The population patterns of eggs, larvae and puparia in the bean plants and leaf punctures made by adults were investigated during cropping (March–July and October–January) and noncropping (July–October) seasons at two sites in Kenya. The beans planted in noncropping seasons had more leaf punctures, eggs, larvae and puparia than beans planted in cropping seasons. Beans planted in noncropping season attracted unusually high population from surrounding weeds as well as previous crop which cause severe damage. Under field conditions Ophiomyia spencerella Greathead and Ophiomyia phaseoli Tryon were the species of bean flies infesting the bean plants in all seasons. Both O. spencerella and O. phaseoli normally oviposited in punctures on the leaves but O. spencerella also oviposited in the stems of bean seedlings.

A total of 39 strains of Anopheles stephensi, an important urban malaria vector, were collected from various parts of India and maintained in the insectary for this study. Based on the egg-float ridge number, 19 strains were classified into ecological variants and 32 strains were exposed to chlorpyrifos and propoxur to investigate their resistance status. Filter paper containing freshly laid eggs was taken, the ridge numbers on the floats were counted under the microscope, and strains were classified into ecological variants. Of the 19 strains, 18 were of ‘type form’, with ridge numbers ranging from 15 to 21. The Papareddipalya (PRP) strain belonged to the ‘intermediate form’, with 14 to 17 ridge numbers. Larval bioassays were carried out according to the procedure of the WHO. For chlorpyrifos, the lowest LC50 value was 0.00107 mg/l (Padmanabhanagar strain) and the highest value was 0.0403 mg/l (GOA-A strain). Furthermore, the lowest LC90 value was 0.00368 mg/l (Delhi strain) and the highest was 0.1746 mg/l (GOA-A strain). For propoxur, the lowest LC50 value was 0.00029 mg/l (Goraguntepalya strain) and the highest value was 0.0037 mg/l (JP Nagar strain). Moreover, the lowest LC90 value was 0.00094 mg/l (Goraguntepalya strain) and the highest value was 0.0115 mg/l (JP Nagar strain). The tolerance values ranged from 1.26 to 37.68 for chlorpyrifos and from 1.34 to 12.77 for propoxur. All the type forms were from urban and semi-urban locations, and the intermediate strain was from a semi-urban location. The bioassay results indicated that the strains of An. stephensi were more susceptible to propoxur than to chlorpyrifos.

The amount of free amino acids increases during the larval development. The accumulation is greater during the later larval life followed by an abrupt decline in the defaecating larva and early prepupa. The overall decrease in the free amino acid content during the period of metamorphosis is more in case of drones in comparison to that in workers. However, the amount present in adult drones is less than that of workers. The changes in the free amino acid content during the post-embryonic development of workers and drones of Apis cerana indica seem to show sexual dimorphism.

—A revision of the Neotropical species of the Forcipomyia squamitibia group, revealed three new species, F. (F.) catarinensis from southern Brazil, Colombia and Costa Rica, F. (F.) quechua from northwestern Argentina and F. (F.) rioplatensis from northeastern Argentina and northwestern Uruguay, which are described and illustrated. Forcipomyia (F.) squamitibia Lutz is redescribed from the original type material, a lectotype is designated, and F. (F.) soriai Wirth is recognised as a junior synonym. The remaining known species of this group are diagnosed, and keys to males and females are provided for the identification of the nine recognised species.

Surveys were conducted in farmers' fields in Zambia during the 1987/88, 1988/89 and 1989/90 cropping seasons, to evaluate the extent of attack on maize by stalk borers and their distribution in some selected maize growing areas in three agroecological regions. Infestation levels varied from season to season. Infestations were low (0.5–13%) in the Southern province: Gwembe Valley and Livingstone in region I and Choma and Kalomo in region II. Infestation levels in other areas ranged from 21–75%. Three species of stalk borers, Busseola fusca, Chilo partellus and Sesamia calamistis were recorded. Their composition and proportion in the complex differed from place to place. C. partellus occurred at an altitude range of 350–1170m, B. fusca occurred at 1032 to >1300m above sea level. B. fusca was the most widely distributed and predominant.

The juvenoids fenoxycarb and methoprene were evaluated for morphogenetic activity on last-instar nymphs of the American bird grasshopper, Schistocerca americana (Drury) (Orthoptera: Acrididae). Topical application of fenoxycarb induced supernumerary nymphs, adultoids and adults with curled wings. Methoprene yielded similar morphogenetic effects although at reduced levels of activity. Of particular interest, however, is the discovery that, in addition to its morphogenetic activity, fenoxycarb causes significant mortality in developing fourth-, fifth- and sixth-instar nymphs.

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 effect of potassium application to maize plants on the development, survival and fecundity as well as larval and pupal weight of Sesamia calamistis and Eldana saccharina were studied in the laboratory. Six different potassium treatments corresponding to 0, 30, 60, 60, 90, 120 and 150 kg K2O/ha were used. Potassium had no influence on larval and pupal developmental time or longevity of adult S. calamistis. The highest larval mortality was observed at 0 and at 150 kg K2O/ha. Increased doses (> 60 kg K2O/ha.) tended to reduce pupal survival. The lowest pupal weight was obtained at 150 kg/ha whereas fecundity was negatively related with potassium. The highest values of intrinsic rate of increase (rm) and net reproductive rate (Ro) were obtained with 60 kg K2O/ha and lowest with 150 kg K2O/ha. For E. saccharina, potassium had no significant effect on larval and pupal developmental time, larval survival, and pupal weight. The highest larval weight, pupal survival and fecundity as well as rm and Ro values were observed at 90 kg K2O/ha.

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.

Field and laboratory observations revealed that the placement of eggs of the sorghum shootfly, Atherigona soccata, among sorghum stems tended to be random or slightly aggregated rather than regular, which suggests that the site of oviposition by a female is little or not determined by the presence of other eggs already laid. The possible effects of this type of distribution on the mortality of the first-instar larvae are briefly discussed.

Larval instars of Chilo partellus Swinhoe reared on sorghum plants were determined. The larvae were separable into five non-overlapping instars by analysis of variance and Duncan's multiple range test, frequency distribution and scatter diagram of the head capsule widths. Head capsule increment from one instar to the next conformed to Dyar's rule, while at the same time agreeing with Richards' hypothesis. The stadial periods for the five instars were 6, 4, 5, 3 and 7 days, respectively.

The oviposition behaviour of spotted bollworm, Earias vittella Fab. was studied on 23 cotton genotypes under field and laboratory conditions. There were substantial differences in the number of eggs laid on different genotypes. More eggs were deposited on the bolls compared to leaves and squares. The relative oviposition preference differed under the field and laboratory conditions in the case of some genotypes. Leaf hairiness was significantly and positively correlated with number of eggs laid both under field and laboratory conditions. The effect of oviposition on varietal susceptibility appeared to be modified through other factors, such as gossypol and tannins. However, oviposition non-preference was one of the important resistance mechanisms in some cotton genotypes.

At 25°C and 70% r.h. larvae of Spodoptera exempta develop faster and pass through five instars on star grass, Cynodon dactylon (L.); Pers. maize, Zea mais L.; and Kikuyu grass, Pennisetum clandestinum Chiov. whereas on guinea grass, Panicum maximum Jacq.; and Setaria plicatilis (Hochst.) Hack, the development is not only slower, but the larvae pass through six and seven instars, respectively. Samples of larvae reared on the former grass species suffer high mortality only at the first and the last instar stages so that the distribution of per cent mortality is U-shaped. On the latter host plants, the mortality during the first instar stage is equally high and continues through the subsequent instars with no obvious peak towards the end of the larval life. The samples on C. dactylon and Z. mais had much higher growth indices than those on P. maximum and S. plicatilis. C. dactylon is a preferred natural food plant of S. exempta in the field, and these investigations demonstrate its value and importance.

Descriptions and morphometrics of the eggs and waxen structures on the nymphs and adults of Orthezia insignis are given. Architecturally, the waxen designs are similar throughout the nymphal instars but vary in the construction details. On the newly hatched (issued) nymphs only structural outlines are visible under a binocular microscope and on older instars, wax secretions become progressively more copious and conspicuous. At adult stage, the greatest amount of wax is used to construct the ovisacs. Reproduction was parthenogenetic and embryogenesis was characterized by three colour changes of the eggs: the white, newly laid eggs successively turn light yellow; bright yellow and then brown before eclosion. The frequency of nymphal issuance was influenced by the relative positions of the egg batches inside the sac. Nymphs hatching from eggs laid late in life, took longer to scramble out of the sac. Evidence deduced from the rate of nymphal issuance and the mean number of light yellow eggs at any given time, suggested that ovulation, embryogenesis and eclosion are probably synchronized biological activities in Orthezia.

Development of nymphs in the laboratory took approx. 42 days and was marked by three stadial stages. Morphometrics of the right metathoracic femurs from dead nymphs and exuviae reliably confirmed a similar developmental pattern in wild population.

Blister beetles have recently become the key pests of food crops in Mali and Senegal. The endemic areas of most destructive species, Psalydolytta fusca Oliv., P. vestita Duf., are situated in Northeast Mali and Central South Senegal. Host plants of certain species were identified. Light traps were used to study population dynamics of major species at Béma and Samé (Mali), and at Bambey, Gossas, Sokone and Nioro du rup (Senegal). Abundance of P. fusca and P. vestita populations in September–October generally coincided with sorghum and pearl millet flowering. Number of P. vestita beetles trapped was higher than that of P. fusca.

A ‘rice garden’ with monthly plantings of rice was established in an irrigated lowland area in April 1993 and continued for 3 years. Populations of the most common insects, the stalk-eyed flies, Diopsis spp., and the green leafhoppers, Nephotettix spp., and spiders and stemborer damage varied distinctly in relation to month of transplanting. Arthropod populations also exhibited distinct patterns in relation to crop growth stage. Grain yields varied with month of transplanting but there was no distinct trend from one year to the next. This study indicated that continuous cropping of the same fields over a 3-year period did not result in a build-up of insect pests or a decline in grain yield.

Studies on the population dynamics and species composition of the sorghum stemborers Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), Busseola fusca (Fuller) (Lepidoptera: Noctuidae) and Sesamia sp. were conducted at Melkassa, Rift Valley of Ethiopia, during the 1990 and 1992 cropping seasons. Chilo partellus at 92% dominated the species composition. Busseola frisca made up 7.7% and Sesamia calamistis less than 1% of the borers. Occurrence of partellus declined with delay in planting until the third planting ( early June to early July) then increased during late planting in July. Busseola fusca alone, however, tended to increase in numbers with delay in planting. In Melkassa area, early planting in July could be considered as the most suitable, with low borer numbers, damage symptoms and resulting in fewer stalks with peduncle damage. Grain yield was also higher during early planting in July while the lowest yield was obtained during late planting in July. Weather factors showed no consistency but relative humidity seemed to have a significantly negative correlation with insect numbers in the last two plantings in 1992.

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.

Field tests were carried out to compare the performance of a new tsetse trap, the Nitse (I and II) with the biconical, F3 and NGU traps respectively at the Yankari Game Reserve, Bauchi State, Nigeria. The game reserve harbours Glossina palpalis, G. tachinoides and G. morsitans submorsitans species. The biconical trap was used as the standard. The sites had been cleared of vegetation; they were 5–10 m away from vehicle paths and about 100 m apart. Each trap was moved rotatingly until all traps were exposed to each of the five sites. Traps were emptied each morning after 24 h and the tsetse sorted according to species and sex. The data on the different trap catches were analysed using the one-way ANOVA and the multiple range test via the SPSS statistical package. The performance of the Nitse I on G. tachinoides in one area with high tsetse density was significantly better than that of each of the three traps. But for G. m. submorsitans, Nitse I and the biconical trap performed better than only the F3 (P ≤ 0.05) in the high density area. Only the biconical performed significantly better than the F3 trap in an area with low tsetse density. The new Nitse trap was more effective for G. tachinoides than for G. m. submorsitans.