Incorporated in this paper were the results of a study made on the quantitative variation of total carbohydrate, protein and lipid in whole body, fat body and integument of the larval and pupal developmental stages in rice moth, Corcyra cephalonica (St.) a storage grain pest. All three macromolecules referred to in case of whole body, exhibited a progressively decreasing trend from larva to pupa. In fat body total carbohydrate and protein contents were more in pupa than larva, while in integument the said nutrients were less in pupa than larva, showing the reverse results. The lowering down of the nutrients' level under stress caused by pyrethrum (a botanical insecticide) was also observed. The physiological and statistical significance of these findings was discussed.

The study reported here evaluated the distribution, relative abundance, and malaria transmission potential of Anopheles mosquitoes at 30 sites representing different ecological strata in western Kenya. Seasonal variation in anopheline densities and transmission potential, as expressed by Entomological inoculation rates (EIR), was investigated. Of the 6491 indoor resting anopheline mosquitoes collected at the 30 sites, 91.3 % (n = 5926) were An. gambiae s.l. and 8.7 % (n = 565) were An. funestus with an average house density of 6.58 and 0.63, respectively. Analysis of the data indicated significant variation in mosquito densities between study sites, species and season. High densities of both An. gambiae and An. funestus were recorded in the northern and northeastern parts of the district, while generally low densities were recorded in the south. Anopheles gambiae s.s. and An. arabiensis comprised 60.3 % (n = 3573) and 39.7 % (n = 2352) of the total number of An. gambiae s.l. mosquitoes collected, respectively. The composition of the An. gambiae s.l. sibling species showed temporal and spatial variation. Entomologic inoculation rates were estimated at 1.55 and 0.12 infective bites per person per month for An. gambiae s.l. and An. funestus, respectively. This study reveals considerable seasonal and site-specific variation in vector distribution, composition and transmission potential. Application of control interventions must therefore consider seasonal variations since the vectorial system changes quite rapidly over a short period of time.

The hormetic influence on silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) of the juvenile hormone mimic ω-formyl longifolene oxime propargyl ether (NL13) was assayed. Emulsions containing 2.5, 5.0 and 10.0 ppm of the compound were administered topically as a single dose, to two popular commercial silkworm hybrids, viz. KA × NB4D2 and PM × NB4D2, at 24,48, 72 and 96 h into the 5th instar, and economic characters of the larvae and resultant cocoons measured. A medium and absolute control were maintained in parallel. It was found that administration of 5 ppm of NL13 to 48-h-old 5th instars resulted in the maximum improvement in commercial traits. The possible role of exogenous JH-like compounds in eliciting this response in silkworm is discussed.

The termite Macrotermes herus builds domed earth mounds with no external openings. The internal structure is described here. There is no specialized ventilation system in the mound, unlike those of other Macrotermes species.

As an important measure for increasing grain production, hybrid sorghum has been cultivated in the whole area of the Peoples Republic of China since 1970. Over the past 10 years the sorghum shootfly has gradually become the worst pest of sorghum in several places in the southern parts of China. In 1973, some regions of Gung Dong, Gui Chou and Gung Xi Provinces were affected by the shootfly with a rate of 30% for the heavier damage, and a few even exceeding 90%.

Thirty-five pearl millet cultivars of short, medium and long maturity cycle were screened in Senegal during 1985–1986 crop seasons to study field reaction to the attack of stalk borer, Coniesta (Acigona) ignefusalis Hmps.; spike worm, Heliocheilus (Raghuva) albipunctella De Joannis; millet midge, Geromyia penniseti Felt; head smut, Tolysporium penicillariae Bref; and ergot, Claviceps fusiformis Lov. Insect and disease incidence varied considerably depending upon cultivar maturity cycle. Least susceptible cultivars were IBV-8001 and P8 against spike worm; Zalla, NKK, P8 and M2D2 against head smut, and Ex-Darou against ergot. Cultivation of IBV-8001 has been suggested in northern and central Senegal. However, studies on identification and utilization of resistance sources of wide genetic diversity and multilocational tests may be necessary.

Twenty-seven species of Chilo which infest graminaceous crops are listed. The effects of various cultural practices such as time of planting, plant density, field sanitation, tillage, mulching, intercropping, proper fertilizer and water management on field populations of Chilo spp. are discussed. These practices have great potential as components of IPM for resource-limited farmers in the tropics.

Thirty-five grain sorghum genotypes representing 6 variable groups (A/B-lines, R-lines, commercial varieties, germplasms, mutants and locals) were evaluated for the orientation, colonisation and oviposition responses of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), governing the antixenosis component of resistance. In free-choice tests, the orientation and colonisation responses of the weevil were identical among all the genotypes at 24 h, varied at 48 h, and differed widely by 72 h after adult release. High degrees of antixenosis for colonisation by the adult weevils were observed among all the genotypes except 2077A and 2219B, which suggests a predominant reaction to gustatory rather than visual or olfactory stimuli. One to five egg plugs per seed were oviposited, frequently near the endosperm close to the seed base. Greater levels of antixenosis for oviposition were noticed in 2077B, DJ 6514 and IS 11758 in free-choice tests, and 2219B, M 148–138, P 721 and Nizamabad (M) in no-choice tests. To the contrary, M 35–1, Swati and Lakadi showed greater susceptibility for oviposition. Significantly less damage to seed was observed on 2219A/B, 116B, IS 9487, IS 11758, CSV 8R(M) and Local Yellow. Although the differences in seed weight loss were not significant, this parameter was relatively lower in AKMS 14B and 2219B than in the other genotypes. This indicates the need to increase the levels of resistance among the parental A/B-lines in the development of hybrids, in order to ensure better protection from rice weevil infestation in stored sorghum.

Studies were conducted to determine the effect of temperature and diet on the development of Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) (Lepidoptera: Crambidae). Developmental times of C. partellus and C. orichalcociliellus for the egg, larval and egg-adult life stages were inversely related to temperature. The larval developmental period of C. orichalcociliellus reared on artificial diet was longer than the developmental period on natural diet. Chilo partellus had a higher intrinsic rate of natural increase than C. orichalcociliellus at all diet/temperature combinations except natural diet at 31°C.

Epidinocarsis lopezi an exotic parasitoid to Africa, was first released to control the cassava mealybug (CM), Phenacoccus manihoti, at IITA (Ibadan) in November 1981, and a year later at Abeokuta, both in southwestern Nigeria. Population dynamics study of CM and its natural enemies was conducted for 4 years. CM population peaks usually occurred during the second half of the dry season (January–April). E. lopezi was the only natural enemy that was found during the whole year and in high densities. Parasitization rates of E. lopezi alternated with CM densities, thus suggesting a regulatory effect on CM populations by this parasitoid. CM populations were drastically reduced in release fields when compared with control fields. Subsequently CM populations have been maintained below injury levels for 4 years. E. lopezi is considered an efficient parasitoid of the CM.

Efficacy of olfactory attractants incorporated in biconical traps to enhance the catch size of Glossina pallidipes Austen was investigated. Preliminary studies considered the effectiveness of a mixture of waste products from buffalo (Syncerus caffer) and that of warthog (Phacochoerus aethiopicus). The results were compared with the known tsetse olfactory attractants, carbon dioxide and acetone. When the waste product components from buffalo were used in the traps separately, buffalo urine was found to be by far the most effective. This component, used in its natural state inside the trap, increased G. pallidipes catches almost 10-fold when compared with the control catch.

At intervals of 2 months over 1 year, 64 royal cells were removed from mounds of Macrotermes michaelseni to find out whether a new royal pair was produced. In five mounds replacement reproductives were found. Young reproductives from incipient laboratory colonies were never accepted as replacements if they were introduced after the removal of the primary reproductives. One out of 10 royal pairs was accepted if the royal cell was introduced immediately after removal of the original one, and three out of 10 survived if the royal cell was introduced 1 week after the removal of the original one.

Replacement reproductives were only produced when nymphs or alates were in the nest at the time the primary reproductives were removed. It was not possible to find out at what time after the removal a new royal pair was accepted but measurements of the replacement queens showed that they can become fully physogastric within 7 months.

In leaf disc choice assays and topical application experiments, the neem (Azadirachta indica) limonoids azadirachtin, salannin, deacetylgedunin, gedunin, 17-hydroxyazadiradione and deacetylnimbin were found to be potent antifeedants and growth inhibitors to the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Azadirachtin was most potent in both respects. Gross dietary utilisation (efficiency of conversion of ingested food) of H. armigera was also decreased following topical application as well as after treatment in the diet. Growth inhibition in topically treated H. armigera may be primarily attributed to decreased food intake. The antifeedant and growth-inhibitory effects of the neem limonoids are discussed.

Some morphological characters of the rice plant were found to be associated with resistance to the African striped borer, Chilo zacconius Bleszynski. A very low, but negative correlation was recorded between percentages of bored stems and plant height. Positive correlations were recorded between percentages of bored stems and stem diameters, stem thickness, length and width of flag leaves and number of tillers per plant. High silica content in rice plants appeared to be a strong factor in resistance to the striped borer. Negative correlations were recorded between percentages of crude silica content of the plants and percentages of bored stems and number of living larvae per plant. Although each of these factors appeared to contribute to borer resistance, none by itself could be said to be the main cause of such resistance, as some varieties did not conform to some of the characters.

Insect pests are major constraints in cowpea production. Breeding for insect resistance is a major objective of cowpea improvement programme at IITA. Resistance to leafhoppers and aphids has been incorporated in advanced breeding lines thus eliminating the need for other control measures. Similarly, a moderate level of resistance to thrips and cowpea storage weevil has also been incorporated thus reducing the damage due to these two pests. A moderate level of resistance to legume pod-borer and pod sucking bugs has also been identified and is being incorporated in advanced breeding lines. The long term strategy is to develop cowpea cultivars with multiple resistance to insect and diseases with superior agronomic characters and local adaptability.

Males of the Triatominae, Panstrongylus megistus and Triatoma infestons, show a considerable difference concerning the time necessary for them to acquire the capacity for the first mating. P. megistus copulates from the eighth day of adult life, irrespective of whether or not it has been fed, while T. infestons copulates about 17 days after the imaginai moult and only after a blood-meal. These differences might be due to the secretory activity of T. infestons male accessory glands whose full development is reached only after two saturant blood-meals. If allatectomy is performed in male P. megistus soon after the imaginai moult, accumulation of secretion does not occur in 3 of the 4 accessory glands. Topical application of precocene II (200 μg/insect)a few days before or soon after the imaginai moult in P. megistus, halves the amount of secretion in the accessory glands.

Preliminary investigations have shown the presence of pathogenic fungi in natural populations of the cassava green spider mites. Among others, Entomopthora sp. and Hirsutella sp. were isolated from dead mites sampled from the field. Laboratory bioassays have given mite mortality of up to 60%, indicating the possibility of utilizing some of these pathogens in mite control. Tests with Beauveria bassiana, isolated from lepidopteran pests, have also shown that the mite is susceptible to this fungus.

Rice germplasm comprising 66 lines/varieties was evaluated under field conditions for two wet seasons against a yellow stemborer, leaffolder and whitebacked planthopper (WBPH) at the vegetative and panicle initiation crop stages. Glasshouse screening of germplasm for WBPH resistance was done at the seedling stage. At the vegetative stage, over the 2 years, 18 lines/varieties showed leaffolder damage from 6.21 ± 0.33 to 9.99 ± 4.07%, while at the panicle initiation stage, six lines/varieties showed damage from 8.77 ± 1.25 to 12.25 ± 4.67%. A highly significant correlation between flag leaf width and per cent infested leaves at the vegetative (r = 0.88) and panicle initiation (r = 0.79) stages was recorded. No significant correlation was observed between plant height and leaffolder infestation at the vegetative stage; however, it was significant at the panicle initiation stage (r = 0.37). The dead heart (DH) damage at the vegetative stage over the years was less than 1% in six lines/varieties, while at the panicle initiation stage, seven lines/varieties showed whitehead (WH) damage ranging from 1.29 to 1.92%. A highly significant correlation was observed between plant height and per cent DH and WH at the vegetative (r = 0.73) and panicle initiation stages (r = 0.81). Such a relationship was not observed between leaf width and stemborer infestation at both stages. Two lines, viz. IR 59 547-235-3-3 and SPR 85 163-5-1-2-4, were resistant to the WBPH under glasshouse screening, whereas 20 lines were moderately resistant and the remaining lines were susceptible.

In this study, the effects of yeast protein hydrolysate (YPH): sucrose proportions in the adult diet of the Ethiopian fruit fly Dacus ciliatus Loew on survival, pupal production, and endogenous lipid and protein contents were investigated. Small populations of the fly were fed diets containing various proportions of YPH and sucrose under low-humidity and high-humidity conditions. The YPH: sucrose proportions ranged from 20 to 50%. We monitored the patterns of survival, pupal production, and individual endogenous protein and lipid loads (only under high-humidity conditions) in flies maintained on various adult diets. The survival patterns of both males and females under high-humidity conditions were inversely proportional to the proportion of YPH in the diet. Mortality of some adult flies was related to the stickiness of the highly hygroscopic adult food mix. By contrast, the survival patterns of males and females maintained under low-humidity conditions were directly proportional to the proportion of YPH in the diet. Apparently, there was no effect of diet type on the number of pupae produced; on the sucrose-only diet, flies produced significantly fewer pupae. Protein content in the flies increased significantly as the proportion of protein in the diet increased, but lipid content was clearly not related to food constitution. Based on these results and recent evidence from studies in other fruit fly species, we concluded that a large amount of protein is deleterious to the fruit flies. Workers in rearing facilities should investigate and tailor different food-delivery systems, e.g. separate dishes for carbohydrates and the food mix, and reduce the amount of YPH used in industrial adult diets.