New Zealand Journal of Zoology abstracts
Density dependent prey-feeding time of Stethorus bifidus (Coleoptera:
Coccinellidae) on Tetranychus lintearius (Acari: Tetranychidae)
PAUL G. PETERSON
PETER G. MCGREGOR
Landcare Research
Private Bag 11052
Palmerston North, New Zealand
B. P. SPRINGETT
Massey University
Private Bag 11222
Abstract The gorse spider mite,
Tetranychus
lintearius, a biological control agent introduced into New Zealand to
control gorse, is often attacked by the endemic coccinellid,
Stethorus
bifidus. Predation by
S. bifidus has been suggested as a reason why
T. lintearius colonies collapse. For
S. bifidus predation to
regulate
T. lintearius populations, at least one component of its
numerical or functional response must result in an increased proportion of
mites being killed as mite density increases. Laboratory experiments showed
that feeding time (a sub-component of the functional response) decreased
markedly with increased
T. lintearius density. An increase in available
prey density from 3-25 mites/177 mm
2 led to an exponential
decrease in mean feeding time from 870 s to100 s. Furthermore,
despite
S. bifidus killing more mites, it extracted progressively
smaller proportions of the contents of each mite killed as mite density
increased.
Keywords Stethorus bifidus; beetle; Tetranychus
lintearius; spider mite; predation; functional response; feeding time; prey
density; biological control
Z99004
Received 12 February 1999; accepted 6 August 1999
PDF file of entire paper: medium quality (258K); (scanned from paper original: notes about this process)
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