Sensory Ecology of Arthropods Utilizing Plant Infochemicals
265
1999), the nature of the active chemicals is known in only few cases. A "minimal
blend" that elicits attraction (out of the often chemically complex odor blend
emitted) could be defined for the specialized predaceous mite Phytoseiulus
persimilis (Dicke et al. 1990), the braconid wasp Cotesia marginiventris (Turlings
and Fritzsche 1999) and the aphid parasitoid Aphidius ervi (Du et al. 1998). For
the braconid Microplitis croceipes individual GLVs were found to elicit an upwind
response in windtunnel assays (Whitman and Eller 1990, 1992). In these cases,
however, the complex blend was found to be more attractive than the reduced
"synthetic blend", indicating that the complete signal is not yet known. Indeed, in a
detailed analysis it was found that some compounds in the blend may mask the
attractive components (Turlings and Fritzsche 1999).
3 Conclusions
Plants produce an overwhelming amount of so-called secondary compounds, both
volatiles and nonvolatiles. These compounds can be exploited by arthropods when
searching for food or oviposition sites. Effects of plant chemicals on arthropods
have long been studied for herbivorous arthropods exclusively. Accordingly, there
is extensive knowledge on both the sensory perception and behavioral responses.
Herbivorous arthropods are predominantly specialists and plant chemistry is one of
the important factors - though not the only factor - mediating host plant selection
(e.g., Bernays and Chapman 1994; van Loon 1996; Schoonhoven et al. 1998).
Most of the information available is on non-volatile plant chemicals. Carnivorous
arthropods also use plant chemicals when searching for their herbivorous
arthropod victims. Herbivore-damaged plants emit volatiles utilized by
carnivorous arthropods to locate the herbivores that inflicted the damage. The
blend emitted by herbivore-damaged plants may differ quantitatively (blends of
same compounds but at different ratios) or qualitatively (blends composed of
different sets of chemicals).
The specificity of herbivore-induced plant volatiles can convey information that
enables carnivores to discriminate among herbivore species. The ability to
discriminate often is acquired through learning. Learning seems to be more
important in the case of quantitative differences than in the case of qualitative
differences in volatile blends (Vet et al. 1998). Although some information is
accumulating on the sensory physiology of carnivorous arthropods, very little
information is available yet on the perception of and on the behavioral response to
blends that differ in composition. However, this information is essential if we want
to better understand how carnivorous arthropods evaluate complex odor blends so
as to efficiently locate their herbivorous victims.
265
1999), the nature of the active chemicals is known in only few cases. A "minimal
blend" that elicits attraction (out of the often chemically complex odor blend
emitted) could be defined for the specialized predaceous mite Phytoseiulus
persimilis (Dicke et al. 1990), the braconid wasp Cotesia marginiventris (Turlings
and Fritzsche 1999) and the aphid parasitoid Aphidius ervi (Du et al. 1998). For
the braconid Microplitis croceipes individual GLVs were found to elicit an upwind
response in windtunnel assays (Whitman and Eller 1990, 1992). In these cases,
however, the complex blend was found to be more attractive than the reduced
"synthetic blend", indicating that the complete signal is not yet known. Indeed, in a
detailed analysis it was found that some compounds in the blend may mask the
attractive components (Turlings and Fritzsche 1999).
3 Conclusions
Plants produce an overwhelming amount of so-called secondary compounds, both
volatiles and nonvolatiles. These compounds can be exploited by arthropods when
searching for food or oviposition sites. Effects of plant chemicals on arthropods
have long been studied for herbivorous arthropods exclusively. Accordingly, there
is extensive knowledge on both the sensory perception and behavioral responses.
Herbivorous arthropods are predominantly specialists and plant chemistry is one of
the important factors - though not the only factor - mediating host plant selection
(e.g., Bernays and Chapman 1994; van Loon 1996; Schoonhoven et al. 1998).
Most of the information available is on non-volatile plant chemicals. Carnivorous
arthropods also use plant chemicals when searching for their herbivorous
arthropod victims. Herbivore-damaged plants emit volatiles utilized by
carnivorous arthropods to locate the herbivores that inflicted the damage. The
blend emitted by herbivore-damaged plants may differ quantitatively (blends of
same compounds but at different ratios) or qualitatively (blends composed of
different sets of chemicals).
The specificity of herbivore-induced plant volatiles can convey information that
enables carnivores to discriminate among herbivore species. The ability to
discriminate often is acquired through learning. Learning seems to be more
important in the case of quantitative differences than in the case of qualitative
differences in volatile blends (Vet et al. 1998). Although some information is
accumulating on the sensory physiology of carnivorous arthropods, very little
information is available yet on the perception of and on the behavioral response to
blends that differ in composition. However, this information is essential if we want
to better understand how carnivorous arthropods evaluate complex odor blends so
as to efficiently locate their herbivorous victims.