video of male retreat from mated female in the parasitic
wasp Spalangia endius
King. B. H. 2008?
Effects of sex and mating status on who initiates contact in the parasitoid
wasp Spalangia endius (Hymenoptera:
Pteromalidae). Journal of Insect Behavior 21:387-393
In species without obvious aggression, individuals
may still vary in how likely they are to initiate contact with a conspecific.
In the parasitoid wasp Spalangia endius,
who was more likely to initiate contact during pair wise interactions depended
on sex and mating status. Specifically, more contacts
between the sexes were initiated by the male than by the female both when the
female was still virgin and when the female had already mated with a different
male. After a male mated with a given female, he still sometimes initiated
contacts with her, but no longer more often than she did. A male was more
likely to initiate contact when he was with a female than when he was with
another male, and he was more likely to retreat from a mated female than from a
male.
King, B. H. and Dickenson, R. M. 2008. Functional
and nonfunctional female receptivity signals in the parasitoid wasp Spalangia endius. Environmental Entomology. 37:782-786.
Abstract. In many taxa, females signal
during courtship when they are receptive. However, just because a female signals does not mean that the male responds to the signal.
This study examines female signaling of receptivity (readiness to copulate) and
male response in the parasitoid wasp Spalangia
endius
King, B. H. and Dickenson, R. M. 2008. A
behavioral study of the proximal mechanisms of male recognition of female
mating status in the parasitoid wasp Spalangia
endius (Hymenoptera: Pteromalidae). Annals of the Entomological Society of
Abstract. Mating preferences, including the proximate mechanisms of preferences,
have not been well-studied among parasitoid wasps. In the parasitoid wasp Spalangia endius
Fischer,
C. R. and King, B. H. 2008. Sexual
inhibition in Spalangia endius males
after mating and time for ejaculate replenishment. Journal of Insect Behavior 21:1-8.
Abstract. Although males are often stereotyped as always sexually responsive, a previous study with the parasitoid wasp Spalangia endius showed that males exhibit a post-mating decrease in sexual responsiveness. The present study examined the duration of the decrease and whether waiting to remate increased the amount of ejaculate that a male provided to his second mate. Mated males were back to being as sexually responsive as virgin males by about 5 min after mating. The amount of ejaculate that females received from already mated males was not significantly related to the duration between the male's first and second mating. The short-term decrease in sexual responsiveness of a mated male may prevent him from immediately trying to remate with the same female because it gives her time to get away.
King. B. H.
2007. The effect of exposure to conspecifics on restlessness in the parasitoid
wasp Nasonia vitripennis (Hymenoptera:
Pteromalidae). Canadian Entomologist 139:678-684.
Abstract. When habitat quality
is variable, there should be strong selection for the ability to detect and
respond to the variation. Adult females of the
parasitoid wasp Nasonia vitripennis (
King. B. H.
and M. E. Napoleon. 2006. Using effects of parasitoid size on fitness to test a
host quality model assumption with the parasitoid wasp Spalangia endius. Canadian
Journal of Zoology 84:1-5.
Abstract. How body size affects fitness of males relative to females is
relevant to understanding the evolution of sexual size dimorphism and maternal
sex ratio manipulation. In most parasitoid wasps, mothers oviposit
a greater proportion of daughters in larger hosts. The host quality model
describes how this may be adaptive. A major assumption of the model is that
host size has a greater effect on the fitness of daughters than sons. The
assumption has often been tested indirectly by examining effects of parasitoid
size on fitness because a parasitoid's size generally increases with the size
of the host on which it develops. The validity of this indirect method is
examined here for the parasitoid wasp Spalangia
endius
King. B. H. 2006. Mate
location and the onset of sexual responsiveness in the parasitoid wasp Spalangia
endius (Hymenoptera: Pteromalidae). Environmental Entomology 35:1390-1395.
Abstract. In some animals,
transformation to the adult stage occurs in a hidden location, such as a burrow
or a host. Males that can locate hidden females sooner, e.g., before they
emerge, may have a mating advantage, particularly if the females are ready to
mate. Whether males locate pre-emergent females and whether pre-emergent
females will mate was examined in the parasitoid wasp Spalangia endius
King, B. H. and H. Leaich.
2006. Variation in propensity to exhibit thanatosis
in Nasonia vitripennis. Journal of Insect Behavior 19(2):241-249.
Abstract. Thanatosis (death-feigning) has
rarely been documented for Hymenoptera but occurs in the parasitoid wasp Nasonia
vitripennis. The propensity to exhibit thanatosis
did not differ with age, sex, or food deprivation. Squeezing a female's abdomen
and contacting her antennae were equally likely to trigger thanatosis.
Dropping an object next to a female in order to cause substrate vibrations
never triggered thanatosis, and dropping a female
from a test tube rarely triggered thanatosis. Thanatosis was not seen during interactions between
females. There was some tendency for females to exhibit fewer thanatosis responses on white than on colored backgrounds.
Females that were least active had the greatest tendency to exhibit thanatosis.
King, B. H., and J. H. Ellison. 2006.
Resource quality affects restlessness in the parasitoid wasp Nasonia
vitripennis. Entomologia Experimentalis
et Applicata 118:71-76.
Abstract Optimal foraging theory, specifically
the marginal value theorem, predicts quicker leaving (shorter residence time)
from poorer patches. One proximal mechanism for achieving the leaving is that
exposure to lower quality resources may trigger increased restlessness
(proportion of time in locomotion). Which, if any, aspects of host quality
affect restlessness was examined in females of the parasitoid wasp Nasonia
vitripennis
King, B. H. and Fischer, C. R. 2005.
Males mate guard in absentia through extended effects of postcopulatory
courtship in the parasitoid wasp Spalangia endius. Journal of Insect
Physiology 51:1340-1345.
Abstract. The proximal mechanisms leading to monandry have been little-studied
in most insect orders, including Hymenoptera. In the parasitoid wasp Spalangia
endius, mated females are less attractive (less often mounted) than virgins
and are unreceptive (unlikely to allow copulation). Which aspects of mating are
responsible was tested by observing male responses toward females whose mating
had been interrupted at various stages. All females were allowed to receive precopulatory courtship and to open their genital aperture
to copulate. Then some were interrupted before copulation; some after
copulation but before postcopulatory courtship; and some were allowed to
complete postcopulatory courtship. Females that had copulated were not less
attractive than females that had not. In contrast, females that had received
postcopulatory courtship were clearly both less attractive and less receptive.
Thus, postcopulatory courtship functions as extended mate guarding, by making
the female less attractive and less receptive to subsequent males even after
the original male is no longer present. The effect of postcopulatory courtship
on female attractiveness was persistent but imperfect: when males were
presented sequentially to mated females, most but not
all males retreated without mounting, and a female could repulse more than
twenty males in succession.
King, B. H., Saporito, K. B.,
Ellison, J. H. and Bratzke, R. M. 2005.
Unattractiveness of mated females to males in the parasitoid
wasp Spalangia endius. Behavioural Ecology and
Sociobiology 52:17-24.
ABSTRACT Despite common stereotypes, males are
not always indiscriminate and eager when it comes to mating. In the parasitoid
wasp Spalangia endius, the initial response of males to females was
almost always one of apparent excitement; however, this was followed by a clear
preference for virgin females over mated females in both no choice and choice
situations. The no choice data were collected from videotapes of male-female pairs
of all possible combinations of mated and virgin individuals. Neither female
nor male mating status had a significant effect on likelihood of, or time
until, contact or male courtship fanning. However, a male's first retreat was
sooner when the female was mated than when she was virgin; mated males
exhibited their first retreat sooner than did virgin males; and mated females
were less likely to be mounted than were virgin females. In addition to the
videotapes, male choice experiments were performed. When given a choice of a
virgin and a mated female, both virgin and mated males were more likely to
mount and copulate with the virgin. The difference in response to virgin versus
mated females seemed to be less in virgin males than in mated males, perhaps
due to virgin males' greater eagerness to mate: when a virgin male and a mated
male were presented with a dead virgin female, the virgin male was usually the
first to respond to the female. That males preferentially retreated from and
avoided mounting mated females appears to be adaptive given that mated females
rarely copulated.
King, B. H. and J. A. D'Souza.
2004. Effects of constrained females on offspring sex ratios of Nasonia
vitripennis in relation to local mate competition theory. Canadian Journal of
Zoology 82:1969-1974.
Abstract. Empirical studies of how constrained females affect sex ratio are
few. Constrained females are those that can produce only sons, e.g., in haplodiploid species, females that have not mated or older
females that have used up their sperm. In the parasitoid wasp Nasonia
vitripennis (
Olbrich, D. L. and B. H. King. 2003. House fly and stable
fly (Diptera: Muscidae) pupae and their parasitoids
(Hymenoptera: Pteromalidae) in different habitats on a northern
ABSTRACT House fly and stable fly pupae were collected
during the summer from a dairy farm in northern
Baeder, J. and B. H. King. 2004. Associative learning of
color by males of the parasitoid wasp Nasonia
vitripennis (Hymenoptera:
Pteromalidae). Journal of Insect Behavior
ABSTRACT Males of the parasitoid wasp Nasonia vitripennis showed no
innate preference for blue versus yellow or for green versus brown. They
learned to associate color with mates, but their ability to do so depended on
the color used and the strength of the reward. Specifically, males learned to
associate brown or green with a reward of many virgin females. With fewer
females, fewer training periods, or mated females as the reward, males still
learned a preference for green, but not for brown. Males did not learn to
associate color with rewards of honey or water. Previous studies of color
preference and associative learning in parasitoid wasps have focussed almost entirely on females. This is the first
demonstration of associative learning in response to visual cues by male
parasitoid wasps.
King, B. H. 2002. Sex ratio response to conspecifics
in a parasitoid wasp: test of a prediction
of local
mate competition theory and alternative hypotheses. Behavioural
Ecology and
Sociobiology 52:17-24
ABSTRACT Maternal manipulation of offspring sex ratio in response to
conspecifics is considered in relation to sex ratio theory using the parasitoid
wasp Spalangia endius. Females produced a greater proportion of sons in
response to mated but not virgin females. This is the first demonstration of a
differential sex ratio response to virgin versus mated females and provides
support for local mate competition theory. More recent sex ratio models that
predict sex ratio responses to conspecifics, specifically constrained,
perturbation, and crowding models, were not supported. An increased proportion
of sons in response to another mated female occurred on the second day of
oviposition but not on the first, and the day effect resulted from experience
not age. When females oviposited alone after 2 d
exposure to another female, they still produced a greater proportion of sons
than if they had always been alone, but only if the other female was mated, not
if she was virgin. Females do not seem to assess the presence of virgin versus
mated females indirectly by using a low density of males or a long latency to
mate as an indicator for virgin females: neither affected offspring sex ratio.
That mated females adjusted their sex ratios in response to other mated females
but not virgin females or males may be due proximally to mated females not
often encountering the latter. Virgin females and males are not located as deep
in the oviposition substrate as mated females.
King, B. H. 2002. Offspring number and sex ratio
response to proportion of host sizes and ages
in the parasitoid wasp Spalangia cameroni (Hymenoptera: Pteromalidae). Environmental
Entomology 31:505-508. .
ABSTRACT In rearing parasitoids for biological control
releases and in natural populations, female parasitoids may
encounter variable distributions of host quality. Here I examine how the
proportion of hosts that are small versus large or old versus young affects sex
ratio and offspring production of the parasitoid wasp Spalangia cameroni Perkins (Hymenoptera: Pteromalidae)
parasitizing Musca domestica L pupae. With increasing proportion of
small hosts or old hosts, overall number of offspring did not significantly
decrease and the overall proportion that were male (i.e., from small and large
hosts combined) did not significantly increase. A greater proportion of sons
from small versus large and from old versus young hosts was not restricted to
the case of equal numbers of different host types. The proportion of sons
produced from small hosts as well as the proportion of sons from large hosts
decreased as the proportion of small hosts increased, and the proportion of
sons produced from young hosts decreased as the proportion of old hosts
increased. These results are relevant to recommendations for rearing S. cameroni for biological control releases and to testing
evolutionary sex ratio theory, specifically a combined host-quality and local
mate competition model.
King, B. H. 2002. Breeding strategies in females of
the parasitoid wasp Spalangia endius:
effects of mating status and body size.
Journal of Insect Behavior 15:181-193.
ABSTRACT Does the mating status or body size of
a female parasitoid wasp affect her host size choice or propensity to
burrow? In Spalangia endius, using smaller hosts appears to reduce a female's
cost of parasitization, but not her son's fitness.
However, virgin females, which produce only sons, did not preferentially
parasitize smaller hosts. Mated females also showed no host size preference.
Mated females burrowed more than virgins in the presence of hosts, although not
in their absence. Burrowing may reduce a mated female's harassment from males,
and not burrowing may increase a virgin female's chance of mating because males
avoid burrowing. Mating did not increase female longevity. Greater female size
increased offspring production of mated females burrowing for hosts, but not in
the absence of burrowing and not in virgin females. A female's size had no
significant effect on whether her first drill attempt was on a large or a small
host, or on the duration of her successful drills.
King, B. H. 2001. Parasitization
site on the host of the parasitoid wasp Spalangia endius
(Hymenoptera: Pteromalidae).
Environmental Entomology 30:346-349.
ABSTRACT Spalangia endius
King, B. H. 2000. Sperm depletion and mating behavior
in the parasitoid wasp Spalangia
cameroni (Hymenoptera:
Pteromalidae). The
ABSTRACT Mating behavior was examined in the
parasitoid wasp Spalangia cameroni.
Males attempted copulation
with both virgins and already mated females. Males attempted copulation
regardless of whether they still had sperm.
Already mated females rejected attempts to mate again but virgin females would
mate with males regardless of whether or
not they had sperm left. Males mated with 12-52 females before exhausting
their sperm supplies. Males that had mated
only once daily exhausted their sperm supplies in their late thirties (days
old), if ever; and males that had mated four times
daily exhausted their's at 7-13 days. Males
produced as many as 438 daughters from their first four matings.
57% (17 of
30) of females that had mated with virgin males exhibited a decrease in
proportion of daughters with age, presumably as a
result of sperm depletion. Whether or not a female depleted her sperm
supplies was not related to her size or the total
number of daughters that she had produced.
Oliai, S.E. and B. H. King. 2000. The
associative learning capabilities of the parasitoid wasp,
Nasonia vitripennis (Hymenoptera:
Pteromalidae). Journal of Insect Behavior 13:55-69.
ABSTRACT A parasitoid that can learn cues
associated with the host microenvironment should have an increased chance of
future host location and thereby increase its reproductive success. This
study examines associative learning in response to simultaneous exposure to the
colors yellow and blue in mated females of the parasitoid wasp Nasonia
vitripennis. Preference was measured as the proportion of time spent on a
color. When trained with one color rewarded with hosts and honey and the
other unrewarded, females showed an increase in preference for the rewarded
color with increasing number of training days (1, 3, and 7 days). Hosts
and honey together produced a slightly greater preference toward the rewarded
color than just hosts, which produced a greater preference than just
honey. When trained with a variable reward on one color and a constant
reward on the other, females preferred the color associated with the variable
reward when it was yellow, but not when it was blue. Thus, relative to no
reward, the presence of a variable reward decreased the strength of preference
toward the constantly rewarded color. Finally, females trained with
regular hosts on one color and used hosts on the other preferred the color
associated with the regular hosts when that color was blue but showed no
preference in the reverse situation. The presence of used hosts instead
of no reward did not increase the strength of preference for the color
associated with the regular hosts.
King, B. H. 2000. Sex ratio and
oviposition responses to host age and the fitness
consequences to mother and
offspring in the parasitoid wasp Spalangia endius. Behavioral
Ecology and Sociobiology 48:316-320
ABSTRACT In the parasitoid wasp Spalangia
endius more offspring and a greater proportion of daughters were
oviposited in, and emerged from, 0-day-old versus
3-day-old hosts. Offspring that developed on the younger hosts 1) were larger
at adulthood, 2) developed more quickly, 3) had higher survivorship to
adulthood, and 4) were more often able to chew their way out of the host. Sons
and daughters did not differ in how host age affected their size, development
rate, or survivorship. The greater proportion of daughters from the younger
hosts may be adaptive as described by the host quality model (a variant of the
Trivers and Willard hypothesis). It is adaptive if greater size or more rapid
development has a more positive effect on daughter's than son's fitness and the
positive effect is large enough to compensate for sons being trapped
disproportionately to daughters in the older hosts. Despite greater success at
drilling the younger hosts, mothers did not try to drill them sooner or more
often. Having previously oviposited on the older
hosts rather than the younger hosts had no detrimental effect on the mother's
subsequent longevity or offspring production.
King BH, Grimm KM,
Nasonia vitripennis
(Hymenoptera: Pteromalidae). Environmental Entomology 29(5):927-933
ABSTRACT. Effect of mating status on locomotor
activity was examined in females of the parasitoid wasp Nasonia vitripennis
(
Napoleon, M.E., and King, B.H.
1999. Offspring sex ratio response to host size in the parasitoid
wasp Spalangia endius. Behavioral Ecology and Sociobiology 46(5):
325-332.
ABSTRACT The host size
model, an adaptive model for maternal manipulation of offspring sex ratio, was
examined for the parasitoid wasp Spalangia endius. In a
hosts than sons, but only when mothers received both
small and large hosts simultaneously. The pattern appeared
to result from the mother's ovipositional
choice and not from differential mortality of the sexes during development.
If sex ratio manipulation is adaptive in the
developing on large hosts rather than through a
benefit to sons of developing on small hosts. Both female and male
parasitoids were larger when they developed on larger
hosts. For females, developing on a larger host (1)
increased offspring production, except for the largest
hosts, (2) increased longevity, (3) lengthened development,
and (4) had no effect on wing loading. For males,
development on a larger host had no effect on any measure of
male fitness - mating success, longevity, development
duration, or wing loading. In contrast, a strain from
showed no difference in the size of hosts from which
daughters versus sons emerged, although both female and
male parasitoids were larger when they developed on
larger hosts. These results together with previous studies of
Spalangia reveal no consistent connection
between host-size-dependent sex ratio and host-size-dependent
parasitoid size among strains of S. endius or
among species of Spalangia.
King, B.H. 1998. Host age response in the parasitoid
wasp Spalangia cameroni (Hymenoptera:
Pteromalidae). Journal of Insect Behaviour 11:
103-117.
ABSTRACT Female Spalangia cameroni
produced more offspring from younger house fly pupae, both when given a choice
of host ages and when not given a choice. Host age did not affect offspring
survivorship. Offspring were
larger when they had developed on younger hosts and
the effect was independent of offspring sex. Having
previously parasitized old hosts versus young hosts
did not reduce a female's production of offspring in subsequent
hosts. Females distinguished between young and old
hosts both in the light and in the dark. Females did not
distinguish between host ages prior to physical
contact with the host but could distinguish by the time they first
began exploring a host by tapping it with their
antennae; thus, they could distinguish before drilling into a host.
King BH, Crowe ML, Blackmore
MD.1998. Effects of leaf age response on oviposition and on offspring
fitness in the imported willow leaf
beetle Plagiodera versicolora
(Coleoptera: hrysomelidae).
Journal of
Insect Behavior 11:23-36.
Imported willow leaf beetles Plagiodera versicolora oviposit on willow leaves, and both larvae
and adults feed on the leaves. In the field, eggs were found on leaves
near the center of branchlets, and the number of eggs
per cluster was independent of leaf area and position. However, in the
laboratory, females chose young leaves over old leaves, for both oviposition
and feeding and choice did not rely on information on relative position or size
of leaves. Developing on young versus old leaves may provide both
advantages and disadvantages. In the laboratory, larvae developed more
quickly and attained greater adult weight when fed young versus old leaves,
perhaps because of increased mandibular wear of
larvae fed old leaves. However, in the field, survival of eggs was lower
on young versus old leaves. In the laboratory, rates of cannibalism and
survivorship to adulthood did not differ on young versus old leaves.
King, B.H. 1997. Effects of age and burial of house
fly (Diptera: Muscidae) pupae on parasitism by Spalangia
cameroni and Muscidifurax
raptor (Hymenoptera: Pteromalidae). Environmental Entomology 26(2):
410-415.
ABSTRACT The
parasitoids S. cameroni and M. raptor
commonly co-occur in nature and are sometimes released
together in efforts to control pest fly populations.
Laboratory experiments were conducted to determine how the
effectiveness of these wasps in killing house flies (Musca
domestica) and producing wasp progeny is affected by
the wasp species used, host burial and host age. For
effectiveness in killing flies, there was a significant 3-way
interaction. S. cameroni alone
was consistently more effective than Muscidifurax
raptor alone or than the 2 species
combined, regardless of host age and burial. However,
the greater effectiveness of S. cameroni was
most
pronounced for buried hosts and among unburied hosts
for young hosts. S. cameroni produced
offspring regardless
of host burial and host age. Host burial significantly
decreased production of S. cameroni offspring
only when S.
cameroni was present
and hosts were young. Host burial significantly reduced production of M.
raptor offspring in
all situations. M. raptor produced fewer
offspring from young hosts than from old hosts under all conditions,
producing no offspring from young buried hosts.
Combining S. cameroni and M. raptor did
not increase their
effectiveness at killing hosts. Being with the other
species versus a conspecific had no significant effect on
production of M. raptor offspring and increased
production of S. cameroni offspring only from
young buried hosts.
King, B.H. 1996. Sex ratio responses to other
parasitoid wasps: multiple adaptive explanations. Behavioral Ecology and
Sociobiology 39: 367-374.
ABSTRACT In an effort
to distinguish among adaptive models and to improve our understanding of
behavioral
mechanisms of sex ratio manipulation, this study
examines sex ratio response to other wasps in the solitary
parasitoid wasp Spalangia cameroni.
Relative to when alone, females produced a greater proportion of sons in the
presence of conspecifics, regardless of whether the
conspecifics were female or male. In addition, females
produced a greater proportion of sons after a day with
a conspecific male, and after a day with a conspecific
female but only if the females had been ovipositing.
Relative to when alone, females did not produce a greater
proportion of sons in the presence of females of the confamilial Muscidifurax
raptor or in response to hosts that had
already been parasitized by a conspecific. A
combination of evolutionary models may explain S. cameroni's
sex
ratios. An increased proportion of sons in response to
conspecific females is common among parasitoid wasps and
is usually explained by local mate competition (LMC)
theory. However, such a response is also consistent with the
perturbation model, although not with the constrained females model. The response to conspecific males is not
consistent with LMC theory or the perturbation model
but is consistent with the constrained females model.
King, B.H. 1996. Fitness effects of sex ratio
response to host quality and size in the parasitoid wasp Spalangia cameroni. Behavioral Ecology 7: 35-42.
ABSTRACT The parasitoid
wasp Spalangia cameroni oviposited
a greater proportion of daughters in stable fly pupae
than in house fly pupae, even controlling for stable
flies being smaller than house flies. Sex ratio manipulation in
response to host quality has been modeled as being
adaptive through an effect of host quality on the size and hence
offspring production of daughters. S. cameroni's response to host species may instead be
adaptive through an
effect on larval survivorship, the development time of
daughters, and the size of sons. There was greater survival of
daughters than sons on stable flies. Controlling for
host size, development time of daughters was about 2% less on
stable flies than on house flies. The decrease in
development time corresponds to a 2% increase in fitness as
estimated by r, the intrinsic rate of increase, and is
equivalent to about a 9% increase in offspring production. Sons
were about 2% larger from house flies than stable
flies, which may increase offspring production by up to 3%.
There was no consistent effect of host species on size
of daughters or development time of sons. In addition to the
response to host species, mothers oviposited a greater proportion of daughters in
larger stable fly hosts. Whether
this behavior is adaptive is unclear. Although
offspring were larger when they developed on larger stable flies, the
rate of increase was less for daughters than for sons.
Effects of stable fly size on offspring development time were
negligible.
King, B.H. and King, R.B. 1995. Sibmating
and its fitness consequences in the parasitoid wasp Spalangia
cameroni
(Hymenoptera: Pteromalidae). Journal of Insect Behavior 8(5): 723-730.
Notes: Spalangia cameroni showed no preference
for or against mating with brothers as evidenced by no significant difference
in likelihood of mating with brothers versus nonbrothers
in the choice experiment and as evidenced by no difference in duration until
mounting or duration until mating in either the choice or no choice
experiments. There was no evidence that sibmating
affected fitness as measured by number of adult offspring. Offspring sex
ratio also was unaffected by sibmating.
King, B.H., Crowe, M.L. and Skinner, S.W. 1995.
Effect of host density on offspring sex ratios and behavioral interactions
between females in the parasitoid wasp Nasonia vitripennis (Hymenoptera:
Pteromalidae). Journal of Insect Behavior 8: 89-102.
ABSTRACT Pairs of
females of the parasitoid wasp Nasonia vitripennis were videotaped with
one or two hosts. The presence of an additional host decreased the number
of interactions between females but had no measured effect
on the nature of the interactions, i.e., on whether
the interaction involved physical contact or occurred while one of
the females was parasitizing a host. The number of
hosts did not itself affect offspring sex ratios but did influence
which other factors were correlated with sex ratio.
When there was one host, the proportion of sons was more
positively correlated with utilization of previously
drilled holes than with female-female interactions, whereas when
there were two hosts, the reverse was true.
Parasitizing an already parasitized host appeared to affect a female's
sex ratio beyond any effects of the physical presence
of another female: When two hosts were present, the
proportion of sons was greater from hosts parasitized
by both females than from hosts parasitized by only one
female. The observation that parasitizations
in previously drilled holes and female-female interactions are correlated
with sex ratios is consistent with previous studies;
however, that these relationships are host density dependent is a
new result and remains unexplained.
King, B.H. 1994. Effects of host size experience on
sex ratios in the parasitoid Spalangia cameroni.
Animal Behaviour 47(4): 815-820.
ABSTRACT The sex ratio
response of a female parasitoid wasp Spalangia cameroni
is affected both by the size of the host that she is parasitizing and by
the size of hosts that she has previously encountered. When given small and
large
hosts simultaneously, S. cameroni
females oviposit a greater proportion of sons in
the small hosts (King, 1988,
Evolution, 42, 1190-1198). Two hypotheses were tested
to examine how a female's offspring sex ratio is affected
by her previous host size experience. First, van den
Assem et al.'s (1984, Neth. J. Zool.,
34, 33-62) life
expectancy hypothesis was tested. This hypothesis
suggests that when females encounter only small hosts, the
production of daughters will be inhibited initially
and then, as no large hosts become available, production of
daughters will increase. This hypothesis was not
supported. The second hypothesis tested was that in their sex ratio
responses, females will judge hosts as small or large
relative to other hosts encountered. This hypothesis was
supported under some conditions. Females judged hosts
as small or large relative to previously encountered hosts
when parasitizing large hosts and when the previous
experience with hosts was immediately prior. When a female
received only one host size, females that were given small
hosts produced either a greater proportion of sons or the
same sex ratio as females that were given large hosts.
King, B.H. 1994. How do female parasitoid wasps
assess host size during sex-ratio manipulation? Animal Behaviour
48(3): 511-518.
ABSTRACT As in many
parasitoid wasps, Spalangia cameroni females
oviposit a greater proportion of daughters in large hosts than in small hosts.
How females assess host size for this sex-ratio manipulation was examined: do
females require visual cues and do they use exposed
surface area or volume or duration required to drill into a host
prior to oviposition? Visual cues are not necessary;
in the dark, females still produced a greater proportion of
daughters in large hosts than in small hosts. To
examine whether females use exposed surface area or volume to
estimate host size, proportion of daughters was
compared between unburied hosts and hosts that had been
half-buried either horizontally or vertically. Burying
hosts did not interfere with host-size assessment for sex-ratio
response; sex ratios did not differ between partially
buried hosts and unburied hosts of the same size. Females do
not appear to use duration required to drill into a
host prior to oviposition to assess a host's resources. Drill
duration was not consistently longer or shorter for
the types of hosts in which daughters versus sons tended to be
oviposited. Specifically, a
greater proportion of daughters were oviposited in
large hosts than in small hosts and in
young hosts than in old hosts. Drill duration was
longer in large hosts than small hosts but was shorter in young
hosts than old hosts. The greater average drill
duration observed for daughters suggests that daughters may be
more costly to produce than sons.
King, B.H. and Lee, H.E. 1994. Test of the adaptiveness of sex ratio manipulation in a parasitoid
wasp.
Behavioral Ecology and Sociobiology 35(6): 437-443.
ABSTRACT In behavioral
ecology it is generally assumed that behavior is adaptive. This assumption is
tested here for sex ratio manipulation in
response to host size in the parasitoid wasp Spalangia cameroni.
Females produce a
greater proportion of daughters on larger hosts. If
this behavior is adaptive, it is not through a positive effect of host
size on the fitness of daughters, as theory suggests
and as found for other species. Females that developed on
larger hosts were not more successful at drilling into
hosts, were not more successful at interspecific
competition for
hosts, and did not have greater dispersal ability as
measured by wing loading (weight/area of wing and thorax). The
possibility that S. cameroni's
sex ratio manipulation may be adaptive through a negative effect of host size
on the
fitness of sons cannot be ruled out. Relative to males
from larger hosts, males from smaller hosts had lower wing
loading and thus potentially greater dispersal
ability. The actual effect of wing loading on fitness remains to be
tested.
King, B.H. and King, R.B. 1994. Sex ratio
manipulation in response to host size in the parasitoid wasp Spalangia cameroni: is it adaptive? Behavioral Ecology 5(4):
448-454.
ABSTRACT Many species
of parasitoid wasps produce a greater proportion of sons in small than in large
hosts. As
described by the host-size model, natural selection is
becoming a standard explanation for the evolution of this
phenomenon. We examined a critical assumption of the
host-size model, that host size has a more positive effect on
female than on male reproductive success. In
laboratory experiments with the parasitoid wasp Spalangia cameroni,
females that developed on larger hosts contained more
eggs at emergence. However, more eggs did not translate
into more offspring, at high or low density and
regardless of whether a female had to burrow to reach hosts. The
size of host on which a female developed was also
unrelated to her longevity, regardless of the presence or
absence of hosts. The size of host on which a male
developed had no effect on his sperm production or ability to
inseminate females, regardless of whether insemination
ability was measured by the amount of sperm transferred to
a female, by the proportion of a male's mates that
produced any daughters, or by the proportion of daughters that a
male's mates produced. Thus, despite data on multiple
measures of fitness under a range of conditions, sex ratio
manipulation in response to host size in S. cameroni does not appear to be adaptive, and another
explanation is
needed.
King, B.H. 1993. Sex ratio
manipulation by parasitoid wasps. pp. 418-441. In: Wrensch
DL, Ebbert, M
(eds). Evolution and Diversity of Sex Ratio in Insects and Mites.
Chapman and Hall,
SUMMARY At least some parasitoid wasp species manipulate offspring sex ratio in
response to environmental conditions. Most, but not all, species of
parasitoid wasps that have been examined produce a greater proportion of sons
in smaller hosts, as predicted by host quality models. The more than
forty species meeting this prediction come from thirteen different families and
include primarily solitary species, but also some gregarious and facultatively gregarious species. Species meeting the
prediction include primarily parasitoids of nongrowing
hosts, but also some parasitoids of growing hosts.
In addition, most, but not all, species of parasitoid
wasps that have been examined produce a greater proportion of sons in the
presence of other mothers than when alone, as predicted both by LMC models and
by a host quality model for gregarious species. The sixteen species
meeting this prediction come from five different families and include both solitary
and gregarious species. Most, if not all, of these solitary species
parasitize clumped hosts.
Differential mortality of the sexes has been ruled out
as the cause of the relationships between sex ratio and host size and between
sex ratio and number of mothers for nine and nine species respectively.
Thus, in these species, mothers are known to be manipulating their offspring
sex ratios in response to environmental conditions.
In order to understand the evolution of sex ratio
manipulation in parasitoid wasps, we need more empirical information regarding
constraints on manipulation and the assumptions of models of adaptive
manipulation. Insufficient data on the assumptions of sex ratio models
and the extent to which limitations on manipulation occur mean that
quantitative predictions about sex ratio manipulation are tentative at
best. Fortunately, the models' qualitative predictions are somewhat
robust to the assumptions and limitations.
King, B.H. 1993. Flight activity in the parasitoid wasp
Nasonia vitripennis (Hymenoptera: Pteromalidae). Journal of Insect
Behavior 6(3): 313-321.
ABSTRACT Flight
activity in females of the parasitoid wasp Nasonia vitripennis (
flight (with no pauses of more than 5 s) was more than
2 h long. Mating status had a significant and large effect on
flight: mated females flew twice as long as virgin
females. There also was a slight but significant effect of age on
flight, with 3-day-old females being less likely to
fly than 1-day-old females. Flight duration was not affected by
prior exposure to other females, to honey, or to a low
or a high host density.
King, B.H. 1993.Sequence of offspring sex production
in the parasitoid wasp, Nasonia vitripennis, in response to unparasitized versus parasitized hosts. Animal Behaviour 45: 1236-1238.
Notes: Sequence of offspring sex production differed between the unparasitized and parasitized host treatments. In unparasitized hosts, the proportion of sons that females
produced increased with clutch size; whereas in parasitized hosts, the
proportion of sons decreased. In unparasitized hosts,
the number of daughters increased steadily with increasing clutch size; sons
were not produced in clutches of less than four. In contrast, in
parasitized hosts, the number of sons increased steadily; daughters were not
produced in clutches of less than eight. Offspring sex ratio was more variable
in parasitized than in unparasitized hosts.
King, B.H. and Seidl, S.E. 1993. Sex ratio response of the parasitoid wasp Muscidifurax
raptor to other females. Oecologia 94(3):
428-433.
Summary. This study
examines the sex ratio response of the parasitoid wasp Muscidifurax
raptor to conspecific and confamilial females in
relation to two groups of functional sex ratio models, local mate competition
and host quality models. In some but not all experiments, M. raptor females
produced a greater proportion of sons in the presence of a conspecific female
than when alone, and this sex ratio effect carried over for a day after the
females were isolated from each other. M. raptor females also produced a
greater proportion of sons in the presence of a female of the confamilial parasitoid Spalangia cameroni
than when alone (although only on the second day of exposure to S. cameroni, not on the first). M. raptor's sex ratio
increase in the presence of conspecifics is consistent with local mate
competition models but not with host quality models because the presence of a
conspecific female did not cause there to be more, and thus potentially
smaller, offspring developing per host. In contrast, the presence of a S.
cameroni female did cause there to be more offspring
developing per host than when a M. raptor female was alone; thus, M. raptor's
sex ratio increase in the presence of S. cameroni may
be explained by host quality models. An alternative explanation for the
sex ratio increase in response to confamilials is that only a sex ratio
response to conspecifics may be adaptive, due to local mate competition; but M.
raptor females may be unable to distinguish between conspecific and S. cameroni females.
Seidl, S.E. and B.H. King. 1993. Sex ratio
response to host size in the parasitoid wasp Muscidifurax
raptor. Evolution 47:1876-1882.
Notes: The proportion of sons produced by M. raptor was greater from small than
from large hosts as predicted by the host size model. There was no evidence of
differential mortality, suggesting that the greater proportion of sons from
small versus large hosts results from maternal manipulation of sex ratio at the
time of oviposition. Although the host size model prediction that a greater
proportion of sons will be oviposited in small than
in large hosts was supported, the model's assumption that host size has a more
positive effect on the reproductive success of daughters than sons was not
supported. Host size did not affect wasp size. Furthermore, there
was no evidence that host size affects either female or male reproductive
success. Female M. raptor did not exhibit a positive relationship between host
size and longevity or offspring production, regardless of how offspring
production was measured. Male M. raptor did not exhibit a positive relationship
between host size and longevity or mating success.
King, B.H. 1992. Sex-ratios of the wasp Nasonia
vitripennis from self-versus conspecifically-parasitized
hosts: local mate competition versus host quality models. Journal of
Evolutionary Biology 5(3): 445-455.
ABSTRACT Sex ratio
patterns in the parasitoid wasp Nasonia vitripennis are frequently cited in
support of a major
group of evolutionary sex ratio models referred to as
local mate competition (LMC) models. It has been shown
repeatedly that, as predicted by LMC models, females
generally oviposit a greater proportion of sons in previusly
parasitized hosts that in unparasitized
hosts. However, this sex ratio pattern is also a prediction of another group of
sex ratio models, the host quality models. Here I test
a prediction of LMC models that is not also a prediction of
host quality models: a female should produce a greater
proportion of sons when she parasitizes a host previously
parasitized by a conspecific female than when she
parasitizes a host previously parasitized by herself.
Females
made this predicted distinction between self- and conspecifically-parasitized hosts under some conditions.
There
was no evidence that a female recognizes a
self-parasitized host when her exposure to the host is interrupted by
exposure to an unparasitized
host, or that a female can distinguish between hosts parasitized by sisters
versus
nonsisters.
King, B.H. and Skinner, S.W. 1991. Proximal
mechanisms of the sex ratio amd clutch size responses
of the wasp Nasonia vitripennis to parasitized hosts. Animal Behaviour 42: 23-32.
ABSTRACT Female Nasonia
vitripennis lay fewer eggs and increase the proportion of male offspring when
ovipositing
in hosts that have been previously parasitized
compared with unparasitized hosts. This study
examines the location
and nature of the cues that females use in these
clutch size and sex ratio decisions. Neither the sex ratio nor the
clutch size response relies on chemical cues on, or a
hole drilled in, the outer shell of the host (the puparium).
Rather, the cues for both responses appear to be
associated with the host pupa. Females manipulate clutch size but
not sex ratio in response to host death: the number of
eggs laid on dead hosts is significantly lower than on either
live hosts or previously parasitized hosts. In
addition, the cues that females use for sex ratio manipulation, but not
for clutch size manipulation, are local: sex ratio
cues are not detected from the end of the host that is opposite the
site of parasitization;
clutch size cues are. The cues that females use may constrain their sex ratio
and clutch size
manipulation abilities.
King, B.H. and Skinner, S.W. 1991. Sex
ratios in a new species of Nasonia with fully-winged males.
Evolution 45: 225-228.
Notes: We present results showing that N. giraulti does
manipulate offspring sex ratio in response to number of other mothers present,
but that N. giraulti produces even more, not less,
female-biased sex ratios than N. vitripennis.
King, B.H. 1991. No intersexual
differences in host size and species usage in Spalangia endius
(Hymenoptera: Pteromalidae).
Spalangia endius were collected from fly pupae, primarily house fly and stable
fly, from a poultry house in
King, B.H. 1991. A field study of host
size effects on sex ratio of the parasitoid wasp Spalangia cameroni. American
I examined aspects of Charnov et al.'s (1981) host-size model for the
parasitoid wasp Spalangia cameroni, using collections
of fly pupae (hosts) from a poultry house. The model predicts that female
parasitoid wasps should emerge from larger hosts than males. This prediction
was supported for two collection dates in which only one host species, house
flies, was parasitized by S. cameroni. The prediction
was not supported either within host species or combining host species for the
collection date in which both house flies and stable flies were parasitized. In
fact, female S. cameroni emerged from smaller stable
fly pupae than did males. The prediction of the host-size model also was not
supported on a between host species basis. Though stable fly pupae are
significantly smaller than house fly pupae, the sex ratio (proportion of males)
of S. cameroni emerging from stable flies was not
significantly greater than from house flies. Contrary to expectations, field
data showed no positive relationship between host size and female wasp size
either within or between host species. Laboratory experiments indicated that
female S. cameroni judge host size relative to the
size of other hosts encountered, as predicted based on the significant temporal
variation found in the host size distribution in the field.
King BH. 1990. Interspecific differences in host (Diptera: Muscidae) size and species usage among
parasitoid wasps Hymenoptera:
Pteromalidae) in a poultry house. Environmental
Entomology
19:1519-1522.
ABSTRACT. Fly pupae, primarily house fly (Musca domestica Linnaeus) and stable
fly (Stomoxys calcitrans
(Linnaeus)) (Diptera: Muscidae), were collected from a
poultry house in northern
King BH. 1990. Sex
ratio manipulation by the parasitoid wasp Spalangia cameroni
in response to host
age: a test of the host-size model.
Evolutionary Ecology 4:149-156.
ABSTRACT A sex ratio response to host resources as
measured by external host dimensions has been demonstrated in many parasitoid
wasps, including Spalangia cameroni. The responses
generally are in the direction predicted by sex ratio theory, specifically the
host size models. Here I show that female S. cameroni
also respond to differences in resource availability not associated with
changes in external host dimensions, and this response is in the direction
predicted by host size models. When given old and young hosts simultaneously,
female S. cameroni oviposit a greater proportion of
sons in old than in young host pupae, at least for 0-day old versus 3-day old
hosts. Old hosts weigh less than young hosts but are not significantly
different in external width. Thus it appears that the offspring sex ratio
response may result from mothers detecting physical or chemical changes within
the host which are associated with host age. No evidence is found that the
manipulation in response to host age has been selected for via an effect of
host age on wasp size: there was no significant effect of host age on either
male or female wasp size. A second prediction of the host size models is also
supported by this study: when each female is presented with only a single host
age, rather than two host ages simultaneously, host age has no effect on
offspring sex ratio.
King BH. 1989. Host
size-dependent sex ratios among parasitoid wasps: Does host growth matter?
Oecologia
78:420-426.
Summary. Waage's (1982)
hypothesis that host-size-dependent sex ratios will occur in parasitoids of nongrowing hosts and not in parasitoids of growing hosts is
examined using published data on parasitoid wasps. Waage's
hypothesis is supported as a general, but not absolute, rule: among solitary
parasitoid wasps, a significantly greater proportion of parasitoids of nongrowing than of growing hosts show some evidence of
host-size-dependent sex ratios (85% versus 45%, G = 5.28, p < 0.05). The
premise of Waage's hypothesis--that for parasitoids
which develop in a growing stage, host size at oviposition is not a good
predictor of the amount of resources available to the developing parasitoid--is
also examined. It is suggested that across host species Waage's
premise will hold for some, but not all, parasitoids of growing hosts. Likely
exceptions to Waage's premise, and thus his
prediction, are discussed. Parasitoids of growing hosts which are expected to
have evolved host- size-dependent sex ratios include parasitoids which utilize
a narrow size range of host species, parasitoids which can distinguish among
host species by some criterion other than size, and parasitoids which utilize
host species whose susceptible instars do not overlap in size.
King BH. 1989. A test of local mate competition theory with a solitary
species of parasitoid wasp,
Spalangia cameroni.
Oikos 55:50-54.
The effect of conspecific females on offspring sex ratio was examined in the
parasitoid wasp Spalangia cameroni. In the presence
of a second female, females increased the proportion of sons they produced
relative to when they were alone, as predicted by local mate competition
theory. However, females did not seem to differentiate between two and more
than two females: offspring sex ratios from groups of two, four, six, and ten
females were not significantly different. The trace odor of another female was
not a sufficient cue for females to increase the proportion of sons they
produced. Results indicate that for species with large interfemale
variation in offspring sex ratio, it is preferable to test how the presence of
other females affects offspring sex ratio by looking for changes within individual
females rather than by comparing different-sized groups of females.
King BH. 1988. Sex
ratio manipulation in response to host size by the parasitoid wasp Spalangia
cameroni:
a laboratory study. Evolution 42:1190-1198.
Abstract--The prediction of Charnov et al.'s (1981) host-size model that there
should be a negative relationship between host size and wasp sex ratio
(proportion sons) was supported for Spalangia cameroni,
a solitary parasitoid wasp. The relationship was shown to be a result of
offspring sex manipulation by females in response to host size rather than a
result of differential mortality of the sexes. A major assumption of the
host-size model is that host size has a greater effect on the ultimate
reproductive success of emerging female wasps than of males. This assumption
was not supported. Host size had a positive effect on the size of both male and
female S. cameroni. However, there was no effect of
host size or wasp size on several aspects of reproductive success--production
of offspring by females, ability of males to compete for mates, and male and
female longevity. Host size may differentially affect the reproductive success
of female and male wasps through effects on other aspects of reproductive
success. Tests of the assumptions of offspring sex- ratio manipulation
hypotheses are scarce but critical, not only for parasitoid wasps, but also for
other organisms.
King BH. 1987.
Offspring sex ratios in parasitoid wasps. Quarterly Review of Biology 62:367-396.
ABSTRACT Laboratory and field studies on about 100 species in sixteen families
indicate that several factors can influence offspring sex ratios in parasitoid
wasps. For many species, offspring sex ratio increases with one or more of the
following: 1) maternal age at ovipositing or the amount of time since
insemination, 2) the age of the male parent or the number of times he has
copulated, 3) extreme temperature, 4) decreasing host size, age, or quality, 5)
female wasp density, and 6) the number of progeny per host. Other factors which
have been shown to affect offspring sex ratios in some species include: 1)
number of hours since insemination, 2) genetic factors, 3) maternal size, 4)
maternal diet, 5) polyembryony, 6) photoperiod and
relative humidity, 7) host sex, and 8) host density.
These factors may affect offspring sex ratios through females
manipulating fertilization of their eggs or through other mechanisms such as
differential mortality or changes in sperm availability. Theoretical
development has focused primarily on females manipulating their offspring sex
ratios in response to host size and/or to female density. Host size models
predict a negative relationship between offspring sex ratio and host size.
These models assume that host size has a greater effect on the reproductive
success of females than of males. LMC models predict a positive relationship
between offspring sex ratio and female density. A major assumption of these
models is that males mate primarily in their natal area. For each model, most
of the species examined meet the model's general prediction. However, the
models have been rigorously tested for only a few species. Such testing
requires supporting data on the assumptions made and examination of alternative
explanations, particularly sex ratio differences due to differential mortality.
Hurlbutt BL.
1987. Sexual size dimorphism in parasitoid wasps. Biological Journal of the Linnean
Society 30:63- 89.
Sexual dimorphism in body length and proportion of overlap between the ranges
of body length for males and females were estimated for 361 species of
parasitoid wasp from 21 families. In most species, females are generally larger
than males, though the range of male and female sizes overlap.
Species in the family Ichneumonidae differ significantly
from species in other families in three ways: (1) ichneumonids
on average are larger, (2) in most species, females are generally smaller than
males, and (3) on average, proportion overlap between the ranges of body length
for males and females is greater. At present, there is a paucity of life
history data on parasitoid wasp species for which size dimorphism is known.
Thus it is not clear why ichneumonids differ among
species in other families. Possible evolutionary explanations for variation in
dimorphism among parasitoid wasp species are discussed.
Hurlbutt BL. 1987. Sex ratio in a
parasitoid wasp, Spalangia cameroni(Hymenoptera: Pteromalidae).
Ph.D. dissertation,
Purdue University, West Lafayette,