The taxonomy of three species of Smicronyx that are potential biocontrol agents of witchweeds (Striga spp.) in West Africa is revised. The two most abundant species are identified as Smicronyx(Afrosmicronyx) umbrinus Hustache and S. (Smicronyx) guineanus Voss. A third species is described as Smicronyx (Afrosmicronyx) dorsomaculatus Cox, sp. n. Diagnostic descriptions and a key, to separate adults of the three species from each other and from Sharpia bella Faust, are presented. Mature larvae of the three Smicronyx species are separated through a key and diagnoses. A lectotype is selected for Smicronyx umbrinus. All available host and distribution data are summarized for each species.

In the Esmeraldas focus of onchocerciasis in Ecuador, the larvae of the primary vector Simulium exiguum Roubaud are found in sympatry with the non-vector S. gonzalezi Vargas & Díaz Nájera. Distinguishing the pre-ultimate stage larvae of these two species usually relies on the pattern of markings on the cephalic apotome. These patterns appear either as dark spots against a pale cuticle (positive head pattern) or as pale spots within a darkened area of the cuticle (negative head pattern). Larvae of S. exiguum s.l. usually exhibit positive or no head patterns whilst those of S. gonzalezi usually have negative head patterns. The purpose of this paper was to investigate head pattern variation (scored in one of six categories) in (polytene) chromosomally identified larvae of the two species and cytotypes of S. exiguum from three collection sites in Ecuador (including one in the onchocerciasis focus). The head patterns of a total of 1183 larvae were studied. Chromosomal identification of penultimate instar larvae revealed only the presence of the Cayapa and Quevedo cytotypes of S. exiguum (n=208). Both cytotypes exhibited a wide range of head patterns from positive to negative. The results indicate that negative head patterns cannot be used to reliably distinguish between larvae of S. exiguum s.l. and S. gonzalezi. All except one larva with negative head patterns were females (n=53), suggesting that head pattern in this species complex might be a sex-linked character.

What has previously been referred to in the literature as the African white rice borer Maliarpha separatella, is a complex of three closely related stemborers. These are described and the genus revised. The genera Biafra Ragonot and Ethitropa Hampson are synonymized with Maliarpha Ragonot. All primary types available have been examined. The revised genus Maliarpha is a monophyletic group defined by the apomorphic, tri-lobed form of the male gnathos. Six species of Maliarpha are treated, of which brunnella, fuscicostella and longisignumella are described as new. The species Biafra rhodinella (Ragonot), Singhalia haemocharis (Meyrick), Ethiotropa phromerella (Hampson) and Biafra taxiarcha Meyrick are synonymized with Maliarpha concinnella (Ragonot), and Biafra concinnella Ragonot and Saluria rosella (Hampson) are recombined with Maliarpha. The adult moths are illustrated and line drawings of the genitalia are provided for all species.

The dung fly Neomyia cornicina (Fabricius) fed on either control dung or dung containing 0.15 μg g−1 ivermectin were mated in the following combinations: (a) control male × control female, (b) control male × ivermectin-fed female, (c) ivermectin-fed male × invermectin-fed female and (d) ivermectin-fed male × control female. Frequency and duration of mating attempts by males during 10 min mating trials were significantly higher when males were placed with control females, irrespective of male treatment. There was no significant difference between groups in the frequency and duration of all other behaviours observed. There was a significant effect of mating combination on the percentage of females that laid eggs, with most laying in groups where females were controls (groups a and d). There was also significant effect of mating combination on the time to first oviposition, with control females mated with control males (group a) laying earliest. Egg batch size was unaffected by treatment group. At the end of the experiment, all females were dissected and the number, size and yolk content of the terminal oocytes were measured. There was no effect of treatment group on any of these parameters. Results of this study indicate that female exposure to ivermectin was of greater importance than male exposure in altering male mating behaviour and reducing fecundity. Ivermectin in cattle dung could therefore lower reproductive output of this species even when only one of a pair was exposed to the drug.

Delphacodes kuscheli Fennah is the vector of maize rough dwarf virus, that affects maize production in central Argentina. The spatial and temporal abundance pattern of the insect vector was studied from October 1992 to November 1994, within endemic and non-endemic areas of the crop disease. Insect density was estimated every 7–15 days during spring and summer (maize season) or monthly during autumn and winter from high (6 m) and low (1.5 m) sticky traps placed at eight sampling stations along a 300 km transect. Each year, D. kuscheli density increased from October, peaked in December, to decrease afterwards and disappear in May. Density was lower in the nonendemic area and higher in the endemic one. The average absolute difference of density between sampling station pairs increased with the distance between the sampling stations (R2=0.85), and the correlation of density changes decreased with the distance between the sampling stations (R2=0.78), suggesting that the population dynamics were affected more by local than by regional factors. There was a significant correlation (with a 36 days lag) between the normalized difference vegetation index (NDVI) (calculated from 15 days maximum value composites images of NOAA-11 meteorological satellites) and D. kuscheli abundance. Based on this regression model, and using the time series of the satellite derived NDVI values, maps of the distribution and abundance of D. kuscheli within the study area for the spring and summer of 1992 were produced.

The seasonal variation of adult populations of Haematobia irritans Linnaeus was monitored at Santa Fe, Argentina from August 1992 to August 1994 by weekly counts of flies on grazing heifers. Each year, flies were recorded at a density of more than two flies per heifer from August/September to the following June, with peaks of abundance in mid to late spring and late summer to mid autumn. The seasonal trend of fly numbers was best correlated with the mean temperature 4 weeks prior to each fly count (correlation indices of P<0.01 in six of the nine fly periods) followed by the previous 4 week mean saturation deficit. Rainfall and relative humidity correlated poorly with the seasonality of H. irritans. Temperature appeared crucial at the beginning (late winter) and at the end (early-mid autumn) of the fly season while its relevance diminished in the middle of the season. The percentage of heifers that were infested decreased from 80–100% in the fly season to 0–55% between fly seasons but H. irritans never disappeared from the heards, indicating that if diapause occurs at the latitude of the study area, part of the fly population was not sensitive to diapause inducing factors.

Morphometric studies of allopatric populations of the Cotesia flavipes species complex representing three putative species; C. flavipes Cameron, C. sesamiae (Cameron) and C. chilonis (Matsumura), were conducted. Sixteen characters were measured. Principal component analysis separated the complex into three somewhat overlapping groups that corresponded well with previous concepts of the species. Canonical variate analysis separated the complex into three distinct clusters with populations from Africa together, populations from Asia and the Neotropics forming a second cluster, and material from China and Japan forming a third cluster. The Mahalanobis squared distances between the three clusters were nearly equal. Results support recognition of three species in the C. flavipes complex.

Gene diversity and gene flow in Glossina pallidipes Austen were studied by using allozyme electrophoresis on samples from southern and East Africa. Recorded were 30 alleles segregating at eight loci. Gene diversity was 0.212±0.085 S.E. in four southern African populations and 0.163±0.076 in seven Kenyan populations. All loci were in Hardy-Weinberg equilibrium. Pgm and 6pgd were sex linked. Spatial components of gene diversity were measured by using F statistics. Mating was random within each population. The ‘fixation index’ FST was 0.133±0.062 among southern African populations. Among the Kenyan populations. FST was 0.159±0.069. FST was 0.238±0.051 among all populations. Analysis of variance of gene frequencies showed that 65.8% of the genetic variance lay within populations and 34.2% of the genetic variance lay between Kenyan and southern African populations. These data suggest a strong measure of genetic drift among tsetse populations even in a region where it is thought they are continuously distributed. The causes of this drift require investigation.

Larvae of the pine beauty moth Panolis flammae (Denis & Schiffermüller) were reared in sleeve cages on five different seed origins (provenances) of pole stage Pinus contorta in the field in each of four years from 1985 to 1988. Survival varied significantly between the years. In those years when survival was high, Significant differences between tree provenance were not found. However, between provenance significant differences were found in larval weight and stage of development. In the years when survival was low, the results seen in good years were reversed. significant differences attributable to provenance were found but these were not reflected in significant differences between larval weight or development. In addition, there was a significant correlation between the proportion surviving and larval weight, which was not the case in those years where larval survival was high. The results are discussed in light of the pest status of P. flammea in Britain and in view of current silvicultural policies. The use of trees resistant to insect attack as part of an integrated pest management programme is highlighted and the need to coordinate laboratory and field studies so as to control for environmental variation discussed.

The acceptance of different provenances or seed origins of lodgepole pine Pinus contorta and Scots pine P. sylvestris as suitable oviposition sites was found to vary as a function of both tree age and insect species. Experiments on seedling lodgepole pine revealed that the pine sawfly, Neodiprion sertifer Geoffroy (Hymenoptera: Diprionidae), and the larch bud moth, Zeiraphera diniana Guennée (Lepidoptera: Tortricidae), preferred more southerly provenances of lodgepole pine. The pine beauty moth, Panolis flammea Denis & Schiffermüller (Lepidoptera: Noctuidae), however, preferred more northerly provenances. On mature lodgepole pine however, P. flammea exhibited a host change, preferring the more southerly provenances. Neodiprion sertifer showed a similar preference on both seedling and mature provenances. The results of this study suggest that some provenances of lodgepole pine become more resistant to attack by P. flammea as they mature, while others become more susceptible. This may be related to the feeding, strategies of the two insects: P. flammea larvae feed on current year foliage while N. sertifer feeds only on previous year foliage. It is possible that the mechanism for chemical defence of new shoots changes as the trees mature, and to a varying degree in different provenances, while defence of the previous years foliage remains unchanged. Results also indicate that odour alone as opposed to odour plus visual stimulation may invoke different ovipositional behaviour in N. sertifer.

The effect of various infestation levels of Chilo partellus Swinhoe on resistant and susceptible sorghum genotypes was assessed under artificial infestation in two field trials, conducted over two seasons. In the first season, infestation levels were 0, 10, 20, 40, 60 and 80 larvae per 2 m plot row. In the second season, additional treatments of one and two larvae per plot were included. A series of all infestation levels on susceptible plants was also included with an insecticide application 5 days after inoculation. Non-linear relationships between infestation level and yield loss were observed. In susceptible plants, small increases in initial larval infestation levels resulted in sharp increases in yield loss. An opposite tendency was observed in resistant plants where a tolerant reaction at lower infestation levels was observed. Gain threshold (GT) value, indicating the yield increase necessary to compensate for control costs, economic injury level (EIL) and economic threshold level (ETL) at which control actions should be initiated were determined for each genotype. Insecticide application on susceptible plants resulted in a 10% reduction in yield loss. However, the yield was still less than that of unsprayed resistant plants. The GT values indicated that insecticide application was economically warranted at an ETL of 20% and 2% of plants with visible symptoms of whorl damage, for the resistant and susceptible genotypes respectively.

Gel electrophoresis was used to study isoenzyme variation in Panolis flammea Denis Schiffermüller from a total of eight forest sites in England and Scotland dominated by either Scots or lodgepole pine. Four polymorphic loci (esterase, malate dehydrogenase, isocitrate dehydrogenase and 6-phosphogluconate dehydrogenase) were examined in adult moths. Most of the genotype frequencies conformed to Hardy-Weinberg expectations. An estimate of standardized gene frequency variance (Fst=0.109 ±0.032) indicated that there was significant genetic differentitation between populations. There was in addition a latitudinal cline in allele frequency at the 6-phosphogluconate dehydrogenase locus. The possible role of variation between P. flammea populations in contributing to regional differences in pest status is briefly discussed.