Results

Methods

Materials and

methods

Be brief, and opt for photographs or drawings

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= 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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Figure 4. Missing instars 2-3

P. fuscatus

P. metricus

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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

ronmarathon@mchsi.com

Ames High School

1921 Ames High Drive,

Ames, IA 50010.