A comparison was made of the efficiencies of catching parties with hand nets and electric back-pack and screen traps for the capture of Glossina palpalis palpalis (R.-D.) and G. tachinoides Westw. in northern Nigeria. Whilst there was little to choose between the various devices during standing catches, one electric back-pack caught up to four times as many G. palpalis as two men with hand nets during moving catches on fly-rounds. Two reasons for the observed variation in success rate of the catching party with hand nets are suggested, and estimates are made of the relative efficiencies of each method at capturing flies during a single traverse of a fly-round. The combined use of the electric back-pack and screen drawn immediately behind the back-pack wearer recorded the arrival height of the flies, whilst hand-net catches tended to reflect the heights at which the flies spent most of their time after arrival. There were differences between the sexes both in arrival height, perhaps related to differences in resting heights on the vegetation, and in the fat and haematin levels of flies caught in hand nets above and below the waist. High ambient temperature reduced the average height of the visits of both sexes to human bait. The relevance of the results obtained in this study to sampling tsets populations is discussed in relation to various seasonal changes in hand-net samples recorded in the literature.

Myzodes, Mordv., 1914, type Myzodes tabaci, Mordv. (═ Aphis persicae, Sulzer) is a synonym of Nectarosiphon Schouteden, 1901 (nom. nov. for Macrosiphum, Del Guercio, 1900, nec Passerini, 1860). Following Baker's 1920 Generic Classification, Aphis convolvuli, Kalt. (which clearly is Aphis persicae, Sulzer) is the type of Macrosiphum, Del Guercio, and therefore of Nectarosiphon Schouteden, a subgenus of Myzus, Pass.

When larvae of Pieris brassicae (L.) were fed on leaves of plants showing symptoms of deficiency of nitrogen, phosphorus, potassium or iron, some or all of the following effects were recorded in each experiment: —

Reduction of larval weight (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).

Reduction of relative growth rate (deficiency of (1) N throughout larval life, (2) Fe from time of hatching, from sixth day and for last two larval instars).

Increased larval mortality (deficiency of N, Fe from time of hatching).

Delayed pupation (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).

The more detailed experiments with iron-deficient diet showed that similar effects were produced at whatever stage of larval development it was first supplied.

Larvae fed on iron-deficient leaves from the time of hatching appeared to have received a severe initial check to growth, but this was followed by some degree of recovery so that they showed a higher relative growth rate, a few days later, than larvae given the same diet six days after hatching.

Preliminary trials were made on the effects of the addition to diets of iron-deficient leaves of various nutrient substances sprayed on to them. No markedly beneficial results were noted.

In experiments with Aëdes aegypti (L.), fourth-stage larvae bred at 30°C. survived exposure to 0·5°C. for 7 hours, but none recovered after exposure for 17 hours, although nearly all those from the same culture that had been acclimatized for one hour to 18 or 20°C. did so. No such effect followed acclimatization at 10°C., at which larvae are in chill coma. Larvae acclimatized at 18°C. survived exposure to 5°C. for longer than did those from 30°C. Earlier work showed that the thermal death point, for a one-hour exposure, was 42°C. for larvae acclimatized at 30°C. but rose to 44°C. for larvae acclimatized to 37°C. It is concluded that the effects of high or low extremes of temperature may be substantially modified by a brief period of acclimatization at a less extreme temperature.

Fopius arisanus is a solitary egg–pupal endoparasitoid that attacks several species of tephritid fruit flies, particularly Bactrocera spp. This species, indigenous from the Indo-Australian region, was introduced into Mexico for biological control purposes. From the standpoint of the ‘new associations’ concept this parasitoid has been evaluated against fruit flies in the Anastrepha complex. We investigated the specificity of F. arisanus responses to fruits infested with two species of Anastrepha. We examined whether fruit volatiles attractive to this parasitoid are induced as a result of fruit fly oviposition. We also investigated whether F. arisanus females are able to discriminate between the oviposition-induced volatiles from host eggs parasitised by conspecifics and volatiles from unparasitised eggs. All experiments were performed in a wind tunnel. Results showed that mango fruits infested with A. ludens eggs (2–3 days after egg deposition) were significantly more attractive to naïve F. arisanus females compared with non-infested fruits or fruits infested with larvae. In addition, guava fruits harbouring A. striata eggs were significantly more attractive to the parasitoid than non-infested fruits or fruits infested with larvae. Thus, the parasitoid was attracted to fruits with eggs, but fruit and fly species did not influence the parasitoid attraction. We also found that F. arisanus females were more attracted to fruits exposed to fertile A. ludens females (i.e. fruits with eggs inside) compared with fruits exposed to sterile females (i.e. fruits with no eggs inside) or fruits with mechanical damage. Parasitoid females were not attracted to A. ludens eggs. The results suggest that the presence of eggs induces volatiles that attract parasitoids. Finally, we found that F. arisanus was able to discriminate between fruits with unparasitised eggs vs. eggs parasitised by conspecifics, indicating that host discrimination could be mediated by olfactory cues.

During the course of investigations into the use of the insecticides DDT and Gammexane, it has become increasingly clear that there is considerable loss through absorption into the treated surface. This loss of contact-available insecticide is most marked when simple oil solutions are used. Dosages of 100 to 200 mgms. per sq. ft., which on a non-absorbent surface (e.g. glass) are 100 per cent, toxic to flies exposed for very short periods, show little toxicity when applied to absorbent surfaces (e.g. mud).

Two new species of Cicadulina, C. ghaurii sp. n. and C. hartmansi sp. n., are described. Both occur over a wide area in Nigeria and Cameroon, and C. ghaurii has been shown to transmit maize streak virus.

The distribution of 29 species and three varieties of Anopheles in the Sudan is shown on maps. Notes are given on each one with particular reference to distribution. Reasons are given for regarding A. rupicolus Lewis as a synonym or local form of A. rhodesiensis Theo. The former spread of A. gambiae Giles into the Palaearctic Region in Egypt is discussed, and notes are given on its distribution in the Wadi Halfa area.

The general distribution of the Sudan Anophelines is discussed.

Notes are given on malaria and on Wuchereria bancrofti.

Spodoptera exempta (Wlk.) is predominantly a migrant species, but in southern Africa it is known that it can breed through several successive generations in one area. Similar observations were made for the first time in East Africa. Studies on populations in the Lambwe Valley in western Kenya revealed that during two years when the populations were monitored and one year when information was available from local farmers there were three generations each year during the period corresponding with the long rainy season. It is suggested that the Lambwe Valley presents a suitable habitat for the species to sustain its population and probably forms a breeding area for moths that might undergo large-scale migration.

The mosquitos of the reservoir area have been studied mainly with the object of planning suitable methods of controlling malaria. This paper is an account of the work done so far.

The diversity of conditions in the area, which is of such length that it has been divided into three sections, is described with special reference to the river and reservoir levels, predacious fishes, breeding places of mosquitos and water plants among which mosquitos breed.

The mosquito fauna of the area is described and observations on the breeding places and adult habits of the principal species are recorded. The large proportion of “ripe” females among Anophelines dissected is noted.

The probable effects of the reservoir conditions on the mosquitos are discussed.

Notes are given on certain species, and the relation of A. rufipes and A. pharoensis to malaria are discussed from circumstantial evidence. The former is provisionally regarded as a vector.

Control measures are described with particular reference to A. funestus (in the south), A. gambiae and A. rufipes, the latter being a vector of malaria expensive to control in the larval stage. The value of insecticidal dusts in the area is discussed.

Monitoring of Glossina austeni Newstead populations in the forested areas of Unguja island of Zanzibar has since November 1990 routinely been carried out with the sticky panel trap because commonly used tsetse traps (Biconical, Epsilon, F3) have proved to be unsuccessful in catching G. austeni. Initial studies on the catching ability of various types of sticky panels for G. austeni indicated that the monopanel was as efficient in catching flies as the 3-dimensional version and the smaller legpanel. No significant differences in catch rate and sex ratio were observed with monopanels in various colours and colour combinations. Legpanels coloured white on one panel side and blue on the other side caught significantly more flies compared with other colour combinations, but female flies were under-sampled (32%). The type of sticky material applied on the panel influenced significantly the catch rate and female ratio. During long-term trapping with baby blue and white monopanels, females were under-sampled (38–46%) except when polyisobutyleneLMW was used as sticky material. Analysis of the age composition of the sampled G. austeni females revealed that tenerals and nulliparous were well represented (11–24%). More than 20% of the trapped females were older flies, i.e. females with four or more ovulations, but this percentage dropped to 10% when Tanglefoot was used as sticky material.

Insecticide-impregnated blue cotton targets 70 × 110 cm weretested for the control of Glossina palpalis palpalis (Robineau-Desvoidy) and G. tachinoides Westwood in riverine fringing forests in central Nigeria, under wet-season conditions. Following exposure to treated cloth for 1·5 min, delta-methrin caused 100% mortality of G. p. palpalis for six weeks at 0·05% and for 13 weeks at 0·1%. Dieldrin at 5% was not very effective. At 4%, endosulfan initially caused a high mortality, but rapidly lost its activity, especially against females. By chemical analysis, 43% of deltamethrin applied to the fabric was found to have been lost within 12 weeks, in which 230 mm of rainfall was recorded. Placed 150 m apart in a fringing forest, targets impregnated with 0·05% deltamethrin caused a rapid decline in the G. p. palpalis population, and after 12 weeks only 5% of the original density was recorded. No further reduction or significant increase was observed during the following six months, though it appeared that flies caught during this period had immigrated from an adjacent undisturbed riverine forest. The effect on G. tachinoides was less dramatic, but this may have been due to the low initial density of this species, and to its greater mobility, giving rise to reinvasion from elsewhere.

Four methods have been tested of dividing cultures consisting of wheat grains containing larvae and pupae of Sitophilus granarius (L.) into samples weighing just under 10 g. and suitable for use in fumigation experiments. Two mechanical methods, each dividing a culture into two equal parts, the division being successively repeated to yield 32 samples, were shown to be satisfactory in every trial. One apparatus divided the culture on the chess-board principle, the other by means of radial fins equally spaced round the circumference of a conical divider. The standard method used at the Pest Infestation Laboratory also proved satisfactory; it consists of scooping up samples by hand radially, at random, from a culture dispersed symmetrically by pouring it over the bottom of a spherical flask, but it was evident that personal bias could be introduced by its use. The fourth method, consisting of ‘ random scooping ’, is widely used but yielded samples having considerable heterogeneity from all cultures containing larvae older than the late third instar and having a density exceeding one insect in 30 grains of wheat. This method was the only one that divided standard cultures into samples showing heterogeneity in their age structure. When cultures with an age range of only four days were divided, all four methods yielded samples for which the emergence curves were heterogeneous, apparently as a result of heating induced in samples as small as 9 g. as a result of the metabolism of the larger larvae.

The following notes on Tabanidae describe specimens collected and life-histories investigated during a recent visit to Southern Nyasaland on behalf of the Imperial Bureau of Entomology.

Cereal stands in central Europe are commonly infested with three species of aphids that may become serious pests. With increasing abundance, the proportion of a particular species in the total aphid population may remain constant, suggesting a density-independent exponential growth, or the proportion can change, suggesting density-dependent constraints on growth. The constraints that affect particular species, and thus their relative abundance, were studied. The proportionality between maximum abundances of the cereal aphids was studied using a 10-year census of the numbers of aphids infesting 268 winter wheat plots. For two species their abundance on leaves and ears was compared. With increasing aphid density the maximum abundance of Rhopalosiphum padi (Linnaeus) remained proportional, but not that of Sitobion avenae (Fabricius), which was constrained by the smaller surface area of ears compared to leaves. There was no evidence of inter-specific competition. Maximum abundance of R. padi and Metopolophium dirhodum (Walker) on leaves did not change proportionally as the proportion of M. dirhodum decreased with increasing overall aphid density. This decrease was probably caused by the restricted distribution of M. dirhodum, which is confined to leaves, where space is limiting. No change in proportion between populations was detected when the average densities were below 0.54 aphids per leaf or ear. Non-proportional relationships between aphid populations appeared to be due to spatial constraints, acting upon the more abundant population. Detecting the limitation of population growth can help with the assessment of when density-independent exponential growth is limited by density-dependent factors. This information may help in the development of models of cereal aphid population dynamics.

In the confusion existing as to the meaning of the various Entedonine genera, I think it best to define the sense in which Pleurotropis is employed in the following pages. The essential character of the genus is, I take it, the presence on the smooth propodaeum of two central keels, which diverge apically to meet the raised posterior edge of the segment. There are also present two lateral keels, as a rule strongly developed, running (inside the oval raised spiracle) along the edge from which the descent to the pleura begins. The lateral keels join the posterior edge above a generally slightly protruding angle inside the insertion of the metacoxae. The general shape of the propodaeum is transversely quadrate, not truncately triangular as in Entedon. The petiole, which joins the propodaeum by a distinct, though often very short, process, is pitted, quadrate or even sub-pentagonal in section. The proportion of the first abdominal tergal surface to the whole visible surface varies sexually and specifically from less than one-third to three-quarters.

Literature, mainly Indian, pertaining to the recorded hosts of Bracon hebetor Say and B. brevicornis Wesm., and on the taxonomy of the two species, has been reviewed. Observations on different morphological characters, including the male and female genitalia, which have been used in establishing the identity of the two species, have been made. A large number of B. hebetor specimens reared in Bangalore on Corcyra cephalonica (Stnt.), Ephestia cautella (Wlk.), Adisura atkinsoni Moore and those collected in food-grain godowns, and of B. brevicornis reared on C. cephalonica and E. cautella in Bangalore, on Nephantis serinopa Meyr. from Coimbatore (South India), on Pyrausta nubilalis (Hb.) from Canada and on cotton bollworms (?) from Delhi (North India), have been examined.

Differences in colour, relative proportions of antennal joints and punctation on the abdomen have been found to be variable and as such are not to be depended upon for distinguishing the two species. The number of antennal joints which has hitherto been considered to be the decisive character by which the two species may be separated is also not reliable as there is a wide range of variation even in the progeny of a single pair of parents. Above all, the fact that the two species interbreed and give rise to fertile offspring, which also show a fairly wide range of variation in the number of antennal joints, proves that the two are identical, and there is no ground to treat them as two distinct species, at least so far as the Indian specimens are concerned, for which Bracon hebetor Say is the valid name.

The Kerala isolate of Oryctes baculovirus (OBV-KI) was introduced into the Andaman Islands in May 1987 for the population suppression of Oryctes rhinoceros (Linnaeus). The virus was released initially at four locations along the island chain. In all the places of virus release, damage to coconut palms was reduced by about 90% within 43 months of release. At one place of virus release, Sipighat, the adult beetle population in the field was reduced by 80% within 18 months and by 96% by the end of 55th month of release. Sixty per cent of the adult beetle population in the field showed symptoms of infection 30 months after virus release. The decline in the numbers of breeding sites at Viper Island and Sipighat were 100% and 98% respectively at the end of 43 months of virus release. The rate of spread of the virus in the field was estimated to be about 1 km/month. The beetle population remained at low levels after the establishment of the virus in these islands.

Studies were carried out in Nigeria on oviposition and the deadhearts caused by Diopsis macrophthalma Dalm. on ten rice varieties. The varieties were divided into three groups according to the numbers of eggs recorded on them. Strong positive correlations existed between (a) the numbers of eggs and tillers, (b) the numbers of eggs and deadhearts, and (c) the numbers of deadhearts and tillers. Some varieties compensated for damage by the production of new tillers. In the variety Suakoko 8, most of the eggs were confined to the leaf blades in young plants and to the leaf sheaths as the plants grew older. Peak oviposition occurred 30–40 days after transplanting. Some implications of the results for a pest management programme are discussed.

Life table studies of sunn pest were carried out in Varamin, Iran, from 1998–2001 in order to determine stage-specific mortalities and the impact of specific natural enemies on population dynamics. Populations were sampled 2–3 times weekly in agricultural fields during the growing season and monthly during the period of dormancy at resting sites in nearby mountains some 30 km away from cereal fields. Adults spend a period of 9–10 months in diapause and suffered overcompensatory, density-dependent mortality during this period. Variation in adult overwintering survival was inferred to be largely a function of the physiological condition of bugs that is reduced in a density-dependent manner by intraspecific competition for food among newly molted adults prior to migration to resting sites. Adult mortality emerged as the primary factor in key factor analysis, contributing 73% of the total variance in mortality. Other important factors were egg parasitism by Trissolcus vassilievi Mayr and adult parasitism by several species of Tachinidae. Although T. vassilievi made only a minor contribution to overall variance in total mortality, it had a significant effect on the number of newly molted adults, the life stage that is most damaging to cereal crops. The equilibrium level of the pest population in wheat fields was inferred to be ca. 72.6 adults m−2, a number that substantially exceeds the economic threshold that ranges from 3–5 adults m−2.