Sperm are transferred from male to female tsetse, as in most insect species, within a spermatophore. The spermatophore of the tsetse species, Glossina morsitans morsitans Westwood (Diptera: Glossinidae), is highly organized, and can be visualized as a sac deposited in the uterus of the female tsetse. The wall of the spermatophore comprises two layers, whose components are strikingly similar to those of the secretions made by the male accessory reproductive glands. Dense aggregates of material, matrix filaments, and clusters of granules predominate in both. An ultrastructural study of these components is reported in this paper.

Studies were carried out in 1983 to determine the relative abundance and species composition of three lepidopterous stem borers in upland and irrigated rice at Ibadan, southwestern Nigeria. The relationship between irrigated rice crop phenology and the population of the borers and stalk-eyed fly was also studied.

White stem borer, Maliarpha separatella was the predominant species in upland and irrigated rice, followed in upland rice by pink stem borer, Sesamia calamistis, and striped stem borer, Chilo zacconius and in irrigated rice by C. zacconius and S. calamistis. The proportion of M. separatella was higher in irrigated rice than upland. Three population peaks were observed annually in both upland and irrigated rice.

Studies on the relationship between irrigated rice phenology and field population of lepidopterous borers and a dipteran borer showed that the stalk-eyed fly, Diopsis spp., occurred before 20 days after transplanting (DAT) in ITA 212 and continued up to 90 DAT: the peak was observed at 40 DAT. The lepidopterous borers did not appear until 40 DAT and populations peaked at 80 DAT.

A South American leaf galling psyllid, Calophya schini Tuthill, has recently been discovered attacking the South American tree Schinus molle L. in Kenya and Ethiopia. This represents the first record of the psyllid in each country and the only record of C. schini in Africa outside of South Africa. In Kenya, the psyllid was parasitized by an unidentified tetrastichine (Eulophidae), probably of the genus Tamarixia, while in Ethiopia C. schini nymphs were heavily parasitized by an unidentified hymenopteran.

Scirtothrips dorsalis Hood is a polyphagous species and an important sucking pest of tea (Camellia sinensis) (Theaceae). The fitness traits of S. dorsalis on two alternative host plants: Capsicum annuum L. (chilli) (Solanaceae) and Ricinus communis (castor oil plant) (Euphorbiaceae) and on C. sinensis and corresponding levels of defence enzymes was studied. The study revealed that C. sinensis is the more suitable host of S. dorsalis based on faster development (13.6 days) compared to the alternative hosts, C. annuum (15.5 days) and R. communis (16.7 days), a higher fecundity (C. sinensis: 11.4 eggs; C. annuum: 9.7 eggs; R. communis: 8.6 eggs), and superior egg hatchability (C. sinensis, 92.6%; C. annuum: 82.5%; and R. communis: 74.6%). The host-based variation in the fitness traits of S. dorsalis corroborated in light of differential activity of three major detoxifying enzymes, such as the general esterases (GEs), glutathione S-transferases (GSTs), and cytochrome P450 mediated monooxygenases (CYPs). Densitometric analysis of GEs showed five esterase isozymes (EST I–V) with retardation factor (Rf) values of 0.17, 0.22, 0.27, 0.35 and 0.52, respectively. The pixel density, and accordingly the profile height, varied in different host-specific S. dorsalis. A significant variation of the quantity of these enzymes was also apparent in the insect when reared on the three hosts. A 2.4 and 2.7, 1.6 and 2.0, and 2.0 and 2.3-fold higher GEs, GSTs and CYPs activity on the two non-tea hosts possibly signify a predisposition of the species for higher tolerance to insecticides, enabling the pest to switch to tea where synthetic insecticides are routinely used.

The nature, number, structure and behaviour of chromosomes during the meiotic and mitotic sequences in the armoured ground cricket, Acanthoplus speiseri Brancsik, were investigated from testicular and ovariole material. The karyotype of A. speiseri is 2n ♂=25 (24 autosomes + XO) and 2n ♀=26 (24 autosomes + XX). The species exhibits the primitive XO ♂ /XX ♀ type of sex determination mechanism. All chromosomes in the cell complement (including the X sex chromosome), in both sexes, are acrocentric in shape. The X sex chromosome is the largest element in the karyotype while the autosomes comprise three large, four medium and five small pairs. The behaviour of the chromosomes during the meiotic and mitotic processes is normal and typically orthopteran. The study discusses the important role that karyology and cytogenetics can play for species diagnostics in the subfamily Hetrodinae.

Stenogiffardia Evans, 1977 is considered the senior synonym of Pratura Theron, 1982 syn. nov. and Doraturella Emeljanov, 2002 syn. nov., resulting in four new combinations. Duraturopsis Melichar, 1908 syn. nov. is considered a junior synonym of Chiasmus Mulsant and Rey, 1855, resulting in one new combination. Figures of the ovipositor of Stenogiffardia parvula (Kirkaldy) are provided for the first time, and habitus images of S. parvula and Chiasmus katonae (Melichar) comb. nov. are provided.

Sweetpotato weevil, Cylas formicarius formicarius F is the most destructive pest of sweetpotato, Ipomoea batatas in tropical and subtropical regions. The larvae and adults feed on sweetpotato roots and crowns. For the past 12 years we have been screening sweetpotato germplasm for resistance to this pest in order to breed an agronomic cultivar with weevil resistance. Resistance screening is conducted at AVRDC and Penghu island in autumn and summer, respectively. Germplasm is planted between heavily infested source rows maintained in a weevil nursery. Roots are harvested, sliced into thin pieces, and the number of insects (larvae + pupae + adults) per unit weight, as well as the weight of damaged and healthy root slices, are recorded. The resistance rating is based mainly on the number of insects found in the root. Considerable differences in resistance rating are observed from location to location and season to season. Even at one location, tremendous differences are observed in weevil infestation of a particular entry among the replicates. Although over 1000 sweetpotato accessions have been screened, we have not found any that is consistently less damaged over several seasons at either location. Our recent screening of a population of I. trifida × I. batatas crosses show certain hybrids with high yield and low weevil infestation. These hybrids need to be evaluated further to confirm their resistance.

The southwestern corn borer, Diatraea grandiosella, has expanded its range during this century so that it is now distributed between about 18 and 38°N latitude in Mexico and the United States. The species survives from year to year by entering a facultative larval diapause, and over most of its range it is bivoltine or trivoltine. Fully grown pre-diapausing larvae prepare an overwintering cell in the stalk crown of their host plant, typically maize, and then ecdyse from a spotted to a pigment-free morph at the onset of diapause. Southwestern corn borers originally obtained from southcentral Mexico (19°N latitude) and the United States (33–38°N latitude) were reared on an artificial diet under standardized conditions to compare several of their life history traits. Information is presented about voltinism, photoperiodic responses, growth and reproduction, larval behaviour and ecdyses, and the diapause-associated protein in an attempt to evaluate characteristics that have enabled the species to disperse from a tropical to a temperate region.

Tomatoes, an important tropical crop, suffer greatly from various plant viruses which are transmitted by the tobacco (sweetpotato) whitefly, Bemisia tabaci. Since these viruses cannot be controlled directly, the only path available to the grower is to prevent their transmission. The shortcomings of chemical control are well known and the use of alternative control methods is limited. Consequently, resistant cultivars would be the best solution for the grower. Breeding for resistance to the whiteflies as vectors of viruses has some clear advantages compared with breeding plants resistant to the virus. In search for sources of resistance among wild tomatoes, the two most resistant accessions of Lycopersicon pennella, L. hirsutum and L. hirsutum f. glabratum were selected. Although these accessions are susceptible to the virus, in the field they were only slightly, or not, infested. The resistance of L. pennella was found to be based entirely on the sticky material which is exuded by glandular trichomes located on the leaves and stems. The rate of resistance depends partially on environmental factors like photoperiod and light intensity. A reliable method for quantitative detection of resistance in L. pennella was developed.

Observation on the distribution and seasonal variation of riverine tsetse population at Egbe in the Derived Savanna Zone of Nigeria was made and compared with variation in other vegetation types of the country. Egbe, in a sub-humid location, was observed to have a low rainy/high dry season population density similar to what occurs in part of the Southern Guinea Savanna Zone. To the north of these areas, the less humid vegetation zones show a definite reverse pattern (high rainy/low dry season) of seasonal population density. The Rain Forest Belt, a humid zone has, surprisingly, more similarity with the less humid zones to its far north than with the sub-humid zones nearer to it Irrespective of zone and season, a favourable temperature of between 26.1 and 26.7°C appeared important towards having a high population density. Reasons were given for the low rainy season tsetse density at Egbe. Unlike zones in the less humid north where rainy season dispersal is well marked, tsetse distribution in the Derived Savanna Zone remained by the riverine vegetation almost throughout the year. The advantage of this study to a proposed ranch for the area was highlighted.

Gorging is stimulated in some insects by plasma components alone. In other insects engorgement is maximal only when blood cell components are present in addition to the plasma. Plasma components recognized by insects are NaCl, NaHCO3 (some anopheline mosquitoes) and albumin (Anopheles dirus and Pediculus humanus). Those requiring blood cells recognize this fraction by its adenine nucleotides which, for optimal engorgement, have to be offered in the presence of isotonic NaCl solution buffered by NaHCO3 (i.e. Rhodnius, culicine mosquitoes, Simulium, tsetse and Tabanus). The presence of albumin in the feeding medium may lower the level of nucleotides required to induce gorging (i.e. Aedes).

For most haematophagous insects requiring the cellular fraction, ATP is the most effective phagostimulant. It may however be replaced quite effectively by non-hydrolyzable analogues, indicating that ATP is not essential as a source of energy for the gustatory receptors involved in blood meal recognition.

Whole body tick collections, carried out at 6-day intervals for 2 months at Nisheishiba, showed significant differences in tick counts between three breeds of cattle. Crossbred (Bos taurus × B. indicus) cows carried 4.5 times more ticks (mean tick count 70.5 ± 84.8) than the B. indicus Kenana (mean tick count 16.7 ± 24.4) and Butana cows (mean tick count 15.0 ± 18.4). In all cases, the SD's were larger than the means reflecting the usual wide variability in tick numbers between individuals. Significant differences also existed in the degree of engorgement achieved by female Hyalomma anatolicum anatolicum ticks on different breeds of cattle. The weight of detaching fully engorged females feeding on Kenana and crossbred cattle was 374.8 mg and 422.0 mg respectively. This was reflected in the amounts of eggs laid by the females which were 191.3 mg for the Kenana-fed ticks and 261.1 mg for those from the crossbreds. The resulting larval challenge from the crossbred-fed ticks was 36.5% greater than from the ticks fed on Kenana cattle.

A test with 100 nymphs of Hyalomma anatolicum anatolicum for evaluation of resistance of cattle to ticks was found to have a good potential for assessing the resistance status of cattle. Thus, 7% of nymphs engorged and moulted on a resistant host with average engorgement weight of 7.6 mg compared to 19 and 45% of engorged nymphs on two susceptible hosts with 15.8 and 13.6 mg average engorgement weights. Similarly, the number of detached fully engorged Rhipicephalus evertsi nymphs dropped from the resistant cows ranged between 14 and 57 compared with 118–124 from the two susceptible animals. The correlations between the three parameters; ranking cattle for resistance (natural tick burdens), the number of detached fully engorged R. evertsi nymphs, and the percentage survival of H. a. anatolicum nymphs after artificial infestation are discussed and found to be significant (r = +0.778; r = +0.886; r = +0.936). It is, therefore possible to assess the overall resistance status of hosts and cull the susceptible, if necessary.

The influence of host presence, age and mating on calling behaviour of the female spotted bollworm, Earias vittella, was studied under a 14L:10D photoperiod. Onset of calling was earlier in the presence of a host and 93% of the females initiated calling in its presence on day one after emergence, compared to 67% in its absence. A majority of the females initiated calling during the 10th hour of the first scotophase and thereafter the initiation shifted to earlier hours as age advanced. Females generally called longer in the presence of a host. The mean time spent in calling, from the 1st to the 10th day increased from 56 to 152 min in the absence of a host, and from 77 to 234 min in its presence. Most of the females resumed calling after mating, but the mated females exhibited a significant reduction in calling performance when compared with the virgin females.

A one-year survey was carried out in two brackish water pools to study the incidence of Amblyospora sp. in field populations of Culex sitiens larvae at the Kenya coast. Salinity of the pools, water temperature, and rainfall patterns were also recorded to check their possible effects on the infection rates. Levels of infection in both pools were low, and ranged between 2 and 15%. Infections occurred in a wide range of salinity. Statistical analysis (t-test) showed no significant correlation between infection rates and neither salinity, temperature nor rainfall in the field.

The stemborers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) cause the highest economic damage to maize and sorghum in Zimbabwe. A number of studies on stemborer bioecology and management in Zimbabwe have been conducted, but most are still incomplete. The more important of these are studies on life history, incidence and distribution patterns, host plants, yield losses, chemical control, cultural control, host plant resistance, the use of sex pheromones, and biological control. These are discussed here in detail, and areas where further research is needed are pointed out. As part of an integrated strategy for managing stemborers in Zimbabwe, an exotic braconid larval parasitoid, Cotesia flavipes Cameron, has been released in the lowveld area and prospects for its establishment appear to be good. However, this establishment might be curtailed mainly by the inability of Co. flavipes to adapt to the seasonal carryover mechanisms utilised by the indigenous Cotesia sesamiae (Cameron).

The effects of infection by Trypanosoma brucei and DNA virus on the ultrastructure of the salivary gland cells in Glossina pallidipes Austen were investigated. Cytoplasm of uninfected cells contains a dense ribosomal population and rough endopiasmic reticulum, scattered Golgi areas and mitochondria. In infected ceils of salivary glands the ultrastructural integrity of the cytoplasm is profoundly changed due to cellular proliferation giving rise to a stratified epithelium and gland enlargement; cell degeneration characterized by formation of cytoplasmic vacuoles, chromatin margination, disorganization and elimination of cell organelles and gland hypertrophy. The virus particles are found in the nucleoplasm as well as the cytoplasm of cells. The ultrastructural evidence indicates that the virus are largely assembled in nuclei of cells and virions pass through the nuclear membrane. The trypanosomes are found within the degenerating cytoplasm and lumen of the cell.

The implications of the features observed in the infected cells are discussed, and possible suggestions are made regarding alteration of the metabolic functions due to infection.

The differential attraction by 2 pigeonpea cultivars has been tested through the oviposition behaviour of Heliothis armigera females in a standardized laboratory assay. Seedlings of a susceptible variety (PPE-50) are under choice conditions significantly more attractive at a distance, and without contact allowed other than those of the resistant variety (PPE-45). The volatile signal is contained in the hexane extract from PPE-50 leaves, as shown in the oviposition assay, and after vacuum distillation is present in the more volatile fractions of the mono- and sesquiterpenoids. These compounds, which are also contained in the hexane extracts of 2 more pigeonpea cultivars, a check of medium susceptibility (T-21) and a wild relative (Atylosia scarabaeoides), were compared by capillary gas chromatography. The 4 pigeonpea varieties were characterized by their specific aromagrams, a method which may also advantageously be used in pigeonpea breeding programs.

Graminaceous crops are attacked by lepidopterous stem-borers all over the world causing severe crop loss. Chemical control of stem-borers is difficult and biological control is preferable for peasant farming systems. The most important genera are Diatraea, Chilo, Eldana, Sesamia and Busseola. Their natural enemies include egg, larval and pupal parasites and predators. The parasites are cued by different stimuli, some to host plant, others to borer tunnels or frass. Biocontrol was first attempted against Diatraea spp. in the New World where D. saccharalis is now under fair control in several countries. In the Old World attempts have been made to control C. sacchariphagus and E. saccharina without much success. In East Africa releases of exotic parasites against B. fusca, S. calamistis, C. partellus and E. saccharina have not been very successful and further work is suggested. Leguminous crops suffer from attacks of lepidopterous pod-borers. The most damaging species are Etiella zinckenelia, Maruca testulalis, Cydia spp. and Lampides hoeticus. There are relatively few records of important parasites and fewer still of predators, however, large parts of the world are still unsurveyed for natural enemies. Successful control using introduced parasites has been reported from Canada against C. nigricana and Mauritius against E. zinckenelia and M. testulalis. There appears to be scope for introductions of Caribbean parasites into Africa.

The application of nucleic acid hybridization techniques in the identification of most protozoan parasites, using species-specific DNA probes, has recently been described by several investigators. Species-specific DNA probes have been employed in the characterization of trypanosome infections in cattle and tsetse from Uganda. Most infections revealed by our DNA probes were mixed. Using these probes, a mixed infection with Trypanosoma brucei, T. vivax and both savannah and Kilifi types of T. congolense was revealed in one cow. This mixed infection could not have been detected by any of the classical parasitological methods. Isolates made from natural field infections, which had been passaged in laboratory animals, were found to consist of homogeneous trypanosome species. This was demonstrated in all of 47 stabilates which were homogeneous infections either of savannah type T. congolense or T. brucei.

The method of sample preparation for DNA probe analysis was modified to suit field conditions. The samples, which were spot-blotted onto nylon filters and either immediately denatured or left undenatured, could be kept at room temperature for 1 month with only a moderate loss of hybridization signal intensities. Although hybridization signals were visible in undenatured samples, those seen with the samples that had been denatured were clearly more intense. This approach eliminates the need for liquid nitrogen and/or an incubator in the field. The simplicity, sensitivity and specificity of this diagnostic technique using species-specific DNA probes, make it an important tool for future studies of the epidemiology of African trypanosomiases.