African Entomology - Volume 4, Issue 2, 1996
Volumes & issues
Volume 4, Issue 2, 1996
Resource manipulation through architectural modification of the host plant by a gall-forming weevil Urodontus scholtzi Louw (Coleoptera: Anthribidae)Author S.** Price, P.W.* & LouwSource: African Entomology 4, pp 103 –110 (1996)More Less
The manner in which a gall-inducing weevil, Urodontus scholtzi Louw, influences the growth pattern of its host plant, Galenia africana (Aizoaceae), was studied in Namaqualand, South Africa. Galled stems increased by twice the diameter relative to paired ungalled stems in the first and second years and by more than three times in the third year after galling. Stems opposite or distal to the galled stem frequently died, reaching 54 % mortality of opposite stems after one year and over 80 % after three years. Although the weevils have a two-year life cycle, the dominance of galled stems persists for at least four years and probably indefinitely. Resources are manipulated by the weevil when first instar larvae cut partially through vascular tissue, and by an unknown method of creating a strong sink for resources flowing up the stem. Survival in the gall was remarkably high at all sites, with 84-75 % of galls containing adult weevils.
First record of Leptorhaconotus Granger (Hymenoptera: Braconidae) from South Africa, with the description of a remarkable new species and a discussion of the subfamilial placement of the genusAuthor D.L.J. QuickeSource: African Entomology 4, pp 111 –116 (1996)More Less
Leptorhaconotus marshi sp. n. from South Africa is descriptionbed and illustrated. This is the first record of the genus beyond Madagascar. The new species is unique in that the ovipositor sheaths are broadened and fused along the midline to form a flag-like appendage that does not cover the ovipositor. The systematic placement of Leptorhaconotus Granger is discussed on the basis of new data on ovipositor structure and internal anatomy.
Suitability of Metriona elatior (Klug) (Coleoptera: Chrysomelidae: Cassidinae) as a biological control agent for Solanum sisymbriifolium Lam. (Solanaceae)Author P.E. HiII, M.P. & HulleySource: African Entomology 4, pp 117 –123 (1996)More Less
A leaf-feeding tortoise beetle, Metriona elatior (Klug), was screened as a biological control agent for the weed Solanum sisymbriifolium Lam. in South Africa. Favourable biological characteristics of M. elatior include a high reproductive capacity, long-lived adults and several generations per year under laboratory conditions. Host range was investigated by larval survival, and host plant choice tests by adults. Larvae were successfully reared on 10 of 11native Solanum species tested, five exotic Solanum species (except S. sisymbriifolium) and on the economically important eggplant, S. melongena L. The adult females selected these native and exotic Solanum species, and eggplant as suitable for oviposition. Based on these results it was decided not to apply for release of this insect.
Author J. IrishSource: African Entomology 4, pp 125 –129 (1996)More Less
The status of the previously misidentified Damarus singularis peringuey was clarified by examination of the syntypes. A second Damarus species is descriptionbed, and a key to the species is provided. The rudimentary distribution records hitherto available are supplemented by additional material, and are illustrated in two maps.
Biological studies of Xanthopimpla stemmator (Thunberg) (Hymenoptera: Ichneumonidae), a parasitoid of lepidopteran stem borersAuthor Rami Moore, S.D. & KfirSource: African Entomology 4, pp 131 –136 (1996)More Less
The solitary pupal endoparasitoid, Xanthvpimpla stemmator (Thunberg), was introduced into South Africa from Mauritius as a biological control agent of lepidopteran stem borers of grain crops and sugarcane. The biology of the parasitoid was studied in the laboratory. The mean pre-oviposition period of females was five days and oviposition period 64 days. Each female produced a mean of 95 offspring, with females comprising 64 % of the progeny. There was a significant correlation between density of parent population and sex ratio of offspring, the greater the density the higher the percentage of female offspring. Minimum threshold temperature for development was 11.44 C and thermal constant 248.2 day-degrees. Females lived longer than males and the presence of hosts shortened the life of both sexes. The stem borers Chilo partellus (Swinhoe) and Eldnna saccharina Walker were suitable hosts for X. stemmator whereas the bollworm Helicoverpa armigera (Hubner) was not. Xanthopimpia stemmator was released in maize and grain sorghum fields in the Transvaal during four growing-seasons between 1987 and 1993. A few recoveries of parasitoids were made from the release sites, but X. stemmator failed to establish itself. The potential of X. stemmator as a biocontrol agent of lepidopteran stem borers in South Africa is discussed.
A new genus and species of Buprestidae (Coleoptera) from the Namibian Richtersveld, with comments on the relationships of the subtribe Mastogeniina LeConte & HornAuthor C.L. BellamySource: African Entomology 4, pp 137 –142 (1996)More Less
A new buprestid genus and species, Namibogenius confusus, belonging to the subtribe Mastogeniina (Buprestinae: Thrincopygini) is descriptionbed from the Richtersveld of southern Namibia. The genus is discussed relative to others from Africa, with comments regarding the placement of this subtribe in the familial hierarchy.
Ecological aspects of pitbuilding and non-pitbuilding antlions (Neuroptera: Myrmeleontidae) in the KalahariSource: African Entomology 4, pp 143 –152 (1996)More Less
The spatial distribution of the pitbuilding antlion Cueta sp., and the non-pitbuilders Furgella intermedia Markl and Palpares annulatus Stitz was correlated with environmental temperatures, prey abundance and vegetation, over six seasons from 1990-1992. Antlion larvae in the Kalahari migrated vertically in the sand at high sand-surface temperatures. They restricted their activity to the cooler parts of the day and were more abundant in the shade than in sunny areas. These behavioural patterns were similar to those reported for antlion species living in cooler regions. It is suggested that the depth to which the antlion larvae migrated is dependent upon prevailing environmental conditions. At high sand temperatures no differences were found between the vertical migration patterns of pitbuilders and non-pitbuilders. Prey densities and richness fluctuated between the different seasons. It is suggested that overlap in microhabitat (preference for shade) and activity patterns of antlion larvae and their prey, enhance prey capture in myrmeleontid larvae.
The genus Comperiella Howard (Hymenoptera: Encyrtidae) in southern Africa: parasitoids of armoured scale insects (Homoptera: Diaspididae)Author G.L. PrinslooSource: African Entomology 4, pp 153 –160 (1996)More Less
The southern African species of the encyrtid genus Comperiella Howard are reviewed. Two new species, C. apoda and C. karoo, are descriptionbed while C. eugeniae (Rishee) is synonymized with C. bifaseiata Howard, and C. lemniscata Compere & Annecke is recorded from the region for the first time. A key is provided to distinguish females of the nine known species of Comperiella, five of which occur in southern Africa.
An evaluation of the pest status and research conducted on phytophagous Lepidoptera on cultivated plants in South AfricaAuthor M.A. Bell, J.C. & McGeochSource: African Entomology 4, pp 161 –170 (1996)More Less
A literature survey was conducted on Lepidoptera that damage cultivated plants in South Africa, to estimate the present status of local lepidopteran pests and to highlight research priorities. A database was compiled from papers published between 1980 and 1994. Moran's (1983) formula for determining pest status was modified to provide a more objective assessment of the relative importance of the pest species. Helicoverpa armigera (Hubner) ranks as the most important lepidopteran pest in South Africa. The pest status of Eldana saccharina Walker Tortrix capensana (Walker) and Chilo partellus (Swinhoe) ranked higher than in Moran's (1983) assessment, whereas the pest status of Plutella xylostella (Linnaeus) ranked substantially lower. Following global trends, the Noctuidae were found to be the most important lepidopteran pests in South Africa, and cosmopolitan and African lepidopteran pests were of greater importance than endemic species. Borers and cutworms were more important than defoliators and miners. Articles relating to extension services exceeded research papers, and 28 % of research publications appeared in international journals. The output was greatest on citrus and cereal crops, and the Institute for Tropical and Subtropical Crops published the most articles on lepidopteran pests during the period reviewed. A substantial amount of information on the control of lepidopteran pests in South Africa has been published, whereas only a few articles on yield loss, economic loss or pest distributions have appeared. Studies of yield loss and economic loss will improve the efficiency of pest management practices and will also facilitate the calculation of true pest status, and are identified as research priorities. The descriptionption and monitoring of pest distributions are also important in anticipating and mitigating the potential negative impact of climate change on agroecosystems.
Miteronotus, a new genus with four new species from South Africa (Heteroptera: Aradidae: Carventinae)Author D.H. JacobsSource: African Entomology 4, pp 171 –188 (1996)More Less
Miteronotus gen. n. containing four new species, M. labeosus, M. bucculentus, M. viginti and M. knysnaensis, is descriptionbed and illustrated. The species are descriptionbed, illustrated and compared and their chromosome numbers are given. A key to the species is provided.
The effect of food plants on metabolic reserves, development and fecundity in the African pest grasshopper. Zonocerus variegatus (Linnaeus) (Orthoptera: Pyrgomorphidae)Author G.F. Modder, W.W.D & TamuSource: African Entomology 4, pp 189 –196 (1996)More Less
Groups of Zonocerus variegatus were placed in cages with food plants. Sixth instar nymphs were supplied with a mixed diet of Manihot esculenta, Vernonia amygdalina and Chromolaena odorata, and a single sample of each of these and Acalypha wilkesiana. The highest growth rate, the most haemolymph and fat body, and the greatest food value in these tissues (carbohydrates, proteins and lipids), were generally found in those grasshoppers fed on the mixed diet and those fed on M. esculenta. Grasshoppers fed on A. wilkesiana and V. amygdalina mostly yielded intermediate, and those on C. odorata the lowest values. Instar duration lasted twice as long on C. odarata. Mixtures of Synedrella nodiflora, C. odorata and Paullinia pinnata, and each of these plus M. esculenta and A. witkesiana, were tested singly on the adults. The best somatic growth was manifest by adult females fed on M. esculenta and A. wilkesiana, and the poorest on C. odorata. On S. nodiflora and the mixture, growth was intermediate. The pre-oviposition period was shortest on M. esculenta and longest on S. nodiflora. The ovaries did not develop on C. odorata and P. pinnata. In late vitellogenesis, the largest ovarioles, containing the most reserves, were found in adult females fed on M. esculenta, and the smallest on S. nodiflora. On A. wilkesiana and the mixture, these were intermediate. Most eggs were produced on M. esculenta, but egg-pod length was constant irrespective of food plant. It was concluded that a mixed diet, even of relatively poor plants, is generally more beneficial than single food plants.
A new species of the worm lion genus Vermilynx Stuckenberg (Diptera: Vermileonidae) from Namaqualand, South AfricaAuthor B.A. StuckenbergSource: African Entomology 4, pp 197 –202 (1996)More Less
The distinctive species Vermilynx jasoni sp. n. is descriptionbed from the Springbok District of Namaqualand. Sexual dimorphism in antennal form is confirmed as a generic feature of Vermilynx; the female antenna shows an early stage in the evolution of a stylus. A suite of autapomorphies is descriptionbed for the genus. A possible association of Vermilynx with the Nama Highlands is mooted, and ecological features of the type locality are descriptionbed.
Author H.E. Chown, S.L. & SteenkampSource: African Entomology 4, pp 203 –212 (1996)More Less
It has been argued that the strength of the relationship between body size and abundance in local assemblages can be predicted from both the number of species included in a study and the extent of their size range; that transient species do not alter the statistics of this relationship; and that the optimal or modal size for a given assemblage can be predicted from a model using the constants and exponents of the allometric relationships between body mass and resource acquisition, and body mass and resource conversion to offspring. Data on the body size and abundances of scarabaeine dung beetles from an arid, southern African savanna habitat, sampled over a 16-month period, and on the scaling of metabolic rate and population growth in insects, were used to examine these hypotheses. Coefficients of determination for the abundance: body size relationship were within the range expected from the sample size and size range of the assemblage when transient species were excluded. When transients were included the fit was poorer Transient species had a lower abundance than the resident species, but no difference in body size between the two groups was found. The mode of the species-body size frequency distribution was not predicted by the model when the required parameter values were obtained from the relationship between exact rates of increase (rm) and body mass (resource acquisition), and metabolic rate and body mass.
New and little-known South African Meligethes Stephens of the M. convexus group (Coleoptera: Nitidulidae: Meligethinae)Author P. AudisioSource: African Entomology 4, pp 213 –230 (1996)More Less
The known South African species of the convexus species group in the genus Meligethes Stephens are revised. Four new species are descriptionbed from South Africa and Botswana: Meligethes becivorus, M. byrrhoides, M. oberprieleri and M. paraconvexus. Meligethes gibbulus. Spornraft & Kirejtshuk and M. xyphosuroides Kirejtshuk are transferred from the subgenus Lariopsis Kirejtshuk to the M. convexus species group. Meligethes pallipes Boheman is removed from the M. convexus species group and provisionally placed in the unrelated M. aethiopicus Grouvelle species group. edescriptionptions and illustrations of male and female genitalia, legs and habitus of M. convexus Boheman, M. subglobosus Reitter and M. accretus Kirejtshuk, and ecological data on most of the species are included. Meligethes atomus Grouvelle, previously known only from Tanzania, is a new record from southern Africa, and a new synonym, Meligethes Qtomus Grouvelle, 1904 Meligethes johnsi Easton, 1960, is established.