIN had a strong non-metabolic component, possibly an insensitive acetylcholinesterase.

Dr. Andrew Balfour, Director of the Wellcome Bureau of Scientific Research, has submitted to the writer for study part of the Diptera collected on his recent voyage in the American tropics. A species of Simulium from the valley of the Atrato River in Colombia proves to be new and is described below. Through the good offices of Dr. Balfour further interesting material was received from K. S. Wise, Surgeon-General for British Guiana, and from F. W. Urich, Entomologist of Trinidad. These lots contained an additional new species of Simulium each, of which the descriptions follow. Diptera belonging to other groups and of economic interest will be treated in subsequent papers.

The feeding responses, growth and population development of Nilaparvata lugens (Stål) are quantified on a range of twelve susceptible or resistant host-plants. Paris of rice varieties carrying the Bph1, bph2 and Bph3 resistance genes are compared as hosts for N. lugens, and it is concluded that such notations do not adequately describe the diversity of plant resistance mechanisms. Evidence is presented for resistance mechanisms involving enhanced insect activity and gustatory responses to unacceptable phloem.

A significant effect of moon phase on light-trap catches of Anopheles species was observed during a longitudinal study carried out in a forested belt of Madhya Pradesh, India, inhabited by tribal people. However, moon phase does not seem to have any effect on the proportion of adult Anopheles culicifacies Giles in the total catch, or the parity rate in this species, which is the vector responsible for perennial transmission of malaria in the area.

This paper deals with Glossina pallidipes, G. austeni and G. brevipalpis as they occur on the Kenya coast.

Temperature and saturation deficiency both exert a generally inverse effect on the activity and apparent density of both G. pallidipes and G. austeni. True density also varies inversely as the s.d.

Several aspects of the biology of Xylotrechus arvicola (Olivier), an emerging grape pest, were studied under laboratory conditions. Four diets were tested to rear this species in the laboratory. Among them, only one made rearing from larva to adult possible. The highest mortality, in all cases, was recorded during the first days of larval development. Larvae were kept 45 days at 8°C to break diapause in order to reduce the normal field larval developmental time. The species' developmental time was similar between sexes, while pupal developmental time and weight were significantly greater for females than for males. As part of a complementary study, life table parameters of females obtained from the larvae reared on the artificial diet were compared to those of females emerged from field-infested grape root wood. Both laid the majority of eggs in the first two weeks after emergence, and they had a similar pre-laying period. Nevertheless, the females from the diet-reared larvae lived significantly longer, laid eggs over a longer period of time and showed higher fertility than those emerging from infested grape root, suggesting that diet fulfils larval nutritional needs. The species’ laboratory-reared population exhibited a low intrinsic growth rate value (rm=0.01) as a result of its long egg-to-adult developmental time and its high larval mortality.

Infection of Lacanobia oleracea(Linnaeus) larvae with the microsporidium Vairimorpha necatrix(Kramer) resulted in significant effects on the survival and development of the braconid parasitoid, Meteorus gyrator(Thunberg). Female M. gyrator did not show any avoidance of V. necatrix-infected hosts when they were selecting hosts for oviposition. When parasitism occurred at the same time as infection by the pathogen, or up to four days later, no significant detrimental effects on the parasitoid were observed. However, when parasitism occurred six to eight days after infection, a greater proportion(12.5–14%) of hosts died before parasitoid larvae egressed. Successful eclosion of adult wasps was also reduced. When parasitism and infection were concurrent, parasitoid larval development was significantly faster in infected hosts, and cocoons were significantly heavier. However, as the time interval between infection and parasitism increased, parasitoid larval development was significantly extended by up to two days, and the cocoons formed were significantly (c. 20%) smaller. Vairimorpha necatrix spores were ingested by the developing parasitoid larvae, accumulated in the occluded midgut, and were excreted in the meconium upon pupation.

Lysinibacillus sphaericus (Bacillales: Planococcaceae) is a spore-forming bacillus used for the biological control of mosquitoes (Diptera: Culicidae) due to its larvicidal activity determined by various toxins and S-layer protein produced either during sporulation or by the vegetative cell. Aedes aegypti and Culex quinquefasciatus are the vectors of arboviruses that cause tropical diseases representing a current public health problem. Both species may coexist in the same larval development sites and are susceptible to the larvicidal activity of L. sphaericus. In this study, we compared the larvicidal effects of L. sphaericus 2362 (WHO Reference strain) and native strains III(3)7 and OT4b.25 against Cx. quinquefasciatus and Ae. aegypti in single-species and mixed-culture bioassays. Findings showed that L. sphaericus spores, vegetative cells and a combination thereof possessed high larvicidal activity against Cx. quinquefasciatus larvae, whereas only the formulation of L. sphaericus vegetative cells was effective against Ae. aegypti larvae. Similar results were obtained for field-collected larvae. We propose that a formulation of vegetative cells of L. sphaericus 2362 or III(3)7 could be a good alternative to chemical insecticides for the in situ control of mixed populations of Ae. aegypti and Cx. quinquefasciatus.