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Results
Methods
Materials and
methods
Be brief, and opt for photographs or drawings
whenever possible to illustrate organism,
protocol, or experimental design. Viewers
don’t actually want to read about the gruesome
details, however fascinating you might find
them.
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Key
= Purple Paint Mark
= Cell in nest
Introduction – Polistes wasps
Acknowledgments
Conclusions
References
We hypothesize: If larval removal is
dependent on quality/quantity of food
available, both species should be
equally as likely to remove larvae.
Alternatively, If larval removal is
dependent on other factors (e.g., rates of
parasitism), then species may vary in
removal rates.
Figure 3. Nest mapping number
system. Marks were placed on the
1st, 2nd, 8th, 20th, 38th, and 62nd cell
to assist in nest-mapping.
For further information
Larval removal in paper wasps
Ron Schuck, Dr. Jenny Jandt, and Dr. Amy Toth
Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa 50011
Polistes wasps (also known as ‘paper wasps’) often build their nest
under the eaves of buildings. There are two species common in Ames,
IA – Polistes fuscatus and Polistes metricus (Figure 1). In the process
of monitoring wasp colony development for a larger study, we tracked
the appearance and disappearance of wasp brood– eggs, larvae, and
pupae -- in these two species of paper wasps. Larval removal can be a
sign of colony stress (e.g. parasites, nutrition; Kudo & Shirai 2012) and
high rates of removal can interfere with researchers' ability to conduct
successful experiments.
Kudo & Shirai, (2012) have shown that Polistes wasp adults
occasionally cannibalize the larvae when resources are scarce.
Therefore, we also ask: Under similar environmental conditions,
how does larval removal vary across the two species?
From June 4th – July 23rd 2012, 30 colonies of P. metricus (Figure 2)
and 14 colonies of P. fuscatus were ‘mapped’ (Figure 3) every 3 days.
All colonies were located at the Iowa 4H Center in Madrid, IA. During
a mapping event, the content of each nest cell (egg, larval instar, or
pupa) were recorded.
Data from 10 nests of each species were analyzed. We averaged the
number of 2nd - 3rd instar and 4th - 5th instar larvae that were removed,
and compared data across, species, date, and temperature.
Figure 8. Polistes metricus carrying a 5th instar
larva out of the nest.
Figure 6 shows a 3rd instar larva in a P. metricus nest. There was no evidence that P. fuscatus or P. metricus removed
different numbers of 2nd-3rd instar larvae (ANOVA, p = 0.13), nor that there were different numbers of larvae removed
each day (repeated measures ANOVA, p = 0.09), or that larval removal depended on temperature (ANOVA, p = 0.60).
Data are represented in Figure 4.
Figure 7 shows 5th instar larvae in a P. metricus nest. One adult P. metricus was
observed physically removing a 5th instar larva from the nest (Figure 8).
There was no evidence that P. fuscatus or P. metricus removed different
numbers of 4th-5th instar larvae (ANOVA, p = 0.32). However, the number of 4th-
5th instar larvae removed did differ each day (repeated measures ANOVA, p =
0.04), although this difference was not due to temperature differences (ANOVA,
p = 0.23). Data are represented in Figure 5.
1. No difference between species.
From our data, there was no difference in larval removal rates
between Polistes fuscatus and Polistes metricus.
2. Larval removal varied by day.
Figure 5 shows that the number of 5th instar larvae removed was
consistent between species, but differed by day. This supports our
hypothesis: If larval removal is dependent on quality/quantify of
food available, both species should be equally as likely to remove
larvae each day.
3. Larval removal did not correlate with temperature.
Larval removal was not correlated with temperature (see Figs. 4 & 5),
which suggests that other environmental factors (e.g., humidity, days
since previous rainfall, resources available) may play a role.
4. Other factors that could affect larval removal
We occasionally observed parasites in our nests
(Figure 9). It is possible, that parasitism or disease
may affected an adult’s decision to remove larvae,
and that larval removal was not always due to adults
cannibalizing them to compensate for missing
resources. Future research may address the
question: Does parasitism or disease affect larval
removal rates, and does parasitism and/or disease
rate vary by species?
5. Future directions
An important next step will be to analyze the developmental rates of
larvae in the two species to determine if there is a difference. If
developmental rates, and other stressors vary by species, this
information will be very valuable to researchers investigating paper
wasps.
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ve la
rvae
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D)
mis
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Figure 4. Missing instars 2-3
P. fuscatus
P. metricus
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Ave
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±SD
) m
issi
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Day
Figure 5. Missing instars 4-5
P. fuscatus
P. metricus
Figure 2. A Polistes nest. Cellls
with white caps contain pupae,
other cells contain larvae at various
points of development.
Figure 1. Polistes metricus
Figure 7. Polistes metricus standing on the
nest next to a pupa and 5th instar larva.
Figure 6. The orange arrow points to a third
instar larvae inside a P. metricus nest.
Figure 9. A parasitoid
of paper wasps visiting
a nest in the field.
Kudo,K., and Shirai, A. 2012. Effect of food availability on larval cannibalism by foundresses of
the paper wasp Polistes chinensis antennalis. Insect Sociaux 59:279-84
Many thanks to Dr. Jenny Jandt (EEOB), Dr. Amy Toth (EEOB); all of the Toth Lab members; Dr.
Jonathen Wendel; Ecology, Evolution, and Organismal Biology department at Iowa State
University; and The National Science Foundation.
Please contact Ron Schuck
Ames High School
1921 Ames High Drive,
Ames, IA 50010.