Lake outlet blackflies ‐ the dynamics of filter feeders at very high population densities

Lake outlet blackflies ‐ the dynamics of filter feeders at very high population densities Larvae of the blackfly Simulium noelleri aggregated at very high population densities (up to 1.2 × 106 individuals m−2) at a lake outlet in Kent, United Kingdom. During 1983 and 1984 their first appearance in these large numbers was in late‐June and they completed three summer generations before the overwintering larval generation appeared in October. It is not known where the larvae overwinter but they recolonized the concrete steps of this outlet in May, together with larvae of the S. ornatum group which, however, were not found after completing one generation at this location. Female flies from the overwintering generation oviposited en masse during late‐June and the result was a well‐synchronized growth of larvae in the first summer generation. Within this, and other generations, there was A wide range of emergence times for adults; they could emerge early and were then relatively small, or could emerge later and were then relatively large. Females were always larger than males and the emergence of flies was protandrous. A very similar pattern of growth and emergence times was found at a site in Finland. In all generations, sex ratio was biased to males and the sex ratio in each generation was inversely correlated with population density. This ensured that there were sufficient males emerging, and surviving adult mortality, to guarantee fertilisation of the females which were more expensive to produce. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecography Wiley

Lake outlet blackflies ‐ the dynamics of filter feeders at very high population densities

Ecography, Volume 10 (1) – Mar 1, 1987

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Publisher
Wiley
Copyright
Copyright © 1987 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0906-7590
eISSN
1600-0587
DOI
10.1111/j.1600-0587.1987.tb00740.x
Publisher site
See Article on Publisher Site

Abstract

Larvae of the blackfly Simulium noelleri aggregated at very high population densities (up to 1.2 × 106 individuals m−2) at a lake outlet in Kent, United Kingdom. During 1983 and 1984 their first appearance in these large numbers was in late‐June and they completed three summer generations before the overwintering larval generation appeared in October. It is not known where the larvae overwinter but they recolonized the concrete steps of this outlet in May, together with larvae of the S. ornatum group which, however, were not found after completing one generation at this location. Female flies from the overwintering generation oviposited en masse during late‐June and the result was a well‐synchronized growth of larvae in the first summer generation. Within this, and other generations, there was A wide range of emergence times for adults; they could emerge early and were then relatively small, or could emerge later and were then relatively large. Females were always larger than males and the emergence of flies was protandrous. A very similar pattern of growth and emergence times was found at a site in Finland. In all generations, sex ratio was biased to males and the sex ratio in each generation was inversely correlated with population density. This ensured that there were sufficient males emerging, and surviving adult mortality, to guarantee fertilisation of the females which were more expensive to produce.

Journal

EcographyWiley

Published: Mar 1, 1987

References

  • Resource partitioning between unionid mussels in a Swedish lake outlet
    Brönmark, Brönmark; Malmqvist, Malmqvist
  • Why do males emerge before females? Protandry as a mating strategy in male and female butterflies
    Fagerström, Fagerström; Wiklund, Wiklund
  • Food sources and foraging tactics in tropical rain pools
    McLachlan, McLachlan
  • The annual cycle of Simulium erythrocephalum (Diptera: Simuliidae) at a site in Norfolk
    Post, Post
  • Thermal responses in the evolutionary ecology of aquatic insects
    Ward, Ward; Stanford, Stanford
  • The relationship between food particle size and larval size in Simulium noelleri Friederichs
    Wotton, Wotton

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