Behavioural-antennal responses of tsetse to buffalo urine, which has been identified as a potent olfactory attractant, were investigated. Tsetse Glossina morsitans morsitans rapidly raised their antennae upon stimulation with the odour of buffalo urine. Flies showed a clear preference for the undiluted urine, though antennal responses even to 100,000 × diluted urine were significantly different from control, indicating the high efficacy of the attracting compounds present in it. Fresh buffalo urine was the most attracting as compared to 4- and 8-day-old urine. The dichloromethane extract of fresh urine was as active as the natural product, indicating that the attracting compounds were extractable into dichloromethane. Under laboratory conditions, responses of males to the urine were significantly more than females.

In the following report no attempt has been made to render uniform the style of the reports of the four speakers. For brief summaries of the subjects which were to be discussed by the absent members of the panel, the reader is referred to the abstracts published by them in the ‘Programme and Abstracts of the Congress’.

Five barley varieties, viz. Proctor, Kenya Research, Tumaini, MPYT 169-2Y and Can B35/2, were tested in the field to evaluate their resistance traits to D. flavibasis. Can B35/2 was identified as a moderately resistant variety useful for reference in further work. The varieties were observed to recover their growth after the infestation. Visual growth recovery scores in the field experiments suggested the tolerance type of resistance.

Prococenes I or II (20–100 μg/insect) were topically applied to third instar nymphs of the grasshepper, Heteracris littoralis. Both compounds led to different degrees of precocious metamorphosis, irreversible with time, at the subsequent moults. Precocene-treated third instar nymphs gave rise to precocious adults at the following moult, though some of the nymphs responded and metamorphosed precociously in the fifth instar. Ovarian development was inhibited by precocene II. Meanwhile, juvenile hormone (20/μg/insect) restored normal ovarian development to some extent.

Tanzanian strains of Tribolium castaneum (Herbst), Gnatocerus maxillosus (F.), Sitophilus oryzae (L.) and Sitophilus zeamais Motschulsky were confined to maize grain treated with a dilute dust of permethrin at the rates of 1.5, 3.0 and 6.0 ppm active ingredient. The adult mortality and resulting F1 generation were recorded. G. maxillosus was very susceptible to the insecticide and even the lowest dose brought complete control. T. castaneum adults survived all treatments but few F1 were produced. Adult survival of s. oryzae and S. zeamais was progressively reduced by increasing dosage, although S. zeamais was much less susceptible to the treatment than S. oryzae.

The repellency of grain, treated with 3.0 ppm permethrin, to S. oryzae, S. zeamais and T. castaneum was tested in a simple choice chamber. Neither male nor female T. castaneum were repelled but significantly fewer eggs were laid on treated grain. For both Sitophilus spp there was no significant difference between the numbers of females or eggs observed on treated or untreated grain, but males were repelled from permethrin.

The importance of these results is discussed in relation to a recent recommendation that the treatment of shelled grain with 3.0 ppm permethrin should be adopted in Tanzania in order to control Prostephanus truncatus (Horn), a new and serious storage pest.

The paper reviews advances in our understanding of the vectorial capacity and vector–parasite relationship in Kenyan sandflies since the early 1900s (when sandflies were first reported in Kenya). Of the 38 species of sandflies known to occur in Kenya to date, three (Phlebotomus pedifer, P. martini and P. duboscqi) can naturally carry biochemically and serologically confirmed Leishmania (aethiopica, donovani and major, respectively) and 12 (Phlebotomus rhodhaini, Sergentomyia garnhami, S. squamipleuris, S. africanus, S. kirki, S. ingrami, S. antennatus, S. bedfordi, S. schwetzi, S. affinis, S. graingeri and S. clydei) carry various flagellates of biochemically or serologically unknown character.

Current research on naturally infected wild-caught sandflies indicates that L. aethiopica promastigotes have close association with structures resembling a peritrophic membrane and invade P. pedifer gut cells. Promastigotes invade the malpighian tubules of S. garnhami and S. antennatus.

Studies on laboratory-reared sandflies show that P. martini is susceptible to L. donovani amastigotes and that cultured promastigotes of L. donovani can survive in the guts of S. schwetzi, S. ingrami and S. adleri.

Experimental infection of sandflies with Leishmania is discussed and priorities for laboratory work set.

A forest ecosystem was divided into four zones: the original primary rain forest, secondary forest of short trees and bushes, tertiary Lantana thickets, and fallow plots. Tsetse, Glossina pallidipes Austen, were trapped in the four zones, dissected and the incidence of infection by the non-occluded virus determined. Tsetse density was relatively higher in the fallow land, and lowest in the primary forest. Virus infection was highest in the tsetse trapped in the primary forest (7%), and decreased progressively towards the fallow plots (1.8%). There were more young tsetse (less than 40-days-old) in the primary and secondary forests, whereas the Lantana thicket and fallow land had older flies (more than 40-days-old). Possible explanations of these observations are discussed.

The presence of microfilaments (MF) and microtubules (MT) in the cytoskeletal systems of unicellular eukaryotes, the differentiations of their fine structure and topography within the cells, as well as the tremendous variety of motile phenomena manifested by Protista, made it impossible to treat the subject systematically and thoroughly during one session. The Symposium concentrated therefore on a few selected topics: the organization of the MF cytoskeleton of free living amoebae, its role in producing endoplasmic flow, cell-to-substratum attachment and ectoplasmic movements, as components of the amoeboid mode of locomotion; the transition from the MF to the MT system in the case of amoeba-flagellate transformation; molecular mechanism of operation of the most specialized MT system, in cilia and flagella; and calmodulin as a likely universal sensor allowing Ca2+ to control the motility. All these subjects were covered by seven lectures.

The development of Dysdercus voelkeri on three dwarf and short-season varieties of sorghum: BES, HP3 and HP8 and its damage to the grains were studied in the laboratory and greenhouse, respectively. An average development period of 27 days was recorded on the three varieties. The fecundity, fertility, live-weight and dorsal surface area were significantly higher in insects that developed on HP8 than in those that developed on BES and HP3. There were, however, no significant differences in these parameters except fertility between the insects that developed on BES and HP3.

The highest grain damage of 56.6% was recorded for HP8, while 51 and 27.6% grain damage were recorded for BES and HP3, respectively. The potential pest status of D. voelkeri on these new and improved sorghum varieties in the southern Guinea and derived savanna zones of Nigeria is confirmed in these studies. Effective control of this bug and other sucking insects at the milky stage of grains' development is suggested for high yield and good quality grains.

Cohort tests in screened cages confirmed that the cowpea varieties TVu 2994, TVu 3709, EW/1, BPL-3–1, ER-7 and Vita 5 have promising levels of resistance to Cydia ptychora (Meyrick). The resistance was found to be mainly explained by antixenosis with respect to oviposition.

In no-choice tests in the laboratory, high larval mortality was recorded in TVu 3709 and BPL-3–1. Additionally, comparatively lighter-weight final instar larvae and adult females with reduced fecundity, fertility and longevity were reared from TVu 3709 and TVu 2994. Larvae reared on Vita 5 were slower in developing to adults than on other varieties; they were also relatively lighter in weight, while adults emerging from them showed reduction in size and fecundity. It is therefore concluded that resistance in TVu 3709, TVu 2994, BPL-3–1 and Vita 5 is partly due to larval antibiosis.

Chlordimeform (CDM), tested by topical application, was found to be toxic to both male and female tsetse with the maximum effect some 72 hr after treatment. Median lethal doses were approx. 0.4 μg/fly for unfed adult tsetse of both sexes, 100% mortality at 72 hr was achieved with 2 μg/fly. Mature fed females were less susceptible to chlordimeform, the median lethal dose for 72 hr being 12.5 μg/fly. High doses of chlordimeform depressed the weight of puparia from survivors, but had no effect upon fecundity. Sublethal doses caused a significant depression of feeding activity, but did not cause hyperactivity or disrupt fat body lipid reserves.

Identification and taxonomy of the genus Leishmania is considered in brief, drawing on existing review articles. A fully-referenced synopsis of clinical, epidemiological, biological, immunological and biochemical criteria and methods used for typing leishmanial parasites is given and discussed. Classical and modern approaches are compared. Leishmanial phylogeny, the value of numerical taxonomy and the possibility of sexual recombination in leishmanial organisms are also considered.

Laboratory studies were conducted to assess the infestation potential of Callosobruchus maculalus (Fab.) on 12 elite and one local cowpea cultivars which were stored under subtropical conditions. Index of susceptibility, loss in grain quality and the number of adult progeny that emerged from previously infested grain were the criteria used to assess the vulnerability of the cowpeas to post-harvest infestation. Cultivars TV × 309–1C and TV × 1193–10F showed some degree of resistance to post-harvest infestation by C. maculalus and could therefore be stored safely for a relatively long time. TV × 1192–01D and TV × 1999-1D were the most susceptible cultivars to post-harvest attack by C. maculatus. Length of storage adversely affected the ability of the cultivars to resist the insect attack. Crop resistance, adequately supplemented with good sanitation, can be profitably applied to control insect infestations in grains during storage.

Besides distinguishing between ‘zooplankton’ and ‘phytoplankton’, one of the more useful ways for oceanographers to classify planktonic organisms is by size (e.g. Sieburth et al., 1978). Of the free-living protozoa in the marine plankton, most fall into the ‘microplankton’ (20–200 μm, including many of the sarcodinans and ciliates as well as a number of larval metazoa and the larger phytoplankton) and ‘nanoplankton’ (2–20 μm, including the smaller ciliates and most of the heterotrophic flagellates as well as most of the phytoplankton).

Five types of haemocytes were identified in Poecilocerus pictus (Fab.) and their ultrastructural details and differential counts were studied. The types identified are the prohaemocyte, plasmatocyte, granular haemocyte, oenocytoid and coagulocyte. In response to the injection of yeast cells into the haemocoel, changes in haemocyte morphology and differential counts occurred. The predominant cell involved in phagocytosis is the plasmatocyte, followed by granular haemocyte.

Zea mays L. and Rottboellia exaltata L. were the main graminaceous plant species infested by Eldana saccharina Walker, the major pest of sugar-cane in southern Ghana. Other stem-borers of sugar-cane, Sesamia botanephaga Tams and Bowden, Sesamia penniseti Tams and Bowden, Sesamia calamistis Hampson and Chilo zacconius Bleszynski, were recorded on Zea mays, Echinocloa pyramidalis (Lamk.) et Chase, Rottboellia exaltata, Panicum maximum Jacquin and Oryza sativa L.

All the stem-borer populations except E. saccharina on Rottboellia exaltata increased on their host plants. Sesamia and Chilo species were present from January to December on Echinocloa pyramidalis. It is concluded that these alternative host plants provide a potential source of stem-borer infestation on sugar-cane at Asutsuare in southern Ghana.

Observation on natural enemies of the stem-borer complex on sugar-cane in southern Ghana indicated that Descampsina sesamiae Mensil (Diptera:Tachinidae) is the most important larval parasite of Sesamia species. The relative abundance of this tachinid parasite appeared to vary with the rainfall pattern throughout the year and with the phenology of the sugar-cane plant. The rate of parasitism was found to be higher in the outgrowers fields than in the sugar estate's fields. Differences in cultural practices used as well as the type of vegetation bordering the sugar-cane fields, were believed to be responsible for the difference in the rate of parasitism of D. sesamiae on Sesamia species.

The systematics of phlebotomine sandflies have significantly advanced in the last two decades through the incorporation of a growing body of information on the biology of sandflies and the introduction of new techniques: chromosome analysis, enzyme electrophoresis, detailed morphological studies, laboratory rearing and colonization, and multivariate morphometrics. These techniques have been used mainly in the study of intra-specific variation of vector species. The rôle of sandfty systematics in the epidemiology of leishmaniasis is discussed.

Field and laboratory observations of Epicerura pulverulenta Hampson (Lepidoptera: Notodontidae) elucidated the role of biotic factors in the moth's populations. Natural enemies recorded included. Gryon and Telenomus spp (Hymenoptera: Scelionidae) which parasitized 33% of eggs studied. Also, about 4% of the larvae were parasitized by the dipterous tachinids Zygobothria atropivora Robineau-Desvoidy, Exorista xanthaspis Wiedeman, Blepharella sp., and P. quadrizonula (Thompson); and the perilampid Perilampus dubius (Walker), all solitary endoparasitoids. The predators included Belanogaster dubius Kohl. (Vespidae), Glypsus erubescens Dist. (Pentatomidae), Camponotus maculatus F. (Formicidae) and a kite (bird). They accounted for 12% of larval mortality. In addition, 27% of the 4346 larvae studied developed mycosis caused by Paecilomyces farinosus (Dickson ex Fries) Browne and Smith. A nematode, Hexamermis sp. was also associated with the larvae killing 1.5% of them. High pupal mortality was observed, but the cause was unknown.

The ability of the African trypanosomes to vary their surface coats of glycoprotein antigens during infections of susceptible host animals has prevented the development of vaccines employing cell surface proteins, as is being attempted with other parasitic protozoa (see Cohen, 1986). Since the phenomenon of antigenic variation in protozoa was the subject of another symposium, of the five papers presented in this symposium one dealt with the possibility of sexual phenomena occurring in trypanosomes, one with the transmission of the organisms by tsetse to vertebrate hosts and one with the characteristics of the trypanosomes isolated from man. The fourth paper described the vertebrate host response to the parasites and the fifth described the control of such infections by chemotherapy.