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- Journal of the Entomological Society of Southern Africa
- OA African Journal Archive
- Volume 45, Issue 1, 1982
Journal of the Entomological Society of Southern Africa - Volume 45, Issue 1, 1982
Volumes & issues
Volume 45, Issue 1, 1982
The toxicity of methidathion and citrus spray oil to mature and immature stages of OP-resistant and susceptible red scale, Aonidiella aurantii (Mask.) (Hemiptera: Diaspididae)Source: Journal of the Entomological Society of Southern Africa 45, pp 01 –13 (1982)More Less
The toxicity of methidathion and narrow range citrus spray oil to three stages of red scale of two different field strains was investigated. Scales of the Letsitele strain were found to be highly resistant to methidathion compared with those of the Karino strain, and each stage was more resistant than the one preceding it, the resistance factor ranging from 75 for the first stage to 183 for the unfertilized adult female. Unfertilized females of the same strain were about six times more susceptible to methidathion alone when they were on leaves than when they were on fruits of lemon. The susceptibility of three developmental stages to spray oil did not differ. The addition of 1% spray oil to methidathion increased the toxicity to Letsitele scales by about 40 times. Fertilized females surviving treatment with 1,6% oil produced live crawlers (most of which later died as a result of the long residual effect of oil in the laboratory) but those surviving treatment with a mixture of methidathion plus oil did not; all the crawlers died under the scale of the female. Since unfertilized females are more susceptible to insecticides than fertilized females, sprays in orchards will be more effective if they are applied when the former are at their peak. This period can readily be determined by monitoring the males, which are present simultaneously.
Source: Journal of the Entomological Society of Southern Africa 45, pp 15 –20 (1982)More Less
The secretion or the scent gland or adults and nymphs or Carlisis wahlbergi was analysed by gas chromatography, and the compenents were identified by mass spectrometry. No difference was observed between the secretions or males and females and between those or nymphs and adults. The relative amounts of the components did not differ significantly in samples analysed during a nine-month period. The major components were acetic acid (66%), trans-2-hexenal (17%) and 3-hydroxybutanal (14%). A minor component was 2-hexanol (I %). Traces or carbon dioxide, carbon monoxide, water and even naphthalene were detected in some samples. The presence and functions or all the components are briefly discussed.
Discovery of cotypes of Poecilmitis felthami felthami (Trimen) (Lepidoptera: Lycaenidae) in the Feltham collectionAuthor Martin VilletSource: Journal of the Entomological Society of Southern Africa 45 (1982)More Less
A series of eighteen specimens of Poecilmitis felthami (Trimen) has been discovered in the H. L. L. Feltham epidoptera collection, housed in the Zoology Department at the University of the Witwatersrand. The series is designated 'Z. Felthami Trimen/with type specimens/Retreat-Cape Flats'. In the series is a male designated Type of/Zritis/Felthami /Trimen' and 'Trans. Ent./Soc. Lond./1904'. Its data label reads: '10.11.'oo/Retreat/Flats'.
Author J.G. TheronSource: Journal of the Entomological Society of Southern Africa 45, pp 23 –26 (1982)More Less
Author G. ViggianiSource: Journal of the Entomological Society of Southern Africa 45, pp 27 –32 (1982)More Less
Three new species of Aphelinids are descriptionbed from Africa. They are Encarsia mineoi, a parasite of Bemisia tabaci (Genn.) in Lybia, E. abate; and Eretmocerus cadabae, parasites of Aleuroplatus cadabae Priesner & Hosni in Ethiopia. Ablerus pumilus Annecke & Insley is recorded from Ethiopia on Aleuroplatus cadabae for the first time.
Isazophos, a promising new insecticide for control of larvae of fossorial rhizophagous beetles (Coleoptera: Scarabaeoidea) in pineapple fieldsAuthor G.J. PettySource: Journal of the Entomological Society of Southern Africa 45, pp 33 –41 (1982)More Less
The value of isazophos (O-(5-chloro- I -methylethyl- IH- I,2, 4, -triazol-3-y!l) O, O-diethyl phosphorothioate) as a preplant soil insecticide and nematicide in pineapple production was assessed at dosages of 2,5 to 15,0 kg/ha, It was concluded that 10 kg/ha is the optimum dosage of both biological efficacy and economics arc considered. Even at 5kg/ha, the residual efficacy against larvae of the beetle Adoretus tessulatus Burm, exceeded that of the current standards, HHDN and dieldrin, for more than 48 weeks according to laboratory bioassays. In field trials in which fruit yield, root mass, nematode root-galling and ratoon sucker development were measured, outstanding results were obtained with isazophos at 10 kg/ha: e.g. plant- and ratoon-crop yields were respectively double and more than quadruple that or the untreated control There were no detectable residues in fruit at time of harvest even after a dosage of 15 kg/ha. Evidence was obtained that isazophos has a high potential as a postplant topical soil treatment for elimination of rhizophagous beetle larvae.
Author J.R. WilliamsSource: Journal of the Entomological Society of Southern Africa 45, pp 43 –56 (1982)More Less
Six species of Issidae from the Mascarenes are descriptionbed. Two of these are new, namely Tylana nigromaculata spec. nov. from Mauritius and Reunion, and T. rodriguensis spec. nov. from Rodrigues. T. cristata (F.), T. carinata (F.), T. indecora Stal and T. mameti Synave are redescriptionbed. A lectotype is designated for T. indecora. T. similis Synave is sunk as a synonym of T. carinata, while T. macabeana Synave and T. conspersa Synave (nec Schmidt) are considered synonyms of T. indecora.
Species richness and relative abundance of female mosquitoes at a site in the western Orange Free StateSource: Journal of the Entomological Society of Southern Africa 45, pp 57 –67 (1982)More Less
Mosquitoes were caught at weekly intervals for three years from 1976 to 1978 in four light-traps placed near a group of typical mosquito breeding sites on the farm Danielskuil in the arid western Orange Free State: 25 species were found to be present, of which 8 had not previously been recorded from the Orange Free State. The numbers of females of each species caught in the three seasons into which every year was divided are given in tables. The three commonest species were, in descending order of abundance, Culex theileri, itedes juppi and the Ae. durbanensis group. They account for 84,7% of the total catch of 143 483 females, most of which (128 030) were caught in 1976. Only Cx. theileri was at all common during the winter months (943 females in three years); other species occasionally caught in winter included Cx. univillatus (40 females) Ae. juppi (30), and Culiseta longiareolata (26).
Temporal fluctuations in the numbers of female mosquitoes trapped at a site in the western Orange Free StateSource: Journal of the Entomological Society of Southern Africa 45, pp 69 –92 (1982)More Less
The abundance and temporal distribution patterns of the females of the seven most abundant mosquito species trapped at weekly intervals over a period of three years were analysed in detail. Mean weekly catches and mean weekly climatic or climate-associated variables were used in all the analyses. The observed catch distributions were compared with moving average and unconditional circular distributions fitted to the same data. This approach identified the periods during which each species can be expected to occur and gave an indication of their relative numbers. The influence of individual variables or combinations of variables on the distribution and abundance was identified by model selection. The distribution of each species as calculated under its most successful model was compared with its observed distribution. In general there was good agreement between observed and calculated distributions. The limitations and value of the approach are discussed.
Author P.R. AtkinsonSource: Journal of the Entomological Society of Southern Africa 45, pp 93 –104 (1982)More Less
Male moths of Eldana saccharina Walker, in common with other gallerines, have a gland at the base of each fore wing. The gland has two parts; a main part consisting of large oval cells and a duct opening to the exterior via an orifice facing towards the wing tip, and a secondary part of which the duct does not open to the outside. Males also have prominent hair-pencils on the eighth abdominal segment. The hairs, which are inserted into large hooked secretory cells, are extruded past the outer surface of the claspers. These are themselves studded with large secretory cells, modified from trichogen celis. In the female, there is a small apparently secretory region of columnar cells with cylindrical hairs at the posterior edge of the seventh abdominal segment.
The taxon Parvidens (Diptera: Psychodidae: Phlebotominae) with description of a new species from NamibiaAuthor Ian H. DavidsonSource: Journal of the Entomological Society of Southern Africa 45, pp 105 –108 (1982)More Less
Author Rami Van Hamburg H. and KfirSource: Journal of the Entomological Society of Southern Africa 45, pp 109 –121 (1982)More Less
Replicated field plots of cotton at Groblersdal and Rust der Winter were treated as follows during the 1980-81 growing srason and the yields were measured: (A) sprayed weekely. (B) never sprayed (T1), (T2), (T4), (T6) sprayed when one or more. two or more. four or more. or six or more bollworm larvae were found in weekly examinations of 12 plants per plot. All sprays were of cypermethrin at 35 g/ha. The predominant bollworm species was Heliothis armiger (Hubner): Diparopsis castanea Hampson and Earias spp. (prohably E. insulana (Boisduval) and E. biplaga Walkeri were also present. Yields were depressed in the plots sprayed weekly, probably because of phytotoxicity. The lowest yields were obtained from unsprayed plots and the highest from T1 plots (sprayed 5 times at both sites). The sucressin test thresholds T1 toT6 were associated with a large (41 % overall) and significant decrease in yield at Groblersdal but not at Rust der Winter, where the difference was small (15% overall) and could have been due to chance. Some reasons for this contrast are suggested. Yields were well correlated with mean larval numbers for the season. The relevance of these findings to the establishment of economic thresholds based on larval counts is discussed.