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Volume 61 - Issue 4 - June 1972

Contents

Review Articles

  • Insect chemosterilants: a review

  • D. G. Campion
  • Published online by Cambridge University Press:
    10 July 2009, pp. 577-635

  • In this paper the present status of insect chemosterilants is reviewed. Chemosterilants may be categorised into eight main chemical groups. Practical control measures involving the use of chemosterilants are discussed, also the persistence of these substances when applied to the insect. The gross effects of chemosterilants on insect reproductive systems and also the effects on egg develpment when female insects are mated to chemosterilised males are described, including dominant lethality, reciprocal translocation, enzyme inhibition and sperm inactivation. The possibilities of recovery of fertility and insect resistance to the sterilising effects of chemosterilants are discussed. Endocrine misfunction and chemosterilant action are related. The only practical chemosterilants as control agents are the aziridines although mutagenic hazards associated with these substances preclude their widespread usage. The sterilising activity of certain insect hormone analogues and related substances encourages the belief that safe insect specific sterilising agents can be found.

  • A review of estimates of numbers in some types of desert locust (Schistocerca gregaria (Forsk.)) populations

  • L. V. Bennett, P. M. Symmons
  • Published online by Cambridge University Press:
    10 July 2009, pp. 637-649

  • A review is given of estimates, both published and unpublished, of numbers in some types of desert locust (Schistocerca gregaria (Forsk.)) populations, and suggestions are made for further work in this field. For swarming adult populations, estimates of volume and area density and of the relative sizes of settled and flying swarms have been reviewed. For gregarious nymphal (hopper) populations, the area density of late-instar bands and the infestation rate following gregarious breeding have been examined. There is insufficient evidence to give estimates of the average numbers in any of these types of population with confidence, or to be able to estimate the environmental and physiological factors with which variation in density is correlated. It is not possible to make generally valid estimates of the densities of non-gregariously behaving populations. Practically no research has been done on population estimation methods suitable for such populations, although, in practice, estimates are made during field surveys. The principles underlying valid sampling techniques, and valid selection of the sample in various situations, are described.

Original Articles

  • On the origin of the wet-season form of Zonocerus variegatus (L.) (Orth., Acrididae) in southern Nigeria, with some biological notes

  • T. Ajibola Taylor
  • Published online by Cambridge University Press:
    10 July 2009, pp. 661-667

  • Previous reports and field observations at Ibadan and in northern Nigeria have established the occurrence of a dry-season form and a wet-season form of Zonocerus variegatus (L.). The wet-season form in the savanna areas of northern Nigeria is shown to be virtually identical with that from southern Nigeria on the basis of breeding seasons, habitat and morphometrics. Morphometrics show the wet- and dry-season forms to be distinct. It is suggested that the dry-season form in the wet rain forest zone spread into the dry savanna areas giving rise to a wet-season form adapted to the different climatic conditions. The increasing occurrence of the wetseason form in the south probably represents a re-invasion by the northern wetseason form.

  • Extracellular ducts within the wall of the spermatheca of tsetse flies (Glossina spp.) (Dipt., Glossrnidae)

  • A. M. Jordan
  • Published online by Cambridge University Press:
    10 July 2009, pp. 669-672

  • Each spherical spermatheca of Glossina austeni Newst. is composed of a cuticular lining of the lumen which is surrounded by a layer of secretory cells. When the spermatheca is immersed in Amann's lactophenol the cells of the cellular layer lift away from the cuticular intima revealing numerous clubbed processes projecting outwards from the surface of the intima. Sections of spermathecae examined by transmission electron microscopy show that one clubbed process is associated with each cell of the cellular layer. The “porous” head of the process is within a fluidfilled cavity in the cell, lined with microvilli. The stalk of each process is an extracellular duct down which secretions from the cellular layer pass into the lumen of the spermatheca. It is considered that these secretions are the medium, probably containing nutrients, in which spermatozoa are held while in the spermatheca.

  • On the biology of Lioadalia flavomaculara (Deg.) (Col., Coccineffidae), a predator of the wheat aphid (Schizaphis graminum (Rond.)) in South Africa

  • H. Dick Brown
  • Published online by Cambridge University Press:
    10 July 2009, pp. 673-679

  • An account is given of the biology and different life stages of Lioadalia flavomaculata (Deg.), an important predator of the wheat aphid, Schizaphis graminum (Rond.), in the Orange Free State, South Africa. Eggs are laid in batches of 6–23 eggs, generally on the soil, and incubation takes 2.1–2.8 days at 32°C and 8.6–9.1 days at 16°C. There are four larval instars, the last of which has the longest duration; total development of the immature stages averaged 11.5, 161, 220, 30.2, 35.5 and 54.0 days at 32, 27, 24, 21, 18.5 and 16°C, respectively. Beetles mate within a few days of emergence and oviposition commences 3–10 days later, depending on temperature. Maximum fecundity averaged 858.5 eggs at 24°C. From 20.7 to 24.6 eggs per day were laid at the higher range of temperatures studied (24–32°C). Oviposition took place mainly during the day. Adult life span was 24–74.3 days.

Index of Authors

Index of Genera and Species

Front matter

  • BER volume 61 issue 4 Front matter

  • Published online by Cambridge University Press:
    10 July 2009, pp. f1-f6
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