The African armyworm, the larva of the night flying moth Spodoptera exempta (Walk.), feeds on young stages of cereal crops, sugar-cane and all types of grasses in some 30 countries of Africa, from Mauritania and Senegal in the north-west to Ethiopia and Somalia in the north-east, and southwards to Namibia and South Africa. Between 1960 and 1982, outbreaks of armyworms were recorded regularly in East Africa during the ‘outbreak season’ between November/December and June/July, often from southern Tanzania towards the north or north-west at monthly intervals. Analysis of occurrence of outbreaks in Tanzania, Kenya and Uganda in the 1971/72–1973/74 seasons, and rainfall records in Tanzania for 1969–1975, showed that the occurrence of armyworms in Tanzania coincided with the onset and northward progression of the rains up to Kenya and Uganda. Additional results from monthly maps, tables, graphs and histograms of armyworm occurrences in administrative units (Districts and Provinces) in Tanzania, Kenya and Uganda for 20 years (1960–1979), showed that the onset, progress and duration of armyworm attacks in all districts and provinces in each country, tend to follow certain geographical patterns which can be monitored through the use of insect traps and Agricultural Extension Services. In this way, coordinated surveillance of priority areas could enable farmers, pastoralists, Plant Protection and Pest Control Units of the Ministries of Agriculture to identify likely areas and periods of armyworm attacks, so that they could organize strategic or emergency control of armyworms with insecticides when the larvae are still young.

Marked individuals of Zonocerus variegatus were released in batches of 100 per developmental cohort at definitive loci in either an open field of mainly giant star grass, Cynodon sp. or a cultivated farm of cassava, Manihot esculenta. The distance and direction of movement of individuals in any given stadium were determined in metres and angular degrees. The mean distances moved by marked Z. variegatus for each day of observation were determined by Clark's root mean square formula.

The results showed that older cohorts covered more distance during a given period than young cohorts. However, while the first instar nymphs moved significantly less than any other cohort, the differences in the mean daily distances moved by nymphs of the second through the sixth developmental instars in the cassava farm were not statistically significant. For all cohorts, Z. variegatus covered significantly more distances in the open field than in the cultivated farm, suggesting that the availability of food inhibited the rate of dispersal of Z. variegatus. There was no significant difference in the number of Z. variegatus found on the different aspects of the compass.

Trypanosomiasis outbreaks of great severity, both medical and veterinary, still occur. At the present time some of these outbreaks can be contained by implementation of plans based on sound knowledge of tsetse distribution. However, for many countries such knowledge is fragmentary. For this reason the second edition of tsetse distribution maps is to be regarded as provisional only, pending the availability of more accurate data. Some of the new information that has been received since 1973 is reported. It is concluded that a programme of intensive revision is needed before it can be claimed that tsetse situation in Africa is well understood.

The very tiny eggs of Daraba laisalis are often laid hidden between the body of egg fruits and its persistent sepals. After 4–5 days nearly all eggs hatch. The first instar caterpillar enters an egg fruit within 30 min of hatching, spends 8–15 days within it at a temperature of 24–32°C and r.h. 73–96%; it comes out a much bigger caterpillar to pupate in any convenient but hidden place near the egg fruit. The development of larva and pupa to adult and the morphology of the first and last instar larvae, the pupa and the adult are described. Behavioural peculiarities, longevity and predators of larvae are also mentioned.

In many tropical countries, increasing use is being made of irrigation to grow more food for the world's expanding population, but as well as bringing benefits irrigation also causes problems. The proliferation of standing water provides numerous habitats for snail intermediate hosts of schistosomiasis and mosquito vectors of diseases such as malaria and filariasis. Thus, while irrigation schemes can be successful in providing more food they may be accompanied by increases in vector-borne diseases. In some schemes resettlement of people creates overcrowding and slum conditions which can result in a deterioration in general health and hygiene, facilitating the spread of water related diseases such as cholera, typhoid and various dysenteries. Efficient vector control, supported by the people, is needed to reduce the undesirable effects of irrigation.

Studies of the epidemiology of visceral leishmaniasis in the West Pokot focus have revealed that Sergentomyia bedfordi, S. antennatus and S. schwetzi are the most abundant sandfly species. The latter have been shown to feed mainly on lizards. Phlebotomus martini was encountered in termite hills in the ventilation shafts, and showed an even distribution among the termite hills throughout the district where kala-azar cases were detected. Investigations into the relationship between termite hills and the presence of kala-azar cases in various homes were carried out. All homes afflicted with kala-azar had a termite hill or hills within a 10-m radius. The period of time spent in own homestead by each kala-azar case was to establish if each kala-azar patient contracted the disease in the focus of investigation.

A year round ecological study of Glossina morsitans submorsitans variety ugandensis was carried out from September 1980 to August 1981 in the Finchaa river valley in the western part of Ethiopia. Two sampling methods, namely vehicle patrol and screen/handnet capture were employed. The latter was more efficient. The effect of various environmental factors (e.g. altitude, climate, vegetation etc.) that determine the eco-distribution of this species of tsetse were analysed. The most significant finding was that tsetse were distributed far above the previously known altitude limits.

Bendiocarb 80WP, applied at 1 and 2 g/m2, was compared with BHC 30WP, applied at 0.5 g/m2 of gamma isomer, for the control of the important Chagas' disease vector Triatoma infestans, in Brazil. The insecticides performance was evaluated in groups of about 20 heavily infested, mud- or adobe-walled houses selected on the basis of pre-spray sample data. These houses, together with a check group of untreated, infested houses, were sampled for the presence of T. infestans pre-spray and at 1, 3, 5, 7 and 9 months post-treatment employing a systematic search technique with the aid of a flushing-out agent. This method was found to detect infestations in from 71 to 95% of the samples taken in groups of infested, untreated houses. Treatment with bendiocarb 80WP at 2 g/m2 resulted in the elimination of T. infestans from 40 to 50% of the infested houses, whereas BHC 30WP at 0.5 g/m2 reduced the number of infested houses by 70–80%. In the houses where the bugs were not eliminated the populations were markedly reduced in size by the insecticides, but became reestablished by 5 months post-spraying. Detailed analysis of the field trial sample data together with the results of a simple laboratory experiment suggest that although bendiocarb WP powder may be intrinsically more toxic to triatomines than BHC WP, it is less persistent when applied in house largely constructed of mud.

Aleurolobus barodensis (Maskell) was more abundant than Neomaskellia andropogonis Corbett on sugar-cane in Pakistan. Azotus delhiensis Lal, Eretmocerus sp., Prospaltella flava Shafee, Amitus sp. and Tetrastichus sp. parasitized nymphs and pupae of A. barodensis and E. serius Silvestri those of N. andropogonis. Chrysopa carnea Steph., Brumoides suturalis (F.), Catana parcesetosa (Sic.), Oenopia sauzeti Muls., Scymnus sp. and S. nubilus Muls. preyed on the immatures of the aleurodids.

In Peshawar valley where the crop is aerially sprayed twice a year to control Chilo infuscatellus Sn., Tryporyza nivella F., A. barodensis and Pyrilla spp., the rate of parasitism on A. barodensis was very low and its density was very high, being 330 immatures/leaf at Charsadda and 425 at Mardan in November 1979. At Sialkot (Punjab) where the crop is not sprayed, the rate of parasitism, mainly by A. delhiensis and Amitus sp., at this time was 22% and the density of A. barodensis was 70.4 immatures/leaf. The maximum rate of parasitism was 71% in January. The abundance of A. barodensis in Peshawar valley seems to be due to the mortality of natural enemies because of aerial spraying, therefore, judicious use of insecticides and redistribution of natural enemies in these areas is recommended.

The effect of five juvenile hormone analogues (JHAs) on the embryonic development of Panstrongylus megistus, a vector of Chagas' disease, was studied. Four compounds, N-(2,5-dichlorophenyl)-3, 7-dimethyl-2™6-octadienylamine, N-(5-chloro-2-methylphenyl)-3, 7-dimethyl-2, 6-octadienylamine, 3,7-dimethyl-6, 7-epoxy-l-(3,4-methylenedioxyphenoxy)-2-nonene, and 6, 7-epoxy-3-ethyl-7-methyl-l-(3, 4-methylenedioxyphenoxy)-2-nonene, which are potent JHAs for P. megistus, were effective in blocking eclosion when applied at 0.5μg/egg to eggs during the first half of embryonic development. If these compounds were applied after the start of blastokinesis, then they were no longer active as ovicides. The possibility is raised that JHAs may be useful as control agents in complementation with insecticides which do not possess ovicidal activity.

An analysis of the variation of fore-, mid- and hindgut contents in third- to sixth-instar nymphs of the African grasshopper, Zonocerus variegatus, freshly caught every hour in the field, and also left without food for 1, 6 and 12 hr, showed that gut motility and the movement of ingesta through the gut was maximal at 08.00–10.00, 13.00–14.00 and 16.00 hr. Movement of ingesta was very slow at night. A diurnal rhythm therefore governs gut emptying. Nymphs, confined in jars with leaf discs, fed from 07.00 to 19.00 hr over the temperature range 17–34°C. Most food was eaten after 13.00 hr when it is warmer. Field insects feed during the night as well. Midgut α- and β-glucosidase activity was detected at all times of testing (06.00, 12.00, 19.00 and 24.00 hr), but the levels of activity were lowest at 12.00 and 19.00 hr.

Cowpea is one of the most widely grown leguminous crops in Africa: in Kenya it occupies over 66,000 ha and Coast Province ranks second to Eastern Province with about 5200 ha. It is an important food item consumed both as a vegetable and as a grain. Unfortunately, it suffers from both preharvest and postharvest infestations which accounts for serious losses of the crop. With the introduction to Kenya of improved varieties from IITA, Nigeria, such losses would be increased due to varying susceptibility in different pest ecosystems. The objective of this study therefore was to observe the infestation of the IITA varieties and compare them with local cowpea varieties collected from different parts of Kenya. The work was conducted at C.A.R.S., Mtwapa from 1979 to 1981 inclusive. From the study, five different bruchid species were identified as infesting cowpea varieties in the field. These were Collosobruchus rhodensienus; C. phaseoli; C. chinensis; Bruchidius atrolineatus; and C. analis; in order of decreasing abundance. Over 50% of the bruchids found in the field were C. rhodensienus while Zabrotes spp. and C. maculatus (F) were never encountered in the field. Although the IITA materials were introduced because of their yield potential, it was found that some of them were as susceptible to preharvest bruchid attack as the locally available materials. The short rains season had more bruchid infestations than the long rain season. There were also fewer eggs on pods of local varieties and fewer bruchids emerging from seeds of local as compared to IITA varieties. The results however were not significantly different. Further work should be done to establish the complex of bruchids found in stored cowpea varieties, the losses caused and control measures applicable to reduce damage.

Population regulation is briefly explained, and the demographic parameter, r, is identified as a symptom of the dynamic balance between density-independent and density-dependent factors that respectively disturb or regulate population equilibria. Evidence for density-dependence in tsetse populations is reviewed under the general headings of direct and indirect observations. Direct evidence comes from predation experiments on both adults and puparia, and from experiments that measure the feeding success of tsetse on bait animals. Indirect evidence arises from detailed analyses of fly-round records. Natural density-dependence in tsetse populations, when it occurs, is shown to be considerable, and must always be allowed for in control programmes whose effectiveness it at least partly determines.

In the Zambezi Valley of Zimbabwe, ULV applications of non-residual insecticide (endo-sulphan and NRDC 161) were made to a 1.8 × 1.8 km block of woodland infested with Glossina morsitans morsitans Westw. and G. pallidipes Austen. The recapture rates of marked flies released in the centre of the block, and recaptured in odour-baited traps in and around the block, indicated that the insecticides killed about 97% of flies that had been released 1–4 hr before spraying. Catches of unmarked male G. m. morsitans in the centre of the block declined after the insecticide applications, but there was no clear effect on catches of female G. m. morsitans and both sexes of G. pallidipes. Data for the movement of marked flies suggested that the minimum daily rates of movement were about 700 m for male G. m. morsitans and about 800 m for the other tsetse. An increase in dawn temperatures, from 17.5 to 27.5°C, was associated with an increase in the rate movement of G. pallidipes in the early morning. The failure to detect changes in the unmarked populations of female G. m. morsitans and both sexes of G. pallidipes was attributed to the high mobilities of these flies and demonstrated that unmarked populations could not be studied satisfactorily in small plots; studies based on marked populations are recommended for such plots.

The effects of population density on nymphal development and mortality, synchronism in moulting, body weight and reproductive development of ensuing adults were studied in Dieuches femoralis Eyles. The development time of larvae was found to vary with density such that the development time decreased as the number of larvae per cage increased through 5, 10, 15 and 30. The most crowded cages also produced the heaviest adults and females from these cages developed the greatest number of eggs. The solitary larvae produced more females than males.