Three aromatic juvenoids were evaluated for morphogenetic activity on Schistocerca americana. Fenoxycarb, the most active insect growth regulator examined, was found to induce a significant mortality in developing fifth stage nymphs and caused severe morphogenetic damage during ecdysis to the adult. Juvenoid treatments were also observed to increase the duration of the last nymphal stage and to induce chromotropic colour changes similar to that observed in the solitary phase of the desert locust, Schistocerca gregaria Forskal.

A volatile female sex pheromone, secreted by the pygidial glands of Blattlla germaniea, which attracts males from a distance was studied. Ultrastructural studies showed common epidermal and canal cells associated with glandular cells, classified as class 3 secretory unit The thickness of pygidial glands from young virgin females Increased progressively and became larger, 10 to 13 days after adult emergence. It decreased markedly after mating and increased again after the release of the ootheca. Based on the morphology of the glands, it was further observed that B. germaniea young virgin females' attractiveness increased gradually, such attractiveness decreased at mating. After larval emergence, females' attractiveness wasonce more enhanced. Dkhktromethane extracts of pygidial glands attracted males from a distance. These results demonstrate the pheromone gradual secretion and similarly pygidial glands evolution during adult emergence.

Herbivory by insects and mites on physic nut (Jatropha curcas L.) seedlings was investigated and compared with irrigation in the semi-arid Sahelian Niger, utilizing a randomized complete block design experiment. Three water treatment protocols were applied and the types of damage were recorded. Less than 5% of the seedlings died during the 10-month trial period with sap suckers causing the most damage on the surviving plants. Plants with high production of biomass and leaf cover (foliage) were most strongly positively correlated with irrigation and were also the plants that endured the highest degree of herbivory. The low dieback may indicate that defence mechanisms counteract seedling herbivory and that drought-stressed plants invest more in their defence mechanism system than vital plants.

Soil samples collected from six localities in Pakistan—Peshawar, Quetta, Loralai, Sibi, Lahore and Sheikhupura—were screened for insecticidal Bacillus spp. Bacillus coagulane, B. megaterium and B. alvei, which constituted 50%, 33% and 17% of the Bacillus isolates respectively, were isolated and their toxicity was evaluated against larvae of the house fly, Musca domestica (Diptera: Muscidae). The most toxic bacterial isolate of the three was B. alvei (98.7% mortality) and the least toxic was B. megaterium (89.3% mortality). Extracts of experimental larvae showed the presence of strains of the respective species of Bacillus in all cases, indicating that the observed mortality in the house flies was caused by the Bacillus species.

Studies on relative susceptibility of 78 citrus varieties/hybrids to the incidence of black citrus aphid, T. aurantii under tropical humid conditions in south India revealed that none of the varieties was completely free from aphid incidence. The varieties Nagpur Mandarin and Ikeda Unshiu among mandarins; Longsport Valencia, Campbell Valencia and Washington Navel among sweet oranges; and Carrizo Citrange a hybrid and Dessert Orange, Eureka Lemon, Grape Fruit Pink and Jatti Khatti, among acid citrus group, recorded significantly least mean number of aphids per flush and can be effectively used in breeding programmes.

Antixenosis component of resistance to corn planthopper, Peregrinus maidis (Ashm.) was investigated in 10 selected sorghum genotypes at three plant growth stages (30,45 and 60 DAG) under laboratory and field (rainy and postrainy seasons) conditions. In a free-choice test, the orientationa) and settling responses of nymphs and brachypterous adults on all genotypes although influenced by the olfactory and visual responses, then- feeding was notsustained due to gustatory stimuli indicating their significant role in determining the degreeof antlxenosis. The genotypes IS 18676, IS 19349 and IS 18677 showed a high degree of antixenosls in settling fewer nymphs and adults consistently at 30,45 and 60 DAG. This finding was supported with low colonization of nymphs, and brachypterous and macropterous adults under field conditions. In addition, high degree of antixenosis for oviposition in both laboratory and field tests was evidenced on IS 18676 and IS 19349 at 30,45 and 60 DAG, but on SPV 472 and SPV 475 only at specific plant growth stages. The variability in the rate of adult colonization together with suitability of plant growth stages for oviposition has contributed to variable degrees of antixenosis for oviposition.

Ten sorghum genotypes at three plant growth stages were evaluated for antibiosis component of resistance to Peregrinus maidis expressed in terms of survival, duration and population build-up of nymphs as well as longevity and fecundity of adults. Support of nymphal survival and continued succession in mortality was evidenced on IS 18676, IS 18677 and IS 19349, indicating the influence of antibiosis factor(s) which again was supported by their prolonged duration. The growth index was consistently low at three plant growth stages on IS 18676 and IS 19349, but the genotype, IS 18677 did not express consistency on 45 days old plants. Greater longevity of adult females over males was consistent at different growth stages. Low fecundity was predominantly noticed on IS 18676, while reduced longevity was pronounced on IS 18677 and IS 19349 which was reflected in low population build-up at 15 and 30 days after infestation, when infested with 25 or 50 neonate nymphs. All these parameters contributed together suggest that antibiosis levels in IS 18676, IS 18677 and IS 19349 proportionately increased with plant age and the variability at different growth stages may be attributed to the differences in host genotypes and greatly aid as potential donors in resistance breeding programmes.

Intraspecific competition in the rice weevil, Sitophilus oryzae (L.) and the angoumois grain moth, Sitotroga cerealella (Oliv.) in grain sorghum was studied in laboratory experiments. Progeny production per female of each of the two species when reared separately, decreased as the initial parent population density increased. The number of progeny produced by Sitophilus oryzae increased to a peak, and then declined sharply with a further increase in initial parent population density, characteristic of a scramble competition. In contrast, the progeny produced by Sitotroga cerealella increased with an increase in parental density to reach a fairly constant maximum (flat topped curve), characteristic of a contest competition. It is concluded that intraspecific competition will not limit the potential of the grain moth S. cerealella of becoming a major pest of stored sorghum.

Insecticidal δ-endotoxins of Bacillus thuringiensis, Cry IA (a, b and c) were prepared from over-expressing cells of Escherichia coli and bioassayed against the third instars (6-day-old) of the spotted bollworm, Earias vittella Fabricius (Lepidoptera: Noctuidae), using artificial diet. The median lethal concentration (LC50) values were calculated for 6 days of exposure to δ-endotoxins. Cry IA(a) was found to be the most toxic (LC50 141.2 ng/cm2) followed by Cry IA(a) and Cry IA(b) with LC50 values of 224.5 and 300.5 ng/cm2 respectively. A highly significant reduction in larval weight took place in the surviving larvae treated with sub-lethal doses of the insecticidal crystal proteins.

Permethrin, deltamethrin, fenvalerate and cypermethrin were evaluated for their termiticidal efficacy in a graveyard test. Semul wood, Salmalia malabaricum veneers (size 15.00 × 6.00 × 0.06 cm) were impregnated with concentrations of 0.25, 0.50 and 0.75% aqueous solution of these chemicals. Fenvalerate provided 100% protection for 44 months at all three concentrations. Cypermethrin provided 100% protection at 0.50 and 0.75% concentrations, while permethrin and deltamethrin provided 100% protection at 0.75% concentration for 7 and 10 months, respectively.

The insect growth regulator, 6′,7′-epoxy-3′-ethyl-7′-methyl-dec-2′-enyl 6-ethyl-3-pyridyl ether, at 10 ppm applied to rearing media, did not prevent oviposition or hatchability of the eggs of Tribolium confusum. The insect growth regulator (IGR) apparently had no effects on the development of younger larvae, and no morphological abnormalities were observed in these instars. However, the IGR prevented metamorphosis of the last larval instar. These larvae continued to moult several times, became larger than larvae in untreated food, but failed to pupate; as a result, no adults emerged from the treatments.

It has become increasingly noticeable that common features of many forest and forest/ savanna foci of West African human trypanosomiasis (WAT) are peri-domestic tsetse populations closely associated with domestic pigs. Recent evidence from various sources almost completely proves that, in at least some WAT foci, domestic pigs play an active role as reservoirs of Trypanosoma brucei gambiense. On the basis of this assumption, various aspects of Glossina palpalis and G. tachinoides local distribution and ecology, in relation to domestic pig and human populations, are discussed.

In those WAT foci where domestic pigs are kept, tsetse are widely distributed in forest islands, forest/plantations, and riverine forests, but major concentrations are in villages containing pigs. Close pig/fly relationships at the village level, involving peri-domestic feeding, breeding and resting behaviour on the part of flies, could be important factors in maintaining T.b. gambiense transmission in pig populations.

Endemic transmission of WAT to man could occur, either in villages where low pig densities dictate that a significant proportion of the fly population must also feed on man, or away from the village as a result of contact with infected flies which have strayed from a village transmission cycle.

The development of epidemic conditions could be explained, on the basis of changes in pig density and resultant changes in fly feeding behaviour. The sudden reduction of a pig population could result in an increased number of infected flies feeding on man, until such time as the fly population became stabilized on a reduced pig population (or on other hosts if pigs disappeared totally). During the period of increased feeding of flies on man, T.b. gambiense transmission could be intense.

Minor flare-up of WAT could occur if small numbers of infected pigs were introduced into a village area which had no previous history of pig husbandry. If a loose man/fly association persisted in such a village, endemic WAT could become a characteristic feature of that village.

Because of the fluidity of pig distribution and density, infected pigs could be instrumental in dispersing T.b. gambiense from village to village within a WAT focus and contribute to the persistent character of the focus. Pig movements involving much greater distances could also be important to the transfer of T.b. gambiense strains from one focus to another.

Correlations were established between an endemic infestation of the coffee margorodid, Icerya pattersoni Newst and the characteristics of the veins of the leaves it infested in four coffee species in Kenya. The attack was variable between species although there was an affinity for it to be confined to midribs of definite length and thickness and laminal veins of quantifiable dimensions.

This short communication describes the morphological features of three specimens of Hyalomma truncatum which dropped off artificially infested rabbits in the laboratory.

The ability of males of Ephestia cautella to mate and transfer sperms aftergamma radiation as 5–6–day old pupae was investigated. The results indicate that gamma radiation had no significant effect on mating, sperm transfer and percentage of egg hatch.

Malathion tolerance of the rose-grain aphid Metopolophium dirhodum (Walker) reared on the ancient wheat variety Emmer (Triticum dicoccum L.) was tested by topical bioassay and found to be lower than that of aphids reared on the modern more susceptible variety Marts Kinsman (T. aestivum L.). On both varieties, tolerance was greater at stem elongation than at the tillering stage of plant growth. All statistically significant differences when plants were treated with Cycocel and MCPA showed that the two chemicals, respectively, reduced and increased aphid tolerance to malathion, in keeping with the effects of the chemicals on induced plant resistance to aphids reported in the literature. Probit mortality slopes were not progressively altered by changes in LC50, so that similar differences in aphid tolerance to malathion were found at both LC59 and LC90 levels.

A bioassay was developed to assess the in vitro feeding responses of Chilo partellus larvae to susceptible (Inbred A) and resistant (MP 704) maize varieties. Consumption of internode tissues from the two maize varieties differed while the reverse was true for the nodes. Aqueous extracts from the two varieties caused a decrease in feeding and weight gain, but these effects were more evident in MP 704 than in Inbred A treatments. This suggests that MP 704 has a water extractable factor affecting weight gain negatively. Dose-response curves of neural responses from the maxillary styloconica sensilla showed that aqueous extracts from the two maize varieties evoked different functional forms of impulse frequencies especially in the lateral sensilla. These observations suggest that the quality of gustatory stimuli in the two maize varieties differs.

Life history components, especially those of the adult stage, were investigated in Aedes aegypti and Culex quinquefasciatus in the laboratory. Males of Cx. quinquefasciatus had a greater expectation of life at adult eclosion than males of Ae. aegypti. There was no statistically significant difference in the means of life expectancy for females of Ae. aegypti versus those of Cx. quinquefasciatus. In both species, males had a shorter life than females. The two species exhibited considerable heterogeneity for reproductive characters. Females reproducing for the first time were younger in Cx. quinquefasciatus than in Ae. aegypti. Net reproductive rate and the per capita rate of increase were greater in the former than in the latter species. Cx. quinquefasciatus had a shorter generation time than Ae. aegypti. The data reported here are inconsistent to varying degrees when compared with data gathered by other workers from the same species. The results are discussed with reference to the theoretical constructs of the life history theory.

Observations of the diurnal resting behaviour of Glossina longipalpis and Glossina fusca congolensis were carried out at Ele forest, Oke-Ako between September 1975 and May 1976 both inclusive. The two species of tsetse were observed resting most frequently on underside of stems and branches with diameter range 1–60 mm. Some G. fusca congolensis rested vertically. Whether resting vertically or obliquely, this species always rested with head pointing downwards. More than 95% of G. longipalpis and G. fusca congolensis rested between the heights of 20–240 cm. Preferred resting objects included shrubs, young saplings, climbers and, during high temperatures, bases of tree trunks.

For control purposes it is suggested from the above information that a discriminative and selective spraying of the area be planned for the late dry season and early rains when fly populations are more concentrated and individual flies tend to rest at lower heights. The spraying which should be directed to the undersurface of resting objects will help to reduce the risk of trypanosomiasis at the Oke-Ako cattle ranch.