ProQuest Dissertations - The University of Arizona Campus Repository

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Xfini review
Host marking behavior in phytophagous insects and parasitoids
Cesar R. Nufio'^ & Daniel R. Papaj--'
Deparliiienr of EnioitwIoi'yK Depunment of Eculu^y anil Evoltiliimarv Bioltiny. Center fur Inxecl Science', and
the Inlerdisciplinary Degree Proi>nim in Insect Science^. University of Arizona. Tucson. .42 S5721. USA
ACL-cplcd: January 4. 2)K)I
Ke\ wnrtis: marking pheromone. oviposition deterring pheromone. oviposiiion behav ior, animal communication,
competition, superparasitism. para.sitotds
.AbKlracI
Oviposition behavior m phvtophugous insects and entomophagous parasitoids is iiften muditied by the presence
ot' conspecitic brood (eggs and larvae). Often, females avoid laying eggs on or in hosts bearing brood, a behavior
that acts to reduce the level of competition suffered by their offspring. .Avoidance of uccupicd hosts is typically
mediated by cues and/or signals a.ssociated with broixl. In this article, we review the role of Marking Pheromones
(MPs) as signals of brood presence in both phytophagous and entomophagous in.sects. We place information about
the function and evolution of MPs in theconte.it of recent theory in the field of animal communication. We highlight
the dynamics of host-marking systems and dl.scuss how effects of MPs vary according to factors such as female
experience and egg toad. We al.so examine variation in the form and function of MP communication across a
variety of insect taxa. While studies of MP communication in phytophagous insects have focused on the underlying
behavioral mechanisms and chemistry of MP communication, studies in entomophagous insects have focused
on the functional aspects of MPs and their role in "decision-making' in insects. We argue that an approach that
incorporates the important contributions of both of these somewhat independent, but complementary areas of
research will lead to a more complete understanding of MPs in insects. Finally, we suggest that .MP systems are
model svstems for the studv of animal sienalins and its evolution.
Introduction
Cues versus signals in assessment ofhrood presence
The oviposition behavior of phytophagous and parasitic
insects is often mixiihed by the presence of
conspecific brood (eggs and larvae). Typically, females
avoid depositing eggs on previously exploited
host re.sources. a behavior thought to reduce competition
suffered by their offspring iProkopy. 1981a).
Tlie stimuli permitting females to di.stinguish between
occupied and unoccupied hosts can be categorized as
either cues or signals (Seeley. I99S) i see Table I for
definitions of terms u.sed throughout manuscript). The
distinction is made on evolutionary grounds. Whereas
a signal is presumed to have evolved to convey information
from a sender to a receiver, a cue is a product
of selection on a trait other than communication and
conveys information only incidentally. Females of a
variety of species, for example, as.sess the pre.sence of
conspecitic brood on the basis of vi.sual or tactile stimuli
a.s.sociated with eggs (Rausher. 1979: Williams &
Gilbert. 198k Shapiro. 1981;Takasu & Hirose. 1988)
or larvae (Mappes & Makela. 1993). It is not obvious
that the stimuli involved have been shaped by selection
to enhance their detectability: as such, these stimuli
might best be described as cues of brood presence.
Cues of brood presence need not be directly produced
by the juvenile stages themselves. For some
phytophagous insects, for example, larval fra.ss deters
oviposition on infested hosts. Some investigators have
found that the deterrent compounds are unaltered plant
con.stituents. and not metabolic by-producLs or compounds
actively produced by the larvae them.selves
(Mitchell & Heath. 1985). .As such, thev would be
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