Populations of California red scale, Aonidiella aurantii (Maskell), in the eastern Cape Province of South Africa acquired operational resistance to organophosphates in 1984, nine years after resistance occurred in the Transvaal. A bio-assay comparing the efficacies of chlorpyrifos, methidathion, prothiofos, parathion and phenthoate at 0,053 of their field dosages was conducted using resistant red scale crawlers. The results showed that the crawlers were resistant to all these organophosphates as had been found in the Transvaal in 1976.
Scanning electron micrographs of 13 species of four tribes of Cetoniinae, Goliathini, Cetoniini, Diplognathini and Cremastocheilini, illustrate the variations in chorion patterns on the eggs. The significance of these variations is discussed in relation to the egg-laying and development requirements of different species. The differences in chorion patterns do not correspond to the taxonomic groupings of the species.
Population censuses of the Florida wax scale, Ceroplastes floridensis Comstock (Homoptera: Coccidae), and parasites attacking it were made over a 4-year period between 1983 and 1987 in 2 citrus groves in Israel. Two annual generations of the scale were produced in both groves. The most abundant parasite was Tetrastichus ceroplastae Girault (Hymenoptera: Eulophidae). Peak numbers of parasites were synchronized with peak numbers of hosts susceptible to parasitism. Parasites had a significant effect on the host population in one grove, as determined by life-table analysis.
Adult and nymphal material of Afroptilum sudafricanum (Lestage) from South Africa was compared with that of A. montanum (Kimmins) from East Africa. No consistent differences between the two could be demonstrated. A. montanum is therefore treated as a synonym of A. sudafricanum. Notes are given on the distribution of this species in highland areas of East Africa.
Until recently, South African avocados have had relatively few and unimportant insect pests. In Annecke & Moran's (1982) comprehensive review of the insect and mite pests of cultivated plants in South Africa, only five sporadic pests are mentioned and only greenhouse thrips, Heliothrips haemorrhoidalis (Bouche) and red-banded thrips, Selenothrips rubrocinctus (Giard), are discussed in any detail.
The possibility of ageing Locusta migratoria migratorioides (R. & F.) adults developing under winter conditions in the field and laboratory was investigated. Cuticular lamellae in sectioned hind tibae were deposited on a regular daily basis but became reduced in thickness under lower temperature conditions. Using thin stained tibia sections it was found that ages could be confidently estimated for up to 30 days. Results were checked by using field reared locusts of known age.
An emergence of Quintillia cf. vitripennis Karsch (Homoptera: Cicadidae) at Tierberg, near Prince Albert, Cape Province, was observed during September 1990. The density of cicadas was estimated at 376,6 ï¿½ 156 (S.D.) and biomass ca 0,059 kg ha -1. Male cicadas called from stations on the ground and seldom from perches on shrubs. A single instance of oviposition on a Galenia fruticosa (L.f.) Sond. twig was observed.
The colonisation sites of three exotic bark beetle species were determined using buried and partially-buried pine logs placed vertically in the soil. Four trials of increasing complexity were conducted over four seasons within a mature plantation of Pinus radiata D. Don. Almost all (98%) Orthotomicus erosus (Wollaston) were found in the protruding parts of the logs, while most (86%) Hylurgus ligniperda (Fabricius) occurred below soil level.
Pitfall trapping conducted along a road passing through a mosaic of different soil and vegetation types in Mkuzi Game Reserve, Natal, showed that soil type was the most important habitat determinant for Aliogymnopleurus thalassinus Klug and A. consocius Pï¿½ringuey, with aggregation occurring in sand and self-mulching clay soils respectively. The degree of vegetative cover may be of secondary importance to these species.
Experiments and observations on the effects of calling song are presented. Conspecific calling song was found to attract females in Pycna semiclara and both sexes in Azanicada zuluensis. In five species calling song provoked silent males to begin calling. It is likely that the calling song plays a role in the acquisition of mates in all of the study species, and contributes to the formation and temporal organization of choruses in many of them.
The biology of the armoured ground cricket, Acanthoplus speiseri Brancsik, a pest of maize and sorghum in Zambia, was studied in the field and in the laboratory. A. speiseri fed on a number of grasses and on a single species from each of the families Asteraceae and Solanaceae. The cultivated plants, Zea mays L., and Sorghum vulgare Pers., were also fed upon although no conspicuous concentrations of crickets were found on these plants.
More diversified, stable systems of integrated pest management based on use of pesticides, pest-resistant host plants and biological controls (including genetically altered forms) are needed to counter the evolution of highly resistant arthropod pests which attack crops, humans and other animals. To date, resistance has been more common to pesticides than resistant host plants or biological control agents, but examples from each group are well documented. These resistances are due to similar ecological genetic processes, but there are some differences among each pest control class.
New distribution records and comments on the biology and morphology of 19 species of Afrotropical hemerobiids are given. The male genitalia of the genus Anapsectra Tjeder, 1975 are descriptionbed for the first time, and the validity of the genus Dyshemerobius Tjeder, 1961 is discussed. Micromus acutipennis Kimmins, 1956 is recorded for the second time, and Anapsectra berothoide, Dyshemerobius anomalus, and Micromus berzosai are descriptionbed as new species.