A new genus and species of Ichneumonidae, Sliochia bala, reared from a pod husk miner (Acrocercops sp.) of cacao is described and compared with related genera in the Macrini.

Mosquitoes flying at low levels over open farmland were sampled by means of electrical suction traps. These were set up at nine levels from ground level up to 6 m. From the vertical profiles obtained it was possible to recognise three patterns of behaviour: (1) a low-flying group with relatively very high densities below 1 m, comprising Mansonia (Man-sonioides) spp., Aedes spp. and some species of Anopheles; (2) an intermediate group with densities rather evenly distributed at the lower levels but declining above 2–4 m, comprising A. funestus Giles, A. gambiae Giles and Culex neavei Theo.; (3) a high-flying group with catches at 6 m greater, or much greater, than at 1 m, composed of C. antennatus (Becker), C. thalassius Theo. and C. poicilipes (Theo.). For all species, catches after 23.00 h showed an increase in the proportion of mosquitoes taken in traps at the lower levels, this being most marked at ground level and 0·5 m. No influence of either moonlight or wind speed could be detected to account for this. Biting catches on human baits showed a generally similar pattern to suction-trap catches, although differences between baits at 1-m intervals at the higher levels were less than with unbaited traps.

Under simulated natural conditions the anal orifice of the larva of Glossina morsitans morsitans Westw. appears to open either at or soon after parturition. The larva burrows on average within two minutes of deposition; pupariation is completed 10–15 min later. Using methods that prevent burrowing and prolong the crawling period, certain larval movements were related to the pre-pupariation anal discharges and to the rapid spread of the fluid. Although the anus is not generally thought to be connected with the hind gut during the whole of larval life, the presence of uric acid in the discharges indicates that the fluid is a product of Malpighian tubule excretion. In a two-choice chamber in an incubator, flies larviposited significantly more often in the experimental pot if it contained a water- or ether-soluble extract of larval excretion in addition to any pupariating larvae. This points to the presence of a larval phero-mone which may attract gravid females to a breeding site.

Natural populations of four species of the Anopheles gambiae complex occurring in southern Africa were sampled and individuals identified using ovarian polytene chromosomes (19 species A, 190 species B, 140 species C and 54 A. merus Dön.). The genotypes of these same insects were scored for three loci coding for non-specific esterases, and one locus coding for tetrazolium oxidase, after electrophoresis. There is no intra-specific variation at the tetrazolium oxidase locus; species A, B and C share a common allozyme and A. merus is unique. The relative gene frequencies for the 16 allozymes of the three esterase loci for each species give a minimum probability of correct identification of 0·9533 under the worst conditions of sampling, i.e., where samples consist of equal mixtures of species. In practice, resort to such probabilities is necessary only in the discrimination between species A and C. This system of identification is superior to the chromosome method because all adults, whether male or female, and at whatever stage of the gono-tropic cycle, are identifiable.

A light-trap separating hourly catches was operated on a pasture research station in south coastal Queensland for 18 months in 1972 and 1973. A total of 339 000 Noctuid moths was captured. Half of the catch comprised pest species. Weather and nocturnal illumination were recorded on the trapping site. Multiple regression analyses were performed on the raw data, and, for comparison, some pest species were reared under semi-field conditions for a year. Night temperature, night wind and nocturnal illumination, in that order, were the most important factors influencing catch. Temperature and wind were each responsible for about one-fifth of the variance in catch, nocturnal illumination for about one-tenth. Twenty per cent of the variance in catch cannot be ascribed to changes in local weather or illumination. Wind had a significantly stronger influence on males than on females all year round, temperature a significantly stronger one on females than on males in summer. This was probably due to differences in the vertical distribution of flight in the two sexes, females flying lower than males. Nocturnal illumination had a significantly stronger influence on females than on males; on females its influence was almost as strong as that of wind, increasing with rising temperature to be twice as strong in summer as in winter. Females were most abundant in the first part of the night, males in the second. Temperature, wind and moonlight maintain this nocturnal distribution which is probably endogenously controlled. Female flight is probably linked to oviposition, male flight to response to pheromone release from calling females. Heavy out-of-season rainfall had a negative effect on Noctuid populations in the area and strongly increased both larval and adult mortality. Temperatures and rainfall during the larval and adult periods equal to the corresponding long-term averages and totals create optimal conditions for the development of Noctuid populations. Strong indications of migration were found in autumn and spring of 1973. Many moths of different species probably entered the area during nights with wind convergence caused by the passage of cold fronts. Separate analyses on the most abundant pest species confirmed the results of the analyses on the total catch of Noctuids.

The roles of cattle and alternative hosts in maintaining the immature stages of Amblyomma variegatum (F.) and Rhipicephalus appendiculatus Neum. are unknown. Weekly collections of ticks from cattle in two herds in Zambia indicated an apparently higher nymph-adult ratio in the annual totals for A. variegatum than for R. appendiculatus. The larva-nymph ratios for these herds were estimated by a patch-sampling method in which all larvae and nymphs on 100 cm2 areas on the cheek, neck, dewlap, shoulder, ribs, abdomen and lower-foreleg were collected. The overall annual ratios of larvae to nymphs on the two herds were: A. variegatum 5:1 and 14:1, R. appendiculatus 1·5:1 in both herds. The ratios suggest that cattle themselves feed larvae of A. variegatum in sufficient numbers to maintain their nymphal infestation level. The numbers of cattle-fed larvae of R. appendiculatus may not be adequate for this, and alternative hosts may play an important part in maintaining the population at existing levels. There was negligible evidence of significant shift of distribution of the immature stages over the body with advancing season, and it is suggested that patch-sampling affords a method of quantitative comparison of the relative infestations by the immature stages of ticks.

Topical applications of a juvenile hormone (JH) mimic induced and prolonged the mature larval diapause of the southwestern corn borer, Diatraea grandiosella Dyar. The onset of this diapause is marked by an ecdysis from a spotted to an immaculate morph. A high percentage of spotted non-diapause larvae treated with a single dose of a JH mimic moulted into the immaculate morph and became dormant. Similar treatments of diapause larvae led to a reversion to the spotted morph, but the larvae remained dormant. These results imply that diapause larvae contain an intermediate JH titre. A use for JH mimics in disrupting the seasonal phenology of pest insects with larval dormancies is suggested.

A pheromone trap fitted with an automatic recording device to separate hourly catches of males of Phthorimaea operculella (Zell.) is described. Field experiments in Cyprus showed that when the trap was baited with virgin females peak catches occurred shortly before or 1–2 h after sunset; catches increased with wind speed in the range 0·1—4·7 ms-1, decreased with higher relative humidities in the range 62–92%, and were not affected by temperature.

The oligophagy of the African armyworm, Spodoptera exempta (Wlk.), was investigated experimentally. The resistance to feeding on cassava, a non-food plant, declined at a faster rate if the larvae had been reared on artificial diet. If diet-reared larvae were allowed to feed on maize for increasing periods of time the subsequent rejection of cassava increased accordingly. This effect could still be induced after removing the labral or palpal sensilla but not after removing both pairs of stylo-conic sensilla. The left and right pair of styloconic sensilla are supplementary to each other. In so far as aversive responses to non-food plants are concerned, the rearing on artificial diet can be considered as a case of pseudomaxillectomy. It is suggested that during feeding on maize the larva receives a specific input pattern which influences central acceptance-rejection decisions in a time-dependent manner. This specific information is absent from artificial diet and can no longer be perceived by larvae without styloconic sensilla.

The distribution and spread, interrelationship with other animals, and economic importance (mainly domestic) of Anoplolepis longipes (Jerd.) in Mahé, Seychelles, after its accidental introduction about 13 years ago, are described. Temporary control measures based on solid and liquid baits formulated largely from local materials were devised. Baits containing aldrin at 2·5% a.i. and applied at 10 kg (solid) and 20 kg (liquid)/ha decreased the abundance of foragers for about 50 days after treatment. Other insecticides tested were less effective. Bendiocarb (0·04% a.i.) sprayed onto walls of houses and buildings provided protection for about a week outdoors, and for up to two months indoors. There are good prospects for the eventual decline and stability of populations of this ant on Mahé.

To study the effects of plant density on populations of the cabbage root fly (Erioischia brassicae (Bch.) ) and the cabbage stem weevil (Ceutorhynchus quadridens (Panz.)), cauliflowers were planted in 24 concentric circles to achieve spacings of 10–90 cm at 22 plant densities (1·5–83/m2). Some plants were treated with a root drench of chlorfenvinphos. Each week female cabbage root flies laid approximately three times as many eggs per individual plant at the lowest than at the highest plant densities tested. This was equivalent to approximately 350 and 5000 eggs/m2, respectively. The numbers of cabbage root fly pupae produced ranged from 11/m2 at the lowest to 210/m2 at the highest plant density. In the absence of an insecticide, increasing the plant density considerably increased the absolute population of the pest without affecting cauliflower yield. Approximately seven times as many flies were produced per unit area of untreated mini-cauliflowers as from an equivalent area of plants growing at a conventional density. When chlorfenvinphos was not applied, damage by the cabbage stem weevil occurred in 30% and 70% of the plants grown at the lowest and highest densities, respectively.

Experiments were carried out to determine the optimum temperatures and photoperiods for inducing diapause in the cabbage root fly, Erioischia brassicae (Bch.). The induction of diapause occurred at certain receptive stages between the first and third instars of larval development. When developing larvae were subjected to 20±1°C and a 16-h photoperiod for 7–14 days followed by 13±0·5°C and a 10-h photoperiod for 28–35 days, diapause was induced in 84–97% of the pupae; 88–99% of pupae entered diapause when developing larvae were subjected to 13±0·5°C and a 10-h photoperiod for 28–42 days followed by 20±1°C and a 16-h photoperiod for 11–18 days. Similar results were obtained when developing larvae were subjected to 13±0·5°C (day)/7±0·5°C (night) and a 6-h photoperiod. The fecundity of flies from the diapausing pupae was not adversely affected. Application of these results should enable cabbage root fly to be cultured economically for intermittent use.

During 1972–74, 13 865 female mosquitoes of 25 species from eight genera were collected at the Kisumu heronry using light-traps, chicken-baited traps and battery-driven aspirators. A total of 3298 of these were engorged and 2169 were subjected to precipitin testing in order to determine their food sources. A high percentage of feeds on birds was recorded for Coquillettidia karandalaensis (Wolfs) (96%), Culex poicilipes (Theo.) (82%), and C. univittatus gp (65%); Mansonia uniformis (Theo.), M. africana (Theo.) and C. antennatus (Becker) were found to feed on birds occasionally. Results from catches in CDC light-traps set at various heights in trees with nesting birds indicated that C. univittatus gp, C. poicilipes and Aedomyia africana Nev.-Lem. were active in the upper levels of the canopy. Further analysis of blood-meals from birds indicated that C. univittatus gp mosquitoes were feeding principally on ciconiiform birds. Any mosquito which feeds regularly on birds and man must be considered as a potential vector of arboviruses; the results indicate that the most important vectors at Kisumu are probably C. univittatus gp mosquitoes.

Experiments in Malawi showed that the (log) number of males of Diparopsis castanea Hmps. attracted to sex pheromone traps was linearly related to the (log) number of virgin females used as attractant. Virgins remained sexually attractive for up to 31 days but were maximally attractive three nights following emergence; 97·7% of light-trapped females were mated, a small proportion having mated four times. Numbers of matings were directly correlated with temperature at 22.00 h, but relative humidity had little effect. Mean fecundity of mated females was 152 ± 10·3 eggs, multiple mating influencing egg fertility rather than total oviposition. Potential fecundity was linearly related to body weight on emergence. Peak oviposition of unfertilised eggs by virgins occurred at about nine nights following emergence. Of emerging females 2% were barren. Only 1·4% of females mated twice in one night when confined outdoors with males, and there was no difference in the abilities of newly emerged males or males up to four days old to mate with newly emerged females or females up to four days old. Although outdoors males mated on average 0·8 times per night throughout their life, and were capable of mating twice per night, mating propensity of males under laboratory conditions was much lower. Males responded to female sex pheromone throughout the calling period of the female, individuals completing up to 143 orientations during a night without the occurrence of lasting physiological habituation to the pheromone. The importance of this in any control programme aimed at disrupting pheromone communication between the sexes is discussed.

In a series of field trials at Chitedze, Malawi, groundnuts were sown at spacings of 30 cm, 7·5 cm and 2·5 cm within rows 90 cm apart. Contrasting sowing dates were approximately 1 December and 1 January. Immigration of alatae of Aphis craccivora Koch, monitored on observation plots, commenced 5–6 weeks after the emergence of early-sown groundnuts. Numbers of immigrant alatae were significantly greater on late-sown or open-spaced than on early-sown or close-spaced groundnuts, and were correlated with numbers of randomly distributed primary rosette virus infections. During observations, more alatae landed on 56–60-day-old plants than on 85–112-day-old plants. Similar numbers landed on 11–26-day-old plants at 30-cm and 2·5-cm spacing, but significantly more aphids settled on 30-cm spacing. The incubation period of rosette virus was consistently longer in 2·5-cm than in 30-cm spacing, and increased with plant age at inoculation. The virus was transmitted from a low proportion of infected plants before the appearance of rosette symptoms, and from a high proportion of plants snowing symptoms. The rate of spread of virus transmissions from inoculated sources within the crop varied significantly with spacing as 30 cm > 7·5 cm > 2·5 cm. Secondary spread of rosette varied, approximately, with the numbers of aphids per infected plant.

A method is described whereby tsetse visiting a stationary ox can be observed through a one-way glass screen in the presence or absence of man. Under the latter condition six times as many adults of Glossina pallidipes Aust. perch and feed on the ox. In G. morsitans Westw. most flies land in the head-down position and are unaffected by man's presence, but in the absence of man there is a four-fold increase in the number which land and feed in the head-up position. Calculations indicate that in the absence of man virtually all G. pallidipes adults attracted to the ox alight on it, and nearly all attempt to feed. Man's presence not only repels many tsetse completely but also inhibits the landing response of many of those that do approach the ox.

The males of Heliothrips haemorrhoidalis (Bouché) are very rare and the species is thelytokous. Mutation of genes controlling male characteristics will therefore not be subject to selection, and so structural variation in these males is of no taxonomic significance. It is concluded that haemorrhoidalis and ceylonicus Schmutz represent one species in which the females vary in size, sculpture and colour throughout the tropics.

Engorged Culicoides specimens were collected in light-traps from 16 sites in Kenya. The precipitin test was used to identify the blood-meal source of 682 specimens of 21 species over a period of five years. Culicoides pallidipennis C, I. & M. and C. schultzei (End.) were shown to feed mainly on cattle and to a lesser extent on sheep, and thus could be involved in the transmission of bluetongue virus. C. cornutus De Meillon, C. milnei Aust. and C. zuluensis De Meillon are probably not common enough as feeders on cattle and sheep to play more than an incidental role as vectors of bluetongue. C. schultzei is probably also important in the transmission of ephemeral fever. No groups of vertebrates other than Bovidae were implicated as virus reservoirs.