The infectivity and pathogenicity of three native entomopathogenic nematodes (Heterorhabditis (HNI 0100 and sp-CIAT) and Steinernema (SNI 0198)) were evaluated in third instar larvae of Phyllophaga menetriesi (Blanchard) under laboratory conditions. Concentrations of 7000 and 13,000 infective juveniles per millilitre were applied to the coleopteran larval host (individuals) that had been placed in plastic cups with 40 g of sterile sand at 5.8% (w/w) moisture. The evaluations were done 5 and 10 days after treatment. It was observed that both the percentage of infectivity (74.5%, n = 247), measured in terms of percentage of penetration and the percentage of pathogenicity (10.5%, n = 247) of the three native nematodes were significantly different due to the treatments. Steinernema had the highest values of infectivity (>80%), but no pathogenicity. In contrast, the treatments with Heterorhabditis, despite having the lowest degree of infectivity (52.9%), had the highest mortality values (31.6%). Therefore, the Heterorhabditis strains were considered to be the most promising as biological control organisms within an integrated pest management programme due to their higher degree of pathogenicity. Nevertheless, different strains and species of native nematodes should be evaluated in all the developmental stages of the pest.

Mobility of tsetse flies is influenced by various factors including the search for a blood-meal. Field observations on the feeding behaviour of tsetse are difficult. The use of bait animals for experimental purposes may indicate food sources but not host selection under natural conditions. Availability and density of a particular potential host species in a tsetse habitat can influence the feeding habit of the latter. Flies are capable of adapting to new host species in the absence of the usual ones. Host selection might be due principally to availability of host(s) and not based on true preference. Tsetse flies respond to visual stimuli from moving objects. Their shape, colour and size are important factors eliciting visual response. Whether these factors are distinguished separately or in combinations is not clear. Odour emanating from live hosts causes up-wind olfactory response towards the source(s), resulting in actual landing on test targets even when the hosts are out of sight. The components of odour have not been isolated. It is therefore doubtful if host selection can be associated with odour, as this might imply that tsetse can differentiate the odours of the different potential hosts. The difficulties in ascertaining true host selection by tsetse are discussed to stimulate further investigations.

Simple models can be used to study the effects of factors involved in trypanosomiasis transmission, provided rough parameter estimates are available. The models should also be tested against field data; more complex models are needed whichrelate prevalence to the sensitivity of the diagnostic method, and take account of age-dependent changes in host susceptibility.

During foraging, parasitoids of insect herbivores are aided by chemical compounds generally termed ‘infochemicals’, to locate their hosts. The origin of the infochemicals varies; they may be derived from the herbivore itself or activities related to the biology of the herbivore, the host plant, or from interactions between the plant and the herbivore. This paper reviews the status of research in this area, and presents an account of the infochemicals used by African stemborer parasitoids during foraging, as well as recommending possible areas for further investigation. The information generated has potential for application in behaviour modification of parasitoids species in biological control programmes.

A method of marking tsetse flies is described based on the transfer of fluorescent pigment from marked males to females during copulation. Powder applied between the coxae of the male lodges in the scutellar groove of the female during mating. Powder persists well on males before mating and on females afterwards. Individual males can mark several females, and the marks of different males can be detected on females after multiple mating. Aspects of behaviour which may possibly be investigated using this method are described.

The geographical distribution and the biology of the different species of tsetse fly are closely connected with the vegetation. Any modification in the vegetation cover may therefore change, in one way or another, the dynamics of tsetse populations and, consequently, influence the transmission of trypanosamiasis. Irrigation and rural development programmes which often drastically change the natural vegetation of vast areas will therefore result in major changes in the incidence, epidemiology and epizootiology of trypanosomiasis.

Only very limited studies have been carried out on this important problem and it is very difficult, if not impossible, to make a review of this subject as the data available are very fragmentary and often relate to specific situations.

The main purpose of this article is not only to review the data and information available at present, but also to identify and stress our lack of knowledge and the need for further research.

The problems created by establishment of irrigation and rural development programmes, industrial scale plantations, irrigated cultivations, livestock rearing centres are highlighted without neglecting the sociological and medical aspects of population transfers connected with these development programmes.

The conclusions attempt to identify the research which should be carried out in the field and propose some recommendations drawing attention to both the health services and to those responsible for planning and establishing irrigation and rural development programmes.

In intertropical Africa, various haematophagous Diptera are considered responsible for the maintenance and spread of cases of cattle trypanosomiasis in regions where tsetse flies are absent. In comparing early observations with the results of two recent tsetse control campaigns, this paper raises the question of whether the role of machanical vectors is as important as that normally attributed to them, and stresses the insufficiency and impressive nature of available information on this important epidemiological problem, which requires much more intensive research.

Eggs and larvae of the bollworms Earias spp. followed a uniform distribution on G 27, LD 133, LD 230 (Arboreum) and F 414 (hirsutum) cotton varieties in Ludhiana (Punjab). Clump distribution of Earias eggs and larvae on the four cotton varieties may result from environmental heterogeneity. Although Earias gravid females laid maximum eggs at the top (41–50 cm) plant canopy mostly, examination of the whole length of the plants is suggested for sampling Earias on the four varieties.

Sample sizes of 10 plants in arboreum and seven in the hirsutum variety resulted in reliable estimates of population at 5% risk level. Injured fruiting bodies and larval numbers were significantly and positively correlated.

Examination of Giemsa stained smears made from the peripheral blood, liver and spleen of hand-caught lizards from West Pokot area showed the presence of seven out of the nine Plasmodium species of lizards which have been previously described in Africa. These species are redescribed using a set of biological characters and procedure which enabled a large quantity of each stage of any species to be studied, measured and compared. The utilization of these characters and procedure was a reaction to the multiple infections in individual lizards and a wide host range of each species among lizard species. The adoption of the criteria is recommended for future taxonomie work on lizard Plasmodia in Africa.

A key which brings together all the previously described species of lizard Plasmodia and the new species encountered in the present investigation is presented. The key is simplified so that it can be of use to epidemiologists and pathologists who may work on saurian malaria in Africa.

Laboratory reared populations of Spodoptera exempta (Wlk.) had higher net reproductive rate and capacity for increase on maize, Zea mais L. and star grass, Cynodon dactylon (L.) Pers. than on Kikuyu grass, Pennisetum clandestinum Chiov., Guinea grass, Panicum maximum Jacq. and Setaria plicatilis (Hochst.) Hack. These parameters were greatly influenced by the larval mortality, but in all cases they were greater than one demonstrating that S. exempta populations can multiply on all the host plants tested. Since no populations with stable age distributions are known for S. exempta the net reproductive rate is more appropriate than the capacity for increase in estimating its population growth.

This paper discusses insect behaviour and host plant resistance under single-plant species resistance and plant population resistance. Under single-plant species resistance, the effects of repellents, surface texture, shape and colour to insect behaviour are briefly reviewed and discussed. The effects of plant species diversity and plant density on insect behaviour are discussed under plant population resistance. Where possible, this discussion is illustrated with examples from recent behavioural studies on the weevil, Sitona lineatus L.

Farmers in the groundnut belts of Mali, Burkina Faso, Niger, Nigeria and Benin in West Africa were interviewed for their ability to identify economically importanct soil pests infesting their groundnut (Arachis hypogaea L.) crops, and to obtain information on farm histories and cultural practices which may influence soil pest infestation and spread in a field. Termites, whitegrubs and millipedes were recognised by the farmers as being the most important soil pests, with termites being the most damaging group. A negative correlation (P < 0.05) was found between the number of years a farm was cultivated and the frequency of termite occurrence in it. Information on cultural practices obtained from interviews and field visits indicated that practices such as late harvesting and the leaving behind of residues of previous sorghum, millet and maize crops increased termite infestation. The cutting down and burning of the vegetation in a farm before planting significantly (P < 0.05) reduced the percentage of plants attacked by termites. The cultivation of short-duration (< 100 days) varieties to escape drought at the end of the cropping season did not significantly reduce termite damage, due to late harvest. Other farmers' practices which are likely to have contributed to soil pest damage are also discussed.

Mites are known to live in a diverse number of habitats, but only recently have they been collected in large quantities from the tropical canopies, where they have a diverse feeding habit.

We studied the canopy oribatid mites from five localities of Mexican oak species. Foggings with a natural pyrethrum in aqueous solution were employed to obtain the arthropods living on the canopy of the oaks. Specimens were taken from two collections made in February and August of 1997.

The total number of mites obtained with the two foggings was 5824 specimens. Most of them (95%) were collected during the rainy season and only about 5% during the dry season. The Mesostigmata were represented by 194 specimens, Prostigmata by 849 and the Cryptostigmata (or oribatids) were by far the most abundant, with a total of 4781 specimens. This group represents only 3% of total mite abundance during the dry season and 97% during the rainy season.

Quercus crassipes harboured more oribatid mites during the dry and rainy seasons, and the most important mites in abundance and frequency were Camisia sp., Phauloppia sp. and Scapheremaeus sp.

The development, life table and intrinsic rate of natural increase of the reduviid predator Rhynocoris fuscipes (Fabricius) on Spodoptera litura Fab., Earias vittella Fab. and Corcyra cephalonica Stainton under laboratory conditions were constructed. Fecundity, longevity and minimum developmental period of the predator were dependent on the prey diet and decreased in the order: S. litura, E. vittella and C. cephalonica. The mean number of female progeny produced over the entire period (the gross reproductive rate) was 43.0, 37.5 and 32.5 on S. litura, E. vittella and C. cephalonica respectively. The net reproductive rate (Ro), intrinsic rate of increase (rc) and weekly multiplication rate were also highest on S. litura followed by E. vittella and C. cephalonica.

Studies were conducted using a water-based trap baited with the synthetic female sex pheromone to gain further understanding on the effect of trap height and spacing in relation to crop height on catches of males of the millet stemborer, Coniesta ignefusalis (Hampson) (Lepidoptera: Pyralidae). Regardless of crop height, catches were greatest at trap heights of 0.10 and 0.50 m when the traps were stacked vertically. When traps were sited singly at 50 m spacing there was no significant difference in catches at the different heights. When trap spacing was varied from 50,15, 5,1 to 0 m, male moth catches in traps increased at lower trap heights, regardless of crop height. Comparison of catches in light traps and pheromone-baited traps showed a significant positive correlation. These findings have implications for both monitoring and development of millet stemborer control systems through mating disruption and mass trapping.

Insects have evolved a potpourri of mechanisms for manipulating the allelochemicals that fortify their preferred host plants. A concatenation of physiological and biochemical events frequently follows the ingestion of a toxic natural product and can eventuate in a variety of fates for the compound. A particular allelochemical may be absorbed, metabolized, and sequestered, whereas the fates of concomitant natural products may be very different. Some compounds may be directly excreted in the faeces and their concentration will thus mirror that in the plant. In other cases, selective absorption and sequestration combine to biomagnify minor constituents so that the concentration of these sequestered compounds in insect tissues diners drastically from their concentrations in the host plants.

The acridid Romalea guttata is utilized in this paper as a paradigmatic insect which eclectically processes ingested allelochemicals from a wide range of host plants. This generalist herbivore is eminently suitable as a model because it feeds on plants containing a veritable pharmacopoeia of toxic compounds. The proven sequestrative potential of its defensive glands further qualifies R. guttata as an excellent candidate for determining the fates of toxic phytochemicals. An analysis of this insect's processing strategies for the compounds ingested after feeding on catnip (Nepeta cataria) reveals that for R. guttata variety is the spice of herbivorous life. The results of this investigation persuasively demonstrate that each insect species—and the phytochemical mixture that it ingests—must be regarded as a unique evolutionary case that constitutes a distinctively idiosyncratic phenomenon.

Results of 7 years' experiments conducted in South China indicated that root-zone application of systemic insecticides effectively controlled nearly all the potential insect pests of rice—the yellow stem-borer, the striped stem-borer, the pink borer, the rice leaf folder, the rice gall midge, the brown planthopper, the greem leafhopper, the rice thrip and the rice weevil. Altogether, 16 compounds have been evaluated for the control of various species. Applications of carbofuran mixed with derivatives of nereistoxin (padan, thiocyclam or dimehypo) in the root-zone were found to be most effective against the major insect pests. The merits and demerits of root-zone applications has been discussed in this paper.

Seasonal incidence of the sorghum earhead bug, Calocoris angustatus Lethierry, was studied by sowing the crop once in 10 days, throughout the year during 1978 and 1979, as well as by sowing it at fortnightly intervals from early “kharif” to late “rabi” during 1979. The bug was found throughout the year except for a few weeks during March, April and May. The milky stage of the earhead was the most preferred stage compared to pre-flowering, a third flowering, flowering and ripening stages. The adults dominated during pre-flowering and a third flowering stages whereas nymphs dominated during milky and ripening stages. The computed seasonal indices were higher during August (230), September (222), October (224) and January (215) which coincided with blooming and milky stage of sorghum in general fields. Correlation studies between the bug population at the milky stage and maximum temperature indicated negative and significant (r = -0.2967) relationship, and positive and significant (r = +0.2727) relationship with relative humidity. Low incidence of bugs was observed on the crop sown during June.

The population and distribution pattern of the black parlatoria scale, Parlatorio zizyphus (Lucas) have been investigated. This scale had two annual peaks of abundance in September and May. It passed through three annual generations, the first in September–October, the second in March–April and the third in June–July on grape fruit trees. The build up of insect population on different zones of grape fruit trees in different seasons of the year was studied. The insect distribution of different insect items were significantly affected at different heights and directions of the trees. The highest population tended to be accumulated on the lower and middle shady zones of the trees in different seasons. With regard to directions the central core of the tree harboured the highest population followed by the west direction and the lowest population was accumulated on the north or south direction in the fall and spring. In summer, the highest population settled on the south direction in contrast to the east or north directions, which harboured the lowest population. The mode of insect distribution is discussed in correlation with the environmental conditions.

A list of 88 nominal taxa of mosquito species (Diptera: Culicidae) originally described from Uganda is given. The list includes 68 valid species, 7 subspecies, 6 varieties, and 7 synonyms, within 10 tribes, 14 genera, and 13 subgenera. All 3 subfamilies of Culicidae (Anophelinae, Toxorhynchitinae, and Culicinae) are represented. The type localities of the different species are updated for quick identification based on the present political boundaries within Uganda. The species stages that are as yet not fully described in the literature, and those species whose breeding habitats are unknown are indicated.