African Entomology - Volume 12, Issue 2, 2004
Volumes & issues
Volume 12, Issue 2, 2004
Source: African Entomology 12, pp 157 –163 (2004)More Less
In this study we analysed the theoretical population dynamics of C. megacephala, an exotic blowfly, kept at 25 and 30 °C, using a density-dependent mathematical model, with parametric estimates of survival and fecundity in the laboratory. No change in terms of oscillation patterns was found for the two temperatures. The populations exhibited a two-point limit cycle, i.e. oscillations between two fixed points, at 25 and 30 °C. However, a quantitative change was observed, indicating that at 25 °C the number of immatures in equilibrium is 1176 and at 30 °C, 1944. The implications of this difference in terms of equilibrium for population dynamics of C. megacephala are discussed.
Critical periods of soil pest damage to groundnut in intercropped groundnut / sorghum in northern NigeriaSource: African Entomology 12, pp 165 –170 (2004)More Less
Control of groundnut soil pests is seldom undertaken by resource-poor farmers in Nigeria, mainly due to ignorance of the appropriate control methods or lack of financial resources to purchase the necessary pesticides. In order to recommend to farmers appropriate control periods for the major soil pests of groundnuts and thus minimize cost, field trials were set up in farmers' fields at two sites in the Sudan savanna zone of northern Nigeria in 1996 and 1997 to monitor soil pests. Results showed that the major soil pests were termites, whitegrubs and millipedes. Termite attack on groundnut increased with plant maturity whereas whitegrub and millipede attacks were most critical at the early growth and pod formation stages, respectively. Therefore, resource-poor groundnut farmers in termite- or millipede-endemic areas may achieve some degree of control by applying pesticides at pegging to guard against the critical period of attack on soft or mature pods. In areas where groundnut is more prone to whitegrub attack, pesticide application will be most effective at the early stage of plant growth. Where all three groups of pests threaten groundnut production, a minimum of two pesticide applications, one at early plant growth and the second at pegging, is suggested.
Spatial distribution of lepidopterous stem borers on indigenous host plants in West Africa and its implications for sampling schemesSource: African Entomology 12, pp 171 –178 (2004)More Less
A catalogue of the major indigenous host plants in West Africa of maize stem borers, the noctuids Sesamia calamistis Hampson and Busseola fusca (Fuller) (Lepidoptera : Noctuidae), and the pyralid Eldana saccharina Walker (Lepidoptera : Pyralidae), was established during surveys in Benin, Ghana and the Ivory Coast. Thirteen hosts were identified for S. calamistis, ten for E. saccharina and two for B. fusca. The non-gramineous hosts were the two sedge species, Cyperus papyrus and Rhynchospora corymbosa (Linn.) Britt. C. papyrus was infested by S. calamistis and E. saccharina, and R. corymbosa was infested by S. calamistis only. In general, borer densities were much lower than those reported from maize. For the development of sampling plans, dispersion was described for all species using Taylor's power law and a non-linear model which gives the relationship between the proportion of infested plants [P(I)] and the mean density (m). The majority of host-plant species yielded an aggregated distribution of stem borers, corroborating results of various authors. Mean dispersion was similar among insect species, thus common optimal sample size / mean density curves were developed for all borer species. Enumerative sampling procedures are proposed as binomial sampling plans were shown to be less efficient.
The impact of an invasive ant, Linepithema humile (Mayr), on the dispersal of Phylica pubescens Aiton seeds in South AfricaSource: African Entomology 12, pp 179 –185 (2004)More Less
Myrmecochory, or seed dispersal by ants, is a mutualistic plant-ant interaction common to the fire-prone shrublands of the southwestern Cape, South Africa. Elaiosome-bearing seeds are located rapidly by ants and transported to nests where they are protected from granivorous rodents, desiccation and fire. This interaction is threatened by the invasive Argentine ant, Linepithema humile, which has displaced important myrmecochorous ant species in previously undisturbed areas. The impact of this infestation was assessed. Linepithema humile, which was active mainly at night, dispersed few seeds and removed most of the elaiosomes in situ. The majority of seeds were dispersed from invaded areas during the day by two indigenous species of ants, Tetramorium quadrispinosum and Ocymyrmex cilliei. Dispersal in uninvaded areas occurred mainly between 19:00 and 21:00 but was generally spread over a 24-hour period, indicating the participation of a complex of ant species. Significantly more seeds were dispersed in uninvaded areas than in areas invaded by L. humile. In invaded areas, there were no significant differences in the numbers of seeds dispersed by ants and the numbers eaten by rodents. In contrast, significantly more seeds were dispersed by ants than were eaten by rodents in uninvaded areas.
Colonization of cultivated and indigenous graminaceous host plants by Busseola fusca (Fuller) (Lepidoptera : Noctuidae) and Chilo partellus (Swinhoe) (Lepidoptera : Crambidae) under field conditionsSource: African Entomology 12, pp 187 –199 (2004)More Less
Stem borers are generally polyphagous, attacking cultivated as well as wild host plants. Two field trials, incorporating four cultivated cereal crops and two grass species, were conducted to study colonization of cultivated crops and grasses by stem borers. The first trial consisted of maize (Zea mays L.), sorghum (Sorghum bicolor (L.) Moench), sweet sorghum (Sorghum bicolor (L.) Moench), pearl millet (Pennisetum glaucum (L.) R. Br.), Hyparrhenia tamba (Steud) (blue thatching grass) and, Panicum maximum (Jacq.) (Guinea grass). During the following two seasons P. maximum was replaced by Pennisetum purpureum (Schumach) (Napier grass). In the second trial P. purpureum was replaced by P. maximum. Plots (5 ×5m) were arranged in a 6 × 6 Latin square design. Natural infestation by stem borers was allowed to take place. The stem borers found on host plants were Chilo partellus (Swinhoe) (Lepidoptera : Crambidae) and Busseola fusca (Fuller) (Lepidoptera : Noctuidae). The incidence of whorl damage, dead heart and stem damage observed indicated that all host plants were susceptible to stem borer attack. Cultivated host plants showed higher incidences of whorl and stem damage than the grasses. The low incidence of whorl damage on the grasses may be ascribed to larval antixenosis at the feeding site. Quicker larval development as well as increased size was observed on cultivated crops than on the grasses. The results of this study indicated better colonization of cultivated crops by the stem borers compared with the grasses.
Distribution and aspects of the biology and host range of Eurytoma sp. (Hymenoptera : Eurytomidae), a candidate agent for the biological control of Bryophyllum delagoense (Ecklon & Zeyher) Schinz (Crassulaceae) in AustraliaSource: African Entomology 12, pp 201 –207 (2004)More Less
Surveys were conducted in Madagascar for potential biological control agents for Bryophyllum delagoense (Ecklon & Zeyher) Schinz, an invasive plant in Australia. The phytophagous wasp Eurytoma sp. (Eurytomidae : Eurytominae) was found throughout the natural distribution of its host plant, B. delagoense, in southern Madagascar and was imported into South Africa for life history studies and preliminary host-range testing. The wasp proved to be a suitable candidate agent because it was easy to rear, had multiple generations per year and was damaging to its host plant in the field and under laboratory conditions. Eggs are deposited in the plantlets (bulbils), leaves and/or seedling stems and the larvae complete their development in the plant. There are five larval instars and pupation occurs in excavated pupal chambers within the plant. Adults emerge from plants 5-10 days after pupation and are short-lived. Preliminary host range trials revealed that Eurytoma sp. is oligophagous with larvae being able to complete their development on only three other species in the Crassulaceae. Extensive host range trials still have to be undertaken in Australia before the wasp can be considered for release as a potential biological control agent for B. delagoense.
Effect of crowding on fecundity, body size, developmental time, survival and oviposition of Carcinops pumilio (Erichson) (Coleoptera : Histeridae) under laboratory conditionsSource: African Entomology 12, pp 209 –215 (2004)More Less
Many populations of organisms deplete their resources, causing population growth rates to decline as population densities increase. For the histerid beetle, Carcinops pumilio (Erichson), increase in density had a damping effect on female fecundity and was inversely proportional to body size and mass of first and second instar larvae. Developmental time was inversely proportional to body size and mass of first and second instar larvae reared at densities of 5, 10, 15, 20, 30, 40 and 50 pairs of males and females. Survival of second instar larvae decreased with increase in density but increased with increase in body size. The rate of oviposition was directly proportional to body size and mass of the adult females. The results show that density will be a critical factor in any mass-rearing programme for this predator of fly larvae.
A contribution on the South African millipede genus, Nematozonium Verhoeff, 1939 (Siphonophorida : Siphonorhinidae)Source: African Entomology 12, pp 217 –222 (2004)More Less
The siphonorhinid diplopod genus Nematozonium Verhoeff, 1939, the only African representative of the order Siphonophorida, occupies disjunct areas in KwaZulu-Natal and Mpumalanga provinces, South Africa, primarily in the Drakensberg Range; it may also occur in the detached part of Eastern Cape Province and the countries of Lesotho and Swaziland. The millipedes are pallid and thread-like, ≤ 0.5 mm wide, and exhibit the elbowed antennae that are diagnostic for the family; they closely resemble sympatric individuals of the polyzoniidan genus Burinia Attems, 1926, which have short, sublinear antennae. Two species have been described, N. filum Verhoeff, 1939, the type species, and N. elongatissimum Verhoeff, 1940, and the latter is provisionally placed in synonymy under the former based on the proximity of the type localities and segmentation variation in the available specimens. The gonopods of a male syntype of N. filum are illustrated for the first time. Beyond characterizing the species, the gonopod structure suggests that a divided ultimate podomere of the posterior gonopod into two or more terminal branches may be diagnostic for the Siphonorhinidae in addition to the subtriangular head and elbowed antennae.
The impact of an invasive ant, Linepithema humile (Mayr) (Hymenoptera : Formicidae), on the dispersal of the elaiosome-bearing seeds of six plant speciesSource: African Entomology 12, pp 223 –230 (2004)More Less
Linepithema humile has invaded pristine areas in the Western Cape Province, South Africa, displacing important myrmecochorous ant species. The impact of this invasion on the dispersal of six species of elaiosome-bearing seeds varying in size, shape and mass was investigated. Linepithema humile failed to disperse heavy elaiosome-bearing seeds, although it readily removed lighter seeds like those of Polygala myrtifolia. This suggests that areas dominated by small ant species like L. humile would be characterized by low dispersal rates for heavy seeds. Indigenous ants in areas uninvaded and invaded by L. humile did not respond equally well to six elaiosome-bearing seeds. More of the heavier Leucospermum cordifolium than the lighter Podalyria calyptrata and Paranomus reflexus seeds were removed by ants in uninvaded areas. In invaded areas the heavier P. myrtifolia seeds were dispersed more readily than the lighter Agathosma ovata seeds. There was no indication of any specificity in the seed-ant interaction because the introduced ant, L. humile, dispersed smaller seeds. In addition, P. calyptrata, which occurs naturally in the study area, was not taken preferentially to other species of seed by myrmecochorous ants.
The South African Meligethes of the M. amplicollis-complex (Coleoptera : Nitidulidae : Meligethinae)Source: African Entomology 12, pp 231 –242 (2004)More Less
The known South African species of the M. amplicollis-complex in the genus Meligethes Stephens, 1830, are listed and revised. A diagnosis of this species-complex is given, and five species, known to occur in the Western and Eastern Cape Provinces, and southern KwaZulu-Natal, are described or re-described and illustrated. A new sibling species, M. aspalathi sp. n. is described from the southeastern Western Cape Province. Meligethes chevrolati Reitter, 1872, previously erroneously considered a synonym of M. amplicollis Boheman, 1851, is resurrected to specific rank. Meligethes imbricatus Easton, 1953, erroneously attributed to Australia, where Meligethes species are absent, is considered to be a synonym of M. chevrolati Reitter, 1872. Bionomical and ecological data on the species covered, which all use flowers of Fabaceae of the genus Aspalathus as larval host-plants, are also included.
Three new species of Yelicones Cameron (Hymenoptera : Braconidae : Rogadinae) from Madagascar, with a revised key to Afrotropical speciesSource: African Entomology 12, pp 243 –252 (2004)More Less
The following three new species of Yelicones are described and illustrated from Madagascar: Y. fisheri, Y. spectabile and Y. variegatus. Yelicones nigromaculatus Quicke & Chishti is recorded from the island for the first time. This brings the number of species known from the Afrotropical Region to twelve. A revised key is provided to differentiate Y. fisheri, Y. spectabile and Y. variegatus from similar species.
Growth and development of Chilo partellus (Swinhoe) (Lepidoptera : Crambidae) on cultivated and indigenous graminaceous host plantsSource: African Entomology 12, pp 253 –258 (2004)More Less
Chilo partellus (Swinhoe) (Lepidoptera : Crambidae) is an economically important pest of graminaceous crops such as maize, sorghum and pearl millet. Although C. partellus infestations are common in graminaceous crops, this species prefers to lay eggs on certain indigenous grasses. Indigenous graminaceous hosts that are preferred for oviposition but that result in poor larval survival have been used as trap crops in habitat management systems for this pest. In this study the growth and development of C. partellus on different host plants was investigated. These hosts were maize (Zea mays), sorghum (Sorghum bicolor), sweet sorghum (Sorghum bicolor), pearl millet (Pennisetum glaucum) and the grasses, P. purpureum (Napier grass) and Hyparrhenia tamba (blue thatching grass). Head capsule width, larval and pupal numbers and weight and development period for larvae and pupae were recorded. While larval survival on crops was high, no larvae pupated on indigenous grasses. Eclosion was observed from the pupae collected from maize, sorghum, sweet sorghum and pearl millet but not from the grasses. This study determined that the indigenous grasses, H. tamba and P. purpureum are poor hosts for C. partellus compared to the cultivated crops and that they therefore have characteristics that qualify them as potential trap crops for this pest.
Discovery of calcium enrichment in cutting teeth of parasitic wasp ovipositors (Hymenoptera : Ichneumonoidea)Source: African Entomology 12, pp 259 –264 (2004)More Less
Energy dispersion X-ray spectrometry of the ovipositor tips of two species of parasitic wasps, Gabunia sp. (Ichneumonidae : Cryptinae) from Uganda and the cosmopolitan Heterospilus prosopidis (Braconidae : Doryctinae) show that they have high concentrations of calcium as well as of manganese associated with the apex of the lower ovipositor valve and in the former, specifically with the lower valve teeth. Previous studies had revealed only manganese in the ovipositors of ichneumonoids, and the discovery of highly calcium-enriched cutting teeth might indicate the involvement of biomineralization, in addition to transition metal-protein complexes, in cuticular hardening in these parasitic wasps. Comparisons with related taxa indicate that the calcium enrichment is not present in all members of their groups.
Tetramorium insolens Smith (Hymenoptera : Formicidae) : a new record for Mauritius, Indian Ocean : short communicationSource: African Entomology 12, pp 265 –267 (2004)More Less
Invasive ants are a major challenge to conservation (Sanders et al. 2003). The negative effects of invasive ants are most significant on oceanic islands (Jourdan 1997). The impact of invasive ants include declines of arthropods, with direct and indirect effects extending to all trophic levels (Holway et al. 2001).
A new genus of Permian Plecoptera (Afroperla) from KwaZulu-Natal, South Africa : short communicationSource: African Entomology 12, pp 268 –270 (2004)More Less
During the compilation of an inventory of Upper Permian Beaufort Group fossil insects (Van Dijk & Geertsema 1999) the Plecoptera (Perlaria, stoneflies) were overlooked. Apart from listing, there was at that time little to add as the known fossils, both those at the Natal Museum and those at the Bernard Price Institute, had received a thorough treatment in Riek (1976a).
Oxysychus genualis (Walker) (Hymenoptera : Pteromalidae) : first record of an indigenous parasitoid of the introduced eucalyptus borer, Phoracantha semipunctata (Coleoptera : Cerambycidae), in South Africa : short communicationAuthor G.L. PrinslooSource: African Entomology 12, pp 271 –274 (2004)More Less
There has been an ongoing interest in the hymenopterous parasitoids of the eucalyptus borer, Phoracantha semipunctata (Fabricius) (Cerambycidae), in South Africa since its accidental introduction from Australia almost one hundred years ago. Attempts at the biological control of this notorious eucalypt pest, and of the closely related P. recurva Newman, through the importation of parasitoids from Australia.
Author D.A. BarracloughSource: African Entomology 12, pp 275 –277 (2004)More Less
The Camillidae are a small family of drosophilidlike acalyptrate Diptera belonging to the superfamily Ephydroidea. Most recently published information suggests that the family is coprophagous and mostly associated with the droppings of small mammals, where the immature stages develop (Kirk-Spriggs et al. 2002).
Fitness traits and larval survival of the lappet moth, Streblote panda (Hübner, 1820) (Lepidoptera : Lasiocampidae), reared on different host plants : short communicationSource: African Entomology 12, pp 278 –282 (2004)More Less
Streblote panda (Hübner, 1820) is a moth species that lives in low and littoral areas of the Iberian Peninsula, and North Africa from Egypt to the Atlantic coast of Morocco. Their caterpillars are highly polyphagous, feeding on leaves of different evergreen plants from a broad spectrum of plant families (Freina & Witt 1987).
Assessment of Chaussieria capensis (Acari : Anystidae) as a predator of Halotydeus destructor (Acari : Penthaleidae) : short communicationSource: African Entomology 12, pp 286 –290 (2004)More Less
The red-legged earth mite or black sand mite Halotydeus destructor (Tucker) (Acari: Penthaleidae) (RLEM) is a very damaging pest of crops and pastures in southern Australia. Its native range is the western and southwestern areas of South Africa, and from there it was accidentally introduced into Australia.