African Entomology - Volume 14, Issue 2, 2006
Volumes & issues
Volume 14, Issue 2, 2006
Origin of a Mediterranean fruit fly, Ceratitis capitata (Wiedemann), outbreak determined by DNA analysisSource: African Entomology 14, pp 205 –209 (2006)More Less
Sterile male Mediterranean fruit flies, Ceratitis capitata (Wiedemann), have been released in the Hex River Valley since 1999 in a sterile insect technique (SIT) programme to suppress this pest on export table grapes. The source of these sterile fruit flies was the Mediterranean fruit fly rearing facility in Stellenbosch, where a genetic sexing strain of C. capitata made it possible to release only male fruit flies in the SIT field operation. In December 2001 an outbreak of fruit flies in export table grapes in the Hex River Valley was reported. Growers in the Hex River Valley ascribed this infestation to the presence of unsterilized C. capitata females in deliveries of sterile C. capitata males from the rearing facility, and blamed the facility for the resulting crop losses. Fruit fly specimens collected from grapes in the infestation area were subjected to mitochondrial DNA analysis to compare the distribution of haplotypes of the infesting flies from the SIT area with that of the laboratory strain. None of the analysed flies showed the genetic fingerprints present in the genetic sexing strain in the rearing facility. This demonstrated that the origin of the infestation was not the rearing facility, but most probably arose from infestations of wild C. capitata in uncontrolled commercial, domestic and wild fruit fly host plants in the SIT area.
Oviposition preference and survival of the maize stem borer, Busseola fusca (Lepidoptera : Noctuidae), on Napier grasses, Pennisetum spp., and maizeSource: African Entomology 14, pp 211 –218 (2006)More Less
Napier grass, Pennisetum purpureum, is used successfully as a trap crop for lepidopterous stem borers in Africa. This paper reports on the evaluation of the suitability of Napier grass varieties as trap crops for Busseola fusca (Lepidoptera: Noctuidae). This was done through oviposition preference tests and evaluation of larval survival on different varieties. Napier grass varieties were collected from the wild, from research institutions and farmers growing them as forage crops. In multiple-choice tests with the different Napier grass varieties, differences in oviposition preference were observed. Results from two-choice tests with Napier grass and maize plants indicated B. fusca moths have no marked difference in oviposition preference. However, compared to maize, larval survival on Napier grasses was low and a rapid decline in larval numbers was observed over the first week after inoculation on the grasses. A scanning electron microscope study of trichomes on Napier grass and maize leaves was conducted and the relationship between trichome number and larval survival determined. Significant negative correlations (P < 0.03) were observed between trichome numbers and larval survival.
The bionomics of the egg parasitoid Telenomus busseolae (Gahan) (Hymenoptera : Scelionidae) on Busseola fusca Fuller and Sesamia calamistis Hampson (Lepidoptera : Noctuidae) in KenyaSource: African Entomology 14, pp 219 –224 (2006)More Less
The suitability of 1-3-day-old eggs of Busseola fusca Fuller and Sesamia calamistis Hampson (Lepidoptera: Noctuidae) to a strain of Telenomus busseolae (Gahan) (Hymenoptera: Scelionidae) collected in mid-altitudes of Kenya was assessed in the laboratory. For both species, age of egg did not affect progeny production but two-day-old B. fusca eggs yielded more progeny than S. calamistis eggs of the same age. With S. calamistis, development time of T. busseolae increased with age of eggs, while host species had no effect. Neither borer species nor age of eggs significantly affected the sex ratio. Longevity of T. busseolae was greater and total fecundity higher on B. fusca than S. calamistis. The intrinsic rate of increase and the net reproductive rate were greater with B. fusca than S. calamistis eggs as host. The values were considerably lower than those reported from the same species in West Africa, indicating that there are differences in strains between regions. Females begun ovipositing on the first day of emergence and the average daily number of eggs laid and the proportion of females decreased with age of the female, on both hosts. The ability of T. busseolae females to accept and develop in B. fusca and S. calamistis of different ages is an advantage, especially during times of host scarcity, which is common during the dry-season. In a Y- tube experiment no preference for either stemborer species was observed. Similarly, in the field, there was no significant variation in parasitism between B. fusca and S. calamistis eggs.
Author W. WesolowskaSource: African Entomology 14, pp 225 –256 (2006)More Less
Nineteen species of jumping spiders of the family Salticidae are represented in material from the Brandberg survey in Namibia. Only two species have previously been recorded from Namibia. Eleven new species are described: Aelurillus mirabilis, Evarcha acuta, Habrocestum namibicum, Heliophanus montanus, Langona pilosa, L. vitiosa, Mashonarus brandbergensis, Pellenes tharinae, Phlegra karoo, Ph. Tenella and Pseudicius adustus. Menemerus insolidus Wesolowska, 1999, is transferred to the genus Icius and a new combination Icius insolidus is proposed; the first description of the male of the species is also given.
Arthropod communities in Proteaceae infructescences : seasonal variation and the influence of infructescence phenologySource: African Entomology 14, pp 257 –265 (2006)More Less
Arthropods associated with infructescences of nine Proteaceae species were collected on a monthly basis over a two-year period. A total of 66 morphospecies, over 7000 individuals, belonging to 45 arthropod families, were collected. Plant species with larger infructescences showed the highest arthropod species richness and abundance. Protea laurifolia, P. repens, P. nitida, P. burchellii and P. neriifolia harboured very similar arthropod assemblages. Seasonal patterns were also observed in the arthropods associated with Protea spp. infructescences, with abundance and richness levels peaking during the wetter autumn and winter months. There is an increase in arthropod species richness and abundance as the infructescences of the Protea spp. age. Results of this study elucidate patterns of association between a range of Proteaceae and the arthropods contained within their infructescences.
Effects of crop sanitation on banana weevil, Cosmopolites sordidus (Germar) (Coleoptera : Curculionidae), populations and crop damage in UgandaSource: African Entomology 14, pp 267 –275 (2006)More Less
Crop sanitation, i.e. destruction of crop residues, has been hypothesized to lower banana weevil damage by removing adult refuges and breeding sites. Although it has been widely recommended to farmers, limited data are available to demonstrate the efficacy of this method. The effects of crop sanitation on banana weevil populations and damage were studied in an on-station trial in Uganda. Treatments included low, moderate and high levels of sanitation. Banana weevil populations, estimated by trapping and mark and recapture methods, were lowest in the high sanitation treatment. However, banana weevil damage was either not significantly different among treatments or lower in low sanitation treatments. Similarly, increases in crop sanitation level were not reflected in higher yields. The data from this trial suggest that crop sanitation is not an effective means of managing banana weevil and contrasts with results from an on-farm study in which sanitation reduced both weevil numbers and damage. Possible factors explaining the different outcomes of the two studies are discussed.
Screening of South African sugarcane cultivars for resistance to the stalk borer, Eldana saccharina Walker (Lepidoptera : Pyralidae)Author M.G. KeepingSource: African Entomology 14, pp 277 –288 (2006)More Less
Resistant sugarcane cultivars are an important control measure for the stalk borer, Eldana saccharina Walker, in South African sugarcane, Saccharum spp. hybrids. Selection for resistance is based on field assessments and potted sugarcane screening trials of test cultivars. This paper describes the screening methodology and examines its efficacy for evaluating susceptibility to E. saccharina. Aims were to improve discrimination of borer susceptibility and to develop a quantitative, statistically meaningful method of rating cultivars. Test cultivars were planted in a replicated lattice design and artificially infested with E. saccharina. Four variables, namely length of stalk bored, number of internodes bored, numbers of surviving larvae+pupae, mass of larvae+pupae, that quantified borer damage and performance, were used to calculate a susceptibility/resistance rating for all cultivars on a 'one to nine' unit scale, where two units was equivalent to a 95 % confidence interval and the mid-point of the scale represented the control mean. Ratings were standardized and independent of those of other test cultivars within the same trial. Differences in susceptibility were significant in all trials and well discriminated in the majority. Improved discrimination produced a greater spread of cultivar ratings across the rating scale, facilitating the identification of resistant cultivars. The screening method and variables measured take into account the known resistant mechanisms to E. saccharina and provide a means of estimating the likely impact of cultivars on area-wide pest management in terms of larval survival and moth production.
Source: African Entomology 14, pp 289 –292 (2006)More Less
The workers of the thermophilic ant, Ocymyrmex laticeps, have large pygidial glands, the contents of which are dominated by indole-3-ethanol, a newly discovered substance in insect secretions. The Dufour glands of workers contain a mixture of saturated, unsaturated and methyl-branched hydrocarbons and small amounts of fatty esters.
Source: African Entomology 14, pp 293 –305 (2006)More Less
Six species of Melitta Kirby are recorded from southern Africa and one from East Africa. Four names are placed into synonymy : Melitta capensis, Melitta longicornis and Melitta turneri are junior synonyms of Melitta arrogans, and Melitta flavipes is a junior synonym of Melitta schultzei. Three new species have been described from southern Africa: Melitta whiteheadi Eardley sp. n., Melitta danae Eardley sp. n. and Melitta barbarae Eardley sp. n., and one from East Africa, namely Melitta katherinae Eardley sp. n. Melitta rufipes Friese is transferred to Rediviva.
Use of pheromone traps to assess Lasioderma serricorne (F.) (Coleoptera : Anobiidae) infestation in a cigarette factory on the Cape Verde islandsSource: African Entomology 14, pp 307 –315 (2006)More Less
Lasioderma serricorne (F.) (Coleoptera: Anobiidae) is the most serious insect threat to stored tobacco and cigarettes on the Cape Verde islands. A monitoring programme using sex pheromone traps for the cigarette beetle was initiated to detect sources of infestation and to assess the risk of tobacco damage. Trials were conducted to obtain estimates of the mean density of L. serricorne and to analyse its spatial pattern. The manager of the cigarette factory used the trap records to assess risk and implemented an empirical action threshold of 10 insects/week/trap. Post-fumigation data collection showed that the pest populations had been reduced by 87 %. The variability in the trap catches indicated an aggregated pattern of distribution and negative binomial distribution fitted the data more accurately than the Poisson distribution. From Iwao's Patchiness or Mean Crowding Regression, at high relative population densities, it was shown that the individuals may form colonies. Although the spatial pattern of the adult male cigarette beetles followed an aggregated distribution at high relative densities, when these relative densities were lower the spatial pattern changed and random and uniform populations occurred.
Author Jason G.H. LondtSource: African Entomology 14, pp 317 –328 (2006)More Less
Two thousand afrotropical asilid prey records, databased by the Natal Museum, are analysed. The key orders of arthropods preyed upon are, in order of importance, Hymenoptera, Diptera, Coleoptera, Orthoptera, Hemiptera, and Lepidoptera, that together accounted for 96%of records. Insect families with sufficient data to warrant special mention are: Coleoptera (Scarabaeidae), Diptera (Asilidae, Bombyliidae, Calliphoridae, Muscidae, Tabanidae, Tipulidae, Syrphidae, Tachinidae, Empidae), Hemiptera (Cicadidae, Cicadellidae, Lygaeidae, Pentatomidae, Cercopidae), Hymenoptera (Formicidae, Apidae, Halticidae, Megachilidae), Orthoptera (Acrididae). Asilid genera with sufficient data to warrant special attention, are: Apocleinae (Alcimus, Dasophrys, Neolophonotus, Philodicus, Promachus), Dasypogoninae (Pegesimallus), Laphriinae (Lamyra, Nusa, Stiphrolamyra), Laphystiinae (Hoplistomerus, Trichardis), Leptogastrinae (Euscelidia, Lasiocnemus), Stenopogoninae (Acnephalum, Daspletis, Gonioscelis, Microstylum, Rhabdogaster, Scylaticus), Trigonomiminae (Damalis). A number of genera appear to be specialist feeders - Scylaticus on Hemiptera, Lasiocnemus on Araneida, Hoplistomerus on Scarabaeidae and Bana on Apis mellifera. Female asilids generally outnumber males 1.5 to 1 in records of prey capture, but the extent of this imbalance varies from one subfamily to another.
The biology of Amphicallia pactolicus (Butler) (Lepidoptera : Arctiidae), a defoliator of Crotalaria speciesSource: African Entomology 14, pp 329 –336 (2006)More Less
Crotalaria grahamiana (Wight & Arn.) (Leguminosae) is an exotic shrub widely used as a short-rotation cover crop or planted fallow in eastern and southern Africa. Recently, Amphicallia pactolicus (Butler) (Lepidoptera: Arctiidae), an indigenous insect, has become a major defoliator of the shrub in eastern and southern Africa. We studied the feeding habits of A. pactolicus and evaluated the suitability of different species of Crotalaria for its development. The life cycle of A. pactolicus is described for the first time. The larval stage of A. pactolicus passed through six instars. Larvae that fed on flowers and pods, gained body mass faster and had shorter larval duration compared to those that fed on leaves. Out of the eight Crotalaria species tested (C. agatiflora Schweinf., C. grahamiana Wight & Arn., C. laburnifolia L., C. ochroleuca G. Don., C. paulina Schrank, C. pycnostachya Benth., C. striata DC. Benth and C. incana L.), only C. incana was rejected by the larvae. A significant proportion of the food ingested was recycled back to the soil in the form of droppings. The nitrogen, phosphorus and potassium concentrations of the faeces were similar to those of the plant material ingested. Reproductive tissues of the plant are most affected, thus indicating greater risk for seed multiplication and less danger to short-duration (6-8 months) fallow planted for soil fertility benefits. Early infestation allows more generations of A. pactolicus to develop and has the potential to cause a significant biomass yield loss.
Modelling the spatial patterns and interspecific interactions between three chrysomelid beetles defoliating the multipurpose agroforestry tree Sesbania sesban in AfricaSource: African Entomology 14, pp 337 –348 (2006)More Less
The population dynamics of single species can be understood only in the context of interactions within an ecological community. In this study we used theoretical and empirical models to describe the spatial pattern of the Afrotropical leaf beetles Mesoplatys ochroptera Stål, Exosoma and Ootheca spp. defoliating the agroforestry tree (Sesbania sesban (L.) Merril). We used the Poisson, negative binomial distribution (NBD), Taylor's power law and Iwao's mean crowding models to determine (1) intraspecific spatial patterns and conspecific interactions within a population, (2) interspecific interaction between their populations, and (3) derive a common sampling plan for the three species. The spatial patterns of larvae and adult M. ochroptera were adequately described by the negative binomial, while those of Exosoma and Ootheca fitted the Poisson distribution. Taylor's power law gave very good fit (r2 >0.80) except for Ootheca in Zambia, while Iwao's mean crowding gave poor fit to the spatial pattern of M. ochroptera larvae and Ootheca. The slopes of the variance-mean relationships were significantly greater than unity for adults and larvae of M. ochroptera, indicating aggregated distribution, while those for Exosoma and Ootheca were closer to unity, indicating spatial randomness. The three species showed random association with varying degrees of niche overlap. Therefore, the null hypothesis of spatial independence between the populations of M. ochroptera and Exosoma, and adult M. ochroptera and Ootheca was rejected. Hence, a common sampling plan was developed for estimation of the population densities of the three species at the same time.
Source: African Entomology 14, pp 349 –355 (2006)More Less
The predominant predatory arthropods breeding in manure at two census sites in the Western Cape Province, South Africa, were found to be Carcinops pumilio (Erichson) (Coleoptera: Histeridae), Macrocheles muscaedomesticae (Scopoli) (Acarina: Macrochelidae), and Philonthus sordidus (Gravenhorst) (Coleoptera: Staphylinidae). This was similar to other localities in the world. At both sites, adults of C. pumilio appeared within a week of manure cleanout and subsequently increased in numbers. The majority of C. pumilio, P. sordidus and M. muscaedomesticae showed preference for a narrow range of manure moisture (70-75 %). Very few predators occurred at moisture levels above 80 %. The three species showed a wide range of temperature tolerance (12-31 °C). Carcinops pumilio preferred aged manure, and M. muscaedomesticae and P. sordidus fresh manure. Thus they could be used to complement one another in IPM augmentation strategies.
Larval development of the carrion-breeding flesh fly, Sarcophaga (Liosarcophaga) tibialis Macquart (Diptera : Sarcophagidae), at constant temperaturesSource: African Entomology 14, pp 357 –366 (2006)More Less
Larvae of Sarcophaga (Liosarcophaga) tibialis Macquart were raised on chicken liver under six different constant temperatures. Maximum survival indicated an optimal developmental temperature of near 20 °C, while trends in mortality, larval length and larval mass implied that the thermal window for successful development lay between 15 °C and 30 °C. Using a recently described method to estimate a simple thermal summation model, it was found that the timing of the end of the feeding phase could be estimated by a developmental zero (D0) of 5.2 °C (S.E.=1.21) and a thermal summation constant (K) of 106.4 d°C (S.E.=8.31) and of the end of the wandering phase by D0 = 4.1 °C (S.E. = 0.39) and K = 126.7 d°C (S.E. = 3.28). Published development times at constant temperatures were compiled for 19 other species of flesh flies, and the developmental constants were calculated for six species for which sufficient data were accumulated.
Recruitment behaviour in the ponerine ant, Plectroctena mandibularis F. Smith (Hymenoptera : Formicidae)Source: African Entomology 14, pp 367 –372 (2006)More Less
Although workers of Plectroctena mandibularis laid trails with their stings while foraging, the trails appeared to be for individual orientation, because they never recruited nestmates to prey. However, both workers and queens laid trails when recruiting nestmates of either caste to new nest sites. During trail-laying, fluted hairs on the posterior edge of tergite VI were dragged along the ground, presumably applying a pheromone to the substrate. Anatomical and behavioural evidence suggests that pygidial gland secretions moved from the intersegmental pygidial gland between tergites VI and VII into a fingerprint-like, lamellar cuticular reservoir on the pygidium, and from there via the hairs to the substrate. These results suggest that recruitment may be crucial to moving nests but of value only to certain types of foraging, and that recruitment might even have originated in the Formicidae in the context of colony relocation, and then secondarily evolved to assist foraging.
Potential of neem, Azadirachta indica A. Juss., in the management of Chilo partellus (Swinhoe) on maize in KenyaSource: African Entomology 14, pp 373 –379 (2006)More Less
The efficacy of neem (dirachta indica A. Juss.) seed powder and aqueous extract against spotted stem borer, Chilo partellus (Swinhoe), on maize (Zea mays) cultivars was investigated in western Kenya. Hybrid 511 and ICZ3 maize plants were infested with blackhead stage egg batches of C. partellus three weeks after crop emergence. Neem seed powder, neem seed powder-sawdust mixture and a 10 % aqueous neem seed extract were applied four weeks after crop emergence. Dipterex was used as a check treatment and plots with untreated plants were included as controls. Foliar application of neem seed products and chemical insecticide considerably suppressed the densities of C. partellus, markedly reduced leaf damage and stem-tunnelling, and improved yield in both cultivars. Application of about 3 g plant/neem seed powder and 500 l/ha of 10 % aqueous neem seed extract applied four weeks after crop emergence provide adequate protection against damage by C. partellus comparable to conventional insecticide and avert consequent yield loss.
Longevity and survival of colonies of Messor capensis (Formicidae : Myrmicinae) in the Karoo, South Africa : short communicationAuthor W.R.J. DeanSource: African Entomology 14, pp 381 –383 (2006)More Less
Ants play an important role in recycling nutrients in arid and semi-arid ecosystems (Whitford 1986, 2002; Wilby et al. 2001), including the semi-arid Karoo, South Africa (Dean & Yeaton 1993a). In the Karoo, granivorous harvester ants, Messor capensis, are central-place foragers, bringing seeds to nests from up to 20 m (Dean 1991).