Much confusion has arisen in the past with regard to the correct application of the names of certain Pyralid rice borers; I hope the following notes and illustrations will clarify the position.

Sublethal topically applied doses of the carbamate insecticide carbaryl and injection of certain s-triazine chemosterilants to female Diparopsis castanea Hmps. enhanced the rate of oviposition without reducing fertility. Treatment of male moths with carbaryl and certain s-triazines often caused an increase in mating disfunction expressed as an absence of sperm from the spermatheca after an apparently normal mating, permanent copulation or spontaneous extrusion of a spermatophore. No evidencewas found for a direct sterilising action of the chemosterilants against the insect sperm.

Attempts to establish a laboratory colony of Glossina pallidipes Austen from adults and puparia of Uganda origin (Lugala) sent from a colony previously established in Amsterdam have been highly successful. Flies are maintained at 25 ± 0·5°C, L:D 12:12 and 85% RH. They are fed six days per week on whole defibrinated pig blood collected aseptically and irradiated at 1·5 kGy before storage at 4°C. The blood is presented through silicon rubber membranes at 37°C. Virgin female flies are mated when 7–9 days old with equal numbers of 9–12-day-old males in a 30 × 30 × 10-cm cage covered with white Terylene netting and illuminated with a fluorescent light from above, providing 300–500 lux on the cage bottom. The sexes are left together for 40–48 h, during which time they are offered food twice. After separation of the sexes, 30 females are housed in a cage 15 cm in diameter and two males are added. Flies are kept for 90 days before discarding. The establishment of this colony is discussed in terms of the mating behaviour of the species, highlighting differences in the laboratory between G. pallidipes from Uganda and Zimbabwe and between G. pallidipes and G. morsitans morsitans Westwood.

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.

To extrapolate the influence of plant cultivars varying in resistance levels to hosts on parasitoid life history traits, we estimated variation in parasitoid developmental and reproductive performances as a function of resistance in soybean cultivars, which were randomly chosen from a line of resistant genotypes. Our study showed that the parasitoid Meteorus pulchricornis varied widely in offspring survival and lifetime fecundity, but varied slightly in development time and adult body size, in response to the soybean cultivars that varied in resistance to the host Spodoptera litura. Furthermore, the variability in survival and lifetime fecundity was different between attacking the 2nd and the 4th instar host larvae, varying more in survival but less in lifetime fecundity when attacking the 4th than 2nd instar larvae. Our study provides further evidence supporting that plant resistance to herbivorous hosts have variable effects on different life history traits of higher trophic level parasitoids.

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.

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.

The behaviour of Myzus persicae (Sulz.) on plant surfaces treated with emulsions of saturated fatty acids was investigated in three types of test. Aphids showed no clear preferences for settling or larviposition when the acids were applied to whole Chinese cabbage plants or to leaf discs from several different plant species, but settling on halves of Chinese cabbage leaves treated with undecanoic, dodecanoic or heptadecanoic acids was significantly decreased.

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.

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.

Some 246 species of mosquitos are known to occur in Uganda. Of these, 92 (37·4%) have been recorded as breeding in swamps, and the present paper brings together published data and the results of work on the collection and identification of larvae from habitats in a wide variety of types of swamp between 1955 and 1958. Notes on the occurrence and habitats of the larvae are given under each species.

In the present work, only 58 species were found breeding, but these included six new swamp records. Only 26 species appear to breed exclusively in swamps. In addition to the species identified, larvae representing some 14 unrecognised and probably undescribed species were collected. The majority of the swampbreeding species are Culicines, the Anophelines comprising only 21·7 per cent.

The swamp environment in Uganda, with respect to the breeding of mosquitos, is extremely varied. Some possible classifications of the many and various swamps found in the country are given. The distribution of certain species of mosquitos is more or less limited to certain types of swamp This is briefly discussed and examples are given. There is also a definite zonal distribution of some species within a swamp, e.g., Culex (Culex) grahami Theo., C. (C.) guiarti Blanch, and Ficalbia (Ficalbia) malfeyti Newst. occur only in peripheral zones. In general, the interior of the large swamps is unfavourable to the breeding of Anophelines, but Culicines are very abundant there.

Breeding of mosquitos is profoundly affected when swamps are altered by human interference. In certain cases this has resulted in increased production of Anophelines, with the consequent aggravation of the malaria situation.

It is concluded that, from the point of view of human disease, the swamps of Uganda (especially in their natural untouched state) are not as dangerous as previously thought.

Cultivated orchids are the most abundantly attacked by polyphagous mealybugs. This study documented how different density of mealybug Pseudococcus longispinus (Targioni Tozzetti) infestation is associated with a response of antioxidative systems of Phalaenopsis × hybridum ‘Innocence’. The degree of cell damage, estimated by electrolyte leakage measurement and the level of thiobarbituric acid reactive substances (TBARS), the content of pigments as well as the activity of antioxidative enzymes and proline level, as measurements of stress and stress compensation in moth orchid were examined. The highest electrolyte leakage (EL) value among samples from colonized plants was found in the orchids from series III (50 individuals/plant), whereas the lowest in the plants from series II (20 individuals/plant). The TBARS content reached the highest level at the lowest number of feeding insects (series I). Peroxidase activity toward guaiacol was significantly increased in series I (5 individuals/plant). The highest catalase activity was recorded in plants colonized by the highest number of scale insects (series III). Whereas, the highest value of proline was in series II. The content of individual photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) in plant tissues did not vary significantly between control and colonized orchids. The results have not confirmed hypothesis that the increasing number of mealybugs occurring on plant enhanced plant physiological response. The degree of longtailed mealybug infestation on plants was positively correlated only with electrolyte leakage and catalase activity in leaf tissues.

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.

At the suggestion of Mr. S. A. Neave, I have prepared the following brief notes of my observations on the changes in the distribution of Glossina morsitans within the Lundazi District.

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.

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 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.

The study aimed to quantify the influence of common plant polyamines and tyramine on probing behaviour in the bird cherry-oat aphid (Rhopalosiphum padi L.). Electrical penetration graphs (DC) were used to monitor the probing and feeding behaviour of R. padi exposed to the amines agmatine, cadaverine, putrescine, spermidine, spermine and tyramine. The study results showed that the analyzed amines tended to shorten the stylet activity of aphids in the gels (as indicated by the g-C pattern), prolong the duration of non-probing behaviour (g-np pattern) and decrease salivation into the gels (g-E1pattern) and ingestion from the gels (g-G pattern). The 10 mM concentration of the studied amines, especially cadaverine, reduced or completely inhibited aphid ingestion. The obtained results demonstrate that plant amines participate in plant defence responses to R. padi through disturbance of its probing behaviour and the intensity of such effects is concentration dependent.

An experiment on Geescroft field, Rothamsted, from 1951 to 1954, tested the direct and residual effects of BHC, DDT, aldrin and chlordane applied to control wireworms (Agriotes spp.) in wheat.

The treatments applied were BHC seed dressing at 2 oz./bushel of a dressing containing 20 per cent. γ isomer of BHC; BHC 3·5 per cent. dust, combine-drilled to give 3·8–4·0 oz. γ isomer per acre; DDT 5 per cent. dust, combine-drilled to give 7·5 lb./acre technical DDT; aldrin 1·78 per cent. dust, combine-drilled to give 3·56 lb./acre technical aldrin, and chlordane 5 per cent. dust, combine-drilled to give 5 lb./acre chlordane.

In the year of application, the first out of old grass, when wireworm attack was slight, the plots treated with BHC, aldrin and chlordane, combine-drilled, gave significantly greater yields than the control plots. In the following year, when wireworm attack was heavier, residual effects on yield were observed on plots initially treated with BHC, DDT, aldrin and chlordane, combine-drilled. In the third year, residual effects on yield were observed on the plots initially treated with BHC, aldrin and chlordane, combine-drilled.

No direct or residual effect of BHC seed dressing was observed.

The residual effects are closely associated with the effect of the treatments on the wireworm population.

The results are compared with those of previous experiments and the increases in yield from the various treatments are discussed briefly.

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.