The ovipositional responses of the stem-borer, Chilo partellus, to the susceptible maize genotype, inbred A, are higher than to the resistant genotype, ICZ1-CM. These responses are elicited by certain characters of the plants that are perceivable prior to the moths' arrival on the plants (distance-perceivable) as well as those perceivable after arrival on the plant (contact-perceivable). Distance-perceivable characters were not found to be responsible for the differences in the oviposition on the two genotypes tested.

The contact-perceivable characters of the two genotypes differ markedly in eliciting oviposition by moths. Contact with the resistant ICZ1-CM elicits much less oviposition than with the other genotype.

Insect-free tubers of four potato varieties, namely Kenya Baraka, Anett, Kerrs Pink and Roslin Gucha were exposed to adult Phlhorimaea operculella for 14 days in uncontrolled conditions in storages. On examination of the tubers 16 days after exposure, the percentage of infested tubers was determined: Kenya Baraka—62.50, Anett—77.50, Kerrs Pink—85.00 and Roslin Gucha—86.25%. The larvae made the following mean tunnel lengths: 44.65, 95.33, 88.33 and 104.23 cm in Kenya Baraka, Anett, Kerrs Pink and Roslin Gucha varieties, respectively. Although there were no statistically significant differences in the number of tubers infested (per cent), there were significant differences in the mean length of tunnels made by the larvae in Kenya Baraka and the other three varieties at P < 0.05. The mean number of larvae which survived in 10 tubers were 6.75, 11.25, 15.75 and 18.00 for Kenya Baraka, Anett, Kerrs Pink and Roslin Gucha varieties, respectively. There were statistically significant differences between Kenya Baraka and Kerrs Pink; Kenya Baraka and Roslin Gucha; and Roslin Gucha and Anett varieties (P < 0.05). Thus Roslin Gucha was the least resistant of the four varieties tested, whereas Kenya Baraka emerged as the most resistant variety. The mechanism of resistance in this case was most probably antibiosis.

A survey of Heliothis spp. and their larval parasitoids was conducted in the states of Andhra Pradesh and Maharashtra, India during the period 1977–1983. H. armigera and H. peltigera were recorded on safflower. H. peltigera was found dominant on sole crop, while both the species were equally important on intercrop. In general, eight parasitoids: four Hymenoptera and four Diptera emerged from the larvae of Heliothis spp. Six parasitoids were recorded from H. armigera larvae on sole crop and eight on intercrop safflower. The level of parasitism in H. armigera was higher on sole crop.

In a survey carried out in 1979–1982 in Sudan, 5830 tick immature stages were collected from cattle, sheep and camels and identified. Hyalomma anatolicum anatolicum, Rhipicephalus evertsi and Amblyomma lepidum immatures were feeding on cattle and sheep. Amblyomma variegatum immatures were collected from cattle. H. impeltatum nymphs were found, for the first time, to feed on camels and sheep, while H. dromedarii nymphs were recorded from camels.

Feeding H. a. anatolicum larvae on rabbits, 53.4% of the ticks behaved as three-host feeding cycle.

Competition between Corcyra cephalonica (Stainton) and Ephestia cautella (Walker) was studied in broken cocoa beans using the two species alone, introduced one before the other and together. Both species of moths cannot co-exist for an extended period and in competition E. cautella becomes extinct. The results offer an explanation of recent evidence that C. cephalonica is rapidly becoming the most important pest of stored cocoa beans in Ghana today.

The persistence of 34 formulations in the green (G) and red (R) berries of C. arabica var. typica, infested with female adult H. hampei were assayed by a dip-technique. The 3-day LC50 values in G and R (figures in parentheses) berries for thiodan EC 35 were 0.00284 (0.00327), and the relative ratio of values for other formulations were: perfekthion 1.2 (2.1) > carbicron 1.6 (2.3) > basudin 3.5 (3.2) > actellic 4.0 (3.6) > decis 4.1 (3.7) > thiodan EC 3 4.2 (4.2) > bidrin 5.8 (5.0) > malathion 5.8 (5.1) > lindane 5.8 (5.6) > ciodrin 5.9 (5.6) > folimat 6.0 (6.0) > belmark 6.2 (6.3) > aldicarb 8.0 (9.7) > nexion 11.0 (12.0)>kelthane 13.5 (15.4) > tiovel 14.6 (16.3) > dursban 15.6 (22.0) > chlordane 17.8 (23.8) > methomyl 21.5 (24.3) > aldrin 25.1 (24.9) > supona 27.2 (26.5) > dimilin 29.0 (27.5) > methoxychlor 31.7 (92.2) > chlorfenvinphos 35.8 (92.5) > dieldrin 41.2 (93.8) > phosdrin 65.0 (94.7)>sevin 104.2 (118.0)> nexagan 106.4 (121.9) > bimarit 196.4 (301.7) > azodrin 271.2 (410.4) > fenitrothion 448.3 (417.0) > chlorpyrifos 448.8 (614.3) > gardona 514.6 (703.1), -fold more than the thiodan EC 35 values.

The 7-day LC50 values for 29 formulations were ca 10–82% less than those of the 3-day values; the decrease in the values for leading formulations being thiodan EC 35 13.4 (8.3), perfekthion 6.5 (39.9), carbicron 12.4 (10.6), thiodan EC 324.3 (16.4), malathion 35.2 (25.7), lindane 82.1 (76.9) and tiovel 59.6 (67). The values for the 17 least toxic formulations (except dimilin and bimarit) showed ca 27–88% decrease during the last 4 days of observations.

Studies on damage by larvae of Eldana saccharina Walker, Chilo zacconius Bleszynski and Sesamia spp. to sugar-cane stands revealed a high degree of correlation between internode damage and stalk damage as well as between internode damage and sugar content of the canes. For every 1% increase in stalk damage there was a corresponding increase of 0.214% in the internode damage. The distribution of larvae inside the internodes was found to depend on the level of infestation. At low field infestation level (below 25 larvae per 100 canes) the distribution was random. As the level of infestation increases, the distribution becomes more aggregated. The distribution of damage in the sugar-cane field was found to depend on the overall stalk damage. The distribution tends to be more contagious when field level of stalk damage was less than 45%. The damage became evenly distributed when stalk damage rose above 60%. An estimation of average loss of sugar caused by stem-borers to the variety NCO 376 (at the field damage rate of 8.6, 10.6 and 3.1% damage for bottom, middle and top parts respectively of the cane) was U.S.S332.10 per ha of field.

Factors regulating activity of adult Rhipicephalus appendiculatus ticks were investigated. Observations were made on ticks treated to 100% hydration, 85% hydration and 65% hydration during the hot dry, hot wet (rainy) and cool dry seasons. Two-months old and 6-months old ticks of each sex were released in two different habitats in 25 × 25 cm enclosures.

Comparisons were made between the number of ticks in each group seen on the upper part of the vegetation at intervals of 2 hr during daylight hours only. Although temperature changes seemed to be the cue to tick activity, the immediate activity shown by the 100% hydrated ticks and the delayed activity of the dehydrated groups after release, suggested that only fully hydrated ticks were responsive to temperature changes.

The most commonly recorded temperatures were within the range at which tick activity appeared to be at its maximum. During the daily temperature cycle, reduced activity was observed when the temperature was outside these limits. Activity increased again as soon as the temperature returned to the optimum range.

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.

The distribution of Rhipicephalus appendiculatus on Setaria sphacelata flowerheads was investigated. Adult tick counts in a paddock, heavily infested with ticks for experimental purposes, revealed an aggregated distribution by deviating significantly from the expected Poisson distribution, but producing a good fit to the expected negative binomial distribution. A higher proportion of the ticks were on old dry flowerheads than on young green ones. Tests carried out in the laboratory confirmed the marked preference for old flowerheads and the aggregated pattern of distribution. The tick counts in the field revealed no sexual aggregation, though the total number of females collected was significantly higher than that of the males.

Groups of Rhipicephalus appendiculatus adults were prepared at three levels of hydration (100, 85 and 65%) and placed in small field enclosures. Some of the ticks were broadcast over the vegetation, while others were confined in nylon gauze bags and placed at soil level. Weight changes in the bagged ticks were monitored for 3 consecutive days by twice-daily weighing. Observations were made in the hot dry season, rainy season and the cool dry season. During the hot dry season there was a progressive loss in weight over the observation period, as during the night the ticks could not fully replace the water lost by day. In the rainy season there was an initial rapid uptake of water at night by the dehydrated groups and any weight losses during the day were easily replaced at night. In the cool dry season water losses were slight, and though ticks regained water at night, neither of the dehydrated groups became 100% hydrated during the period of observation.

Electrophysiological tests were done on larval and adult stages of Chilo partellus. The first tarsomere on the forelegs of the moths has three pairs of sensilla; two of them have similar ultrastructural details and they are innervated by gustatory cells which respond equally well to maize leaf exudate but differ in their sensitivity to sucrose. Although the third pair has morphological features resembling those of contact chemoreceptor, it responds to mechanical stimulation only. Taste sensilla on the ovipositor are more sensitive to NaCl than sucrose and they respond to the unknown components in the maize leaf exudate. On the larval maxillae the lateral styloconica sensilla are very sensitive to sucrose and the aqueous extracts from susceptible and resistant maize cultivars; the medial styloconica sensilla are mainly sensitive to NaCl and the aqueous exudate from maize stems. Preliminary tests showed that treated maize piths can provide a suitable medium for the bioassay of larval feeding behaviour.

Glossina pallidipes was sampled using biconical traps with stationary and revolving attachments in the form of blue and white flat screens. A modified biconical trap with attachment of four black strips captured the highest number of both female and male G. pallidipes Austen. However, all the stationary traps under-sampled teneral and young tsetse in post-teneral category. Biconical trap attached to a revolving component making 20 rev/min gave the best representative sample with regard to age category of females. Screens making faster revolutions resulted in larger proportions of males and hardly any old females. Flies that visited the trap with revolving screens were non-hungry, and probably mate-seeking. Those in stationary traps were mostly hungry and probably seeking blood meal.

Insect pests are major yield reducers in sorghum under traditional farming practices in Africa. The use of resistant varieties in an integrated pest management scheme provides the most cost effective and practical means of sorghum insect control. Corneous grain sorghums are more weevil resistant than their softer endosperm counterparts. A wide range of sources of resistance to shootfiy, stem-borer and greenbug are known. Breeding for resistance to sorghum insects has been practised with varying degrees of success. Greenbug resistance breeding in sorghum has been successful in the U.S.A. Stem-borers are perhaps the most serious group of sorghum insects in Eastern Africa and further efforts are needed in breeding for resistance to these pests. In an effective pest resistance breeding work, the breeder and the entomologist must work as a team to make the fastest possible progress. Where several pests are of concern in an area, genotypes with multiple resistance in good agronomic backgrounds are needed.

The efficacy of natural embelin isolated from berries of Embelia ribes Burm. against Tribolium castaneum Herbst is discussed. Embelin mixed with wheat samples at concentrations of 0.1875% and above exhibited high efficacy by bringing about adult mortality even after 8 months of storage. Productivity (progeny/adult-day) of the test insect was also reduced significantly in treatments as compared to controls at different intervals of storage. After 8 months of storage, significant reduction in F1, progeny at the lowest concentration was mainly due to larvicidal action of embelin. In the present study, embelin did not exhibit any chemosterilant action or contact toxicity to adult beetles. Germination of wheat treated with embelin even at the highest concentration of 0.750% was not impaired to any significant extent.

A new character discovered on the superior claspers of male Glossina lonipalpis Wied. is described. This is a ciliated fold in the inner angle of the distal part of the claspers. It is absent in G. pallidipes Aust. The authors believe that this character will facilitate the study of the systematics of these species; and they propose to modify the key for the identification of Glossina.

The relative toxicity of seven fumigants to the four life cycle stages of Callosobruchus chinensis (L) was determined in the laboratory. Their relative toxicities to all stages of the insect were, phosphine > methyl iodide > acrylonitrile > methyl bromide > ethylene dibromide > methyl formate > ethyl formate.