Statistical Analysis
To analyze these data, I used binomial generalized linear models with a
with a complementary log-log link function in R (ver. 1.1.463). For all
models, I set avian predation as the binomial response variable (0 = not
attacked, 1 = attacked) and included days exposed as an offset term. For
the primary model, I included the following independent variables:
trial, location, leaf roll treatment (rolled, open), color treatment
(eyespotted, non-eyespotted), canopy openness (a proportion, from 0 =
sky fully obscured to 1 = sky not obscured by anything), and plant
height (in cm). I also tested for an interaction between the roll
treatment and color treatment. To determine the statistical significance
of each independent variable across the model, I compared the full model
to models lacking the term of interest using likelihood ratio tests
(package lmtest). To determine the simple effects of eyespots and leaf
rolls, without the interaction effect, I constructed 4 additional models
using data from (1) only eyespotted prey, (2) only non-eyespotted prey,
(3) only leaf-rolled prey, and (4) only open-leaf prey. For models (1)
and (2), I compared full models to models without the leaf roll
treatment; for models (3) and (4), I compared full models to models
without the color treatment. These comparisons were also made using
likelihood ratio tests.
RESULTS
The overall avian predation rate was 13.4% of artificial caterpillars
over a 5-day period. Predation did not vary significantly by trial
(χ2 = 0.79, df = 1, p = 0.38), location
(χ2 = 0.55, df = 1, p = 0.46), canopy openness
(χ2 < 0.01, df = 1, p = 0.95), or
plant size (χ2 = 0.71, df = 1, p = 0.40). Leaf
rolls significantly reduced predation relative to prey on open leaves
(12.9% reduction, χ2 = 24.43, df = 1, p
< 0.001). This was true of both eyespotted (17.3% reduction,
χ2 = 25.77, df = 1, p < 0.001) and
non-eyespotted (8.4% reduction, χ2 = 4.54, df= 1, p < 0.05) prey. Eyespots alone had no significant effect
on predation (χ2 = 0.91, df = 1, p = 0.34),
though this was only true for prey on open leaves (χ2= 0.13, df = 1, p = 0.72). There was a significant interaction
between leaf rolls and eyespots (χ2 = 5.96, df= 1, p < 0.05): in leaf rolls, eyespots reduced the
probability of predation (7.1% reduction, χ2 = 6.98,df = 1, p < 0.01).
DISCUSSION
In this study, leaf rolls not only protected prey in general, but also
increased the effectiveness of eyespots at deterring visual predators
(Fig. 2). This result supports the environmental deimatism hypothesis,
i.e., the active use of objects in the environment to create a deimatic
display. Similar to the mounds built by bowerbirds for sexual
communication (Endler et al. 2010), leaf rolls are not just
passive “backgrounds,” but an integral part of the visual signal’s
success. While environmental modification has been shown to effectively
complement (or serve as) visual camouflage in several systems (Canfield
2009; Hultgren & Stachowicz 2011), these behaviors are not
well-documented in other types of visual defense (e.g. aposematism,
mimicry, masquerade, deimatism). Environmental deimatism may be a common
strategy among other leaf-sheltering organisms, such as eyespotted
hesperiid caterpillars (Janzen 2010) or spiders that abruptly jump out
of rolls when disturbed (Postema pers. observations, Fig. 3).
Beyond leaf rolls, environmental deimatism may exist as a more general
strategy for shelter-using or -building species.
The overall protective effect of leaf rolls supports past experimental
work on these structures’ role in predator defense (Murakami 1999;
Tvardikova & Novotny 2012). However, the mechanism of protection is not
entirely clear. One possibility is that leaf rolls physically hide the
organism from detection. However, folded leaves are relatively
noticeable against non-folded foliage; in some systems, leaf rolls even
seem to act as a target for visually-oriented predators (Kobayashiet al. 2020). Naturally occurring leaf rolls in the study area
were common, and often occupied by living organisms: over half (56%) of
surveyed plants had at least one leaf roll, and over a third (34%) of
rolls were occupied. Given their frequency and apparent profitability,
it seems advantageous for avian predators to learn to search for prey in
leaf rolls. However, the organisms inhabiting leaf rolls were not
necessarily desirable prey items (Fig. 3). Surveyed rolls most commonly
contained small, fast-moving spiders (49% of occupied rolls). Spiders
often jumped from the roll immediately when disturbed, potentially
making prey startling, hard to catch, or both. Other common prey items
included very small organisms (e.g. springtails) and small weevils that
often dropped to the ground when disturbed. Larger, less mobile, and
more profitable prey – e.g. caterpillars – were rare (found in only
~4% of occupied rolls). The main defensive function of
the leaf roll, then, may be to conceal prey identity. The added
ambiguity and handling time of leaf rolls may make them relatively
low-value foraging microhabitats, though this likely depends on the
predator community’s degree of specialization, and perhaps temporal
shifts in leaf roll abundance/occupancy. Predator uncertainty could
further enhance the effectiveness of unexpected or startling visual
signals as well.
Eyespots did not significantly increase predation risk on open leaves
relative to non-eyespotted prey on open leaves (Fig. 2). This could
suggest that prey with large eyespots are not more detectable to visual
predators than prey without eyespots. Given that birds are highly
attuned to eye-like stimuli, this seems unlikely (De Bona et al.2015). Alternatively, readily visible eyespots may be more detectable to
predators, but simultaneously function to deter predators at a distance.
In this scenario, the combined effects of eyespots (increased detection
and predator deterrence) may be counterbalanced. This hypothesis is
supported by the fact that the majority of Papilio species that
possess eyespots rest on open leaves, as well as the general positive
association between body size and presence of eyespots in lepidopteran
larvae (Wagner 2005; Hossie et al. 2015; Gaitonde et al.2018). The fear of paired, eye-like patterns appears to be relatively
innate for avian predators (Merilaita et al. 2011). This
contrasts with other conspicuous color strategies, such as aposematism,
where learning is more central to the pattern’s antipredator effect
(Hämäläinen et al. 2020). If eye mimicry does not require
predators to have prior negative experience with the “model” organism,
then costs of being conspicuous due to encounters with naïve predators
may be minimal.
Habitat characteristics may have also played a role in the perception
and effectiveness of eyespots in this study. Both field sites were
densely vegetated, with an average canopy openness of 14.3% (SD: 8.3%)
– i.e, ~86% of the area above each artificial
caterpillar was covered by vegetation. In complex, highly vegetated, and
low-light environments, it may be difficult for predators to distinguish
between real and fake eyes, or it may be too risky to spend a long time
investigating (Janzen et al. 2010). This may also help to explain
why eyespots did not significantly increase predation, despite
presumably higher predator detection, compared to non-eyespotted prey on
open leaves (Fig. 2). While there was no direct support for the
influence of background conditions (such as canopy openness and plant
height) on avian predation in this study, I did not experimentally
manipulate these characteristics. In other studies of visual signalling,
habitat heterogeneity, vegetation density, and lighting conditions have
had effects on the perception of animal color patterns (Gotceitas &
Colgan 1989; Endler 1993; Coker et al. 2009; Seymoure et
al. 2018). To better understand the effect of environmental context on
the perception of eyespots, it would be useful to directly observe
predator responses to eyespotted and non-eyespotted prey across various
habitat types.
It may be useful to consider P. troilus leaf rolls as an example
of Dawkin’s “extended phenotype” (1999). There are clear consequences
of the leaf roll on caterpillar fitness, as well as synergistic
interactions between leaf rolling and color traits (Fig. 2). In this
system, selection is acting on multiple interacting levels: on the
structure of the roll, the expression of leaf-rolling behavior, and the
organism’s color patterns (Laland 2004; Hunter 2018). This makes the
evolution of environmental deimatism a question of both morphology and
behavior. Umbers et al (2017) suggest two potential pathways for how
deimatic displays evolve: the “defense-first” and “startle-first”
hypotheses. In the former, initially cryptic prey gain constitutive
defenses (e.g., toxins), which then selects for conspicuous color
patterns to advertise toxicity, and finally a concealing mechanism to
create the “startle” effect. In the latter, initially cryptic prey
develop a sudden movement that deters predators, which is later enhanced
by a conspicuous visual component (and additional chemical defenses, in
some species). Given that P. troilus larvae are generally
considered non-toxic (Wagner 2005), the “startle-first” hypothesis may
be more likely. Via this pathway, we would expect larvae to have evolved
the leaf-rolling behavior (a proxy for the “sudden movement”) before
the development of large, conspicuous eyespots. It is less likely that
leaf-rolling developed simply as a way to conceal conspicuous eyespots,
as there were no obvious detectability costs of eyespots for prey on
open leaves (Fig. 2). This aligns with Schaedlin and Taborsky’s (2009)
observation that external structures involved in signalling often
provide an initial, direct fitness benefit to the signaler, that then
selects for a progressively stronger signal. A phylogenetic comparative
study, tracking both color traits and deimatic behaviors across the
evolutionary history of swallowtails and/or other relevant lepidopteran
groups, could potentially clarify when and how the behavior-morphology
pairing arose (Janzen et al. 2010; Vidal-García et al.2020).
Given that leaf-rolling is an effective antipredator strategy forP. troilus larvae, and appears to work synergistically with the
species’ defensive color strategy (Fig. 2), why is leaf-rolling not
observed more generally across swallowtails? One possible constraint is
the time and energy investment involved in constructing multiple leaf
rolls over the course of larval development. After larvae lay down
layers of silk, leaves may take over an hour to fully fold into a roll
(supplemental video 1). These periods of high activity and potential
exposure to predators are not accounted for in this study, but may
temper the antipredator benefit of leaf rolls. Secondly, some host
plants may not be conducive to the formation of leaf rolls. The leaves
of common P. troilus host plants are relatively thin, wide, and
flexible compared to common host plants of other eyespotted swallowtail
species (e.g., Populus spp., Salix spp.; Wagner 2005).
While many Papilio larvae form Velcro-like silk pads to rest on,
the leaves of their host plants may be too stiff, thick, or narrow to
easily fold into full leaf rolls. Larvae in the swallowtail family
(Papilionidae) use a diverse array of host plants, and their
later-instar color defenses correspond closely to evolutionary shifts in
host plant usage – e.g., aposematism has mainly evolved in larvae that
use narrow-leafed, toxic plants, while cryptic or mimetic strategies are
associated with more dense, nontoxic plants (Gaitonde et al. 2018). It
would be worth investigating how other aspects of host plant morphology
(particularly leaf width and thickness) may have shaped the evolution of
leaf-rolling, deimatism, and color traits among insects (Janzen et
al. 2010).
The results of this study provide support for the environmental
deimatism hypothesis, and, more generally, the key role of behavior in
defensive visual signals (Ruxton et al. 2009; Cuthill et
al. 2017; Stevens & Ruxton 2018). They also suggest that deimatic
displays can arise without strong costs to conspicuousness, though this
likely depends on the mechanism of predator deterrence (learned vs.
reflexive avoidance). To better understand the ecology and evolution of
defensive visual signals, it is essential to consider color patterns
less as static characters, and more as “multivariate optima”; i.e.,
complex strategies that may involve selection on morphology, behavior,
and/or extended phenotypes beyond the body of the organism (Dawkins
1999, Laland 2004, Cuthill et al. 2017, Stuart-Fox 2022, Postema et al.
2022).
ACKNOWLEDGEMENTS
Thank you to Louie Yang, Andy Sih, and Rick Karban for their assistance
in developing the experimental design. Additional thanks to Hee Jin
Chung, Gwen Erdosh, Kirsten Sheehy, and Lohit Garikpati for help with
constructing clay caterpillars; to Louie Yang and Tracie Hayes for
comments on the manuscript; and to Pavel G. for his assistance with
fieldwork. Caterpillar molds were designed and printed with the help of
Tez Stair and Steven Lucero. Caterpillar icons were created by Mia
Lippey. Spectral measurements were taken thanks to Alison Rabosky and
Hayley Crowell. All study sites were used with permission from the Ann
Arbor Parks and Recreation Department and the University of Michigan.
FUNDING INFORMATION
This project was funded by the Phi Beta Kappa Northern California
Association graduate scholarship, UC Davis Jastro-Shields graduate
research award, and NSF IntBIO Collaborative Research grant
(IOS-2128245).
REFERENCES
Aronsson, M. & Gamberale-Stille, G. (2009). Importance of internal
pattern contrast and contrast against the background in aposematic
signals. Behav Ecol , 20, 1356–1362.
Badiane, A., Carazo, P., Price-Rees, S.J., Ferrando-Bernal, M. &
Whiting, M.J. (2018). Why blue tongue? A potential UV-based deimatic
display in a lizard. Behav Ecol Sociobiol , 72, 1-11.
Barnett, J.B., Cuthill, I.C. & Scott-Samuel, N.E. (2018).
Distance-dependent aposematism and camouflage in the cinnabar moth
caterpillar (Tyria jacobaeae , Erebidae). R Soc Open Sci ,
5, 171396.
Barnett, J.B., Redfern, A.S., Bhattacharyya-Dickson, R., Clifton, O.,
Courty, T., Ho, T., et al. (2017). Stripes for warning and
stripes for hiding: spatial frequency and detection distance.Behav Ecol , 28, 373–381.
Blake, J.G., & Hoppes, W.G. (1986). Influence of resource abundance on
use of tree-fall gaps by
birds in an isolated woodlot. Auk, 103, 328-340.
Canfield, M.R. (2009). The double cloak of invisibility: phenotypic
plasticity and larval decoration in a geometrid moth, Synchlora
frondaria , across three diet treatments. Ecol Entomol , 34,
412–414.
Caro, T. & Allen, W.L. (2017). Interspecific visual signalling in
animals and plants: a functional classification. Philos Trans R
Soc Lond B Biol Sci , 372, 20160344.
Coker, D.J., Pratchett, M.S. & Munday, P.L. (2009). Coral bleaching and
habitat degradation increase susceptibility to predation for
coral-dwelling fishes. Behav Ecol , 20, 1204–1210.
Cuthill, I.C., Allen, W.L., Arbuckle, K., Caspers, B., Chaplin, G.,
Hauber, M.E., et al. (2017). The biology of color.Science , 357, eaan0221.
Dawkins, R. (1999). The Extended Phenotype: The Long Reach of the
Gene . Revised edition. Oxford University Press, Oxford, UK.
De Bona, S., Valkonen, J.K., López-Sepulcre, A. & Mappes, J. (2015).
Predator mimicry, not conspicuousness, explains the efficacy of
butterfly eyespots. Proc Royal Soc B , 282, 20150202.
Dookie, A.L., Young, C.A., Lamothe, G., Schoenle, L.A. & Yack, J.E.
(2017). Why do caterpillars whistle at birds? Insect defence sounds
startle avian predators. Behav Processes , 138, 58–66.
Drinkwater, E., Allen, W.L., Endler, J.A., Hanlon, R.T., Holmes, G.,
Homziak, N.T., et al. (2022). A synthesis of deimatic behaviour.Biol Rev , 97, 2237-2267.
Endler, J.A. (1983). Natural and sexual selection on color patterns in
poeciliid fishes. Environ Biol Fish , 9, 173–190.
Endler, J.A. (1993). The color of light in gorests and its implications.Ecol Monogr , 63, 2–27.
Endler, J.A., Endler, L.C. & Doerr, N.R. (2010). Great bowerbirds
create theaters with forced perspective when seen by their Audience.Curr Biol , 20, 1679–1684.
Fabricant, S.A. & Herberstein, M.E. (2015). Hidden in plain orange:
aposematic coloration is cryptic to a colorblind insect predator.Behav Ecol , 26, 38–44.
Gaitonde, N., Joshi, J. & Kunte, K. (2018). Evolution of ontogenetic
change in color defenses of swallowtail butterflies. Ecol Evol ,
8, 9751–9763.
Gotceitas, V. & Colgan, P. (1989). Predator foraging success and
habitat complexity: quantitative test of the threshold hypothesis.Oecologia , 80, 158–166.
Halfwerk, W., Jones, P.L., Taylor, R.C., Ryan, M.J. & Page, R.A.
(2014). Risky ripples allow bats and frogs to eavesdrop on a
multisensory sexual display. Science , 343, 413–416.
Hämäläinen, L., Mappes, J., Rowland, H.M., Teichmann, M. & Thorogood,
R. (2020). Social learning within and across predator species reduces
attacks on novel aposematic prey. J Anim Ecol , 89, 1153–1164.
Hossie, T.J. & Sherratt, T.N. (2012). Eyespots interact with body
colour to protect caterpillar-like prey from avian predators. Anim
Behav , 84, 167–173.
Hossie, T.J. & Sherratt, T.N. (2013). Defensive posture and eyespots
deter avian predators from attacking caterpillar models. Anim
Behav , 86, 383–389.
Hossie, T.J. & Sherratt, T.N. (2014). Does defensive posture increase
mimetic fidelity of caterpillars with eyespots to their putative snake
models? Curr Zool , 60, 76–89.
Hossie, T.J., Sherratt, T.N., Janzen, D.H. & Hallwachs, W. (2013). An
eyespot that “blinks”: an open and shut case of eye mimicry inEumorpha caterpillars (Lepidoptera: Sphingidae). J Nat
Hist , 47, 2915–2926.
Hossie, T.J., Skelhorn, J., Breinholt, J.W., Kawahara, A.Y. & Sherratt,
T.N. (2015). Body size affects the evolution of eyespots in
caterpillars. PNAS , 112, 201415121.
Hultgren, K. & Stachowicz, J. (2011). Camouflage in decorator crabs:
integrating ecological, behavioural and evolutionary approaches. In:Animal Camouflage: Mechanisms and Function , [eds. Stevens, M.,
& S. Merilaita], Cambridge University Press, Cambridge, UK, pp.
212–236.
Hunter, P. (2018). The revival of the extended phenotype. EMBO
Rep , 19, e46477.
Janzen, D.H., Hallwachs, W. & Burns, J.M. (2010). A tropical horde of
counterfeit predator eyes. PNAS , 107, 11659–11665.
Kobayashi, C., Matsuo, K. & Kawata, M. (2020). Contradictory effects of
leaf rolls in a leaf-mining weevil. Sci Rep , 10, 12180.
Kobayashi, C., Matsuo, K., Watanabe, K., Nagata, N., Suzuki-Ohno, Y.,
Kawata, M., et al. (2015). Arms race between leaf rollers and
parasitoids: diversification of plant-manipulation behavior and its
consequences. Ecol Monogr , 85, 253–268.
Laland, K.N. (2004). Extending the extended phenotype. Biol
Philos , 19, 313–325.
Leslie, A.J. & Fleming, N. (1990). Role of the osmeterial gland in
swallowtail larvae (Papilionidae) in defense against an avian predator.J Lepid Soc , 44, 245-251.
de Lira, J.J.P.R., Perez-Jvostov, F., Gotanda, K.M., Kou-Giesbrecht, S.,
Pease, S.K., Jackson, M., et al. (2018). Testing for a
whole-organism trade-off between natural and sexual selection: are the
male guppies preferred by females more likely to be eaten by predators?Evol Ecol Res , 19, 441–453.
Mappes, J., Kokko, H., Ojala, K. & Lindström, L. (2014). Seasonal
changes in predator community switch the direction of selection for prey
defences. Nat Commun , 5, 5016.
Marshall, N.J. (2000). Communication and camouflage with the same
‘bright’ colours in reef fishes. Philos Trans R Soc Lond B Biol
Sci , 355, 1243–1248.
Merilaita, S., Vallin, A., Kodandaramaiah, U., Dimitrova, M., Ruuskanen,
S. & Laaksonen, T. (2011). Number of eyespots and their intimidating
effect on naïve predators in the peacock butterfly. Behav Ecol ,
22, 1326–1331.
Murakami, M. (1999). Effect of avian predation on survival of
leaf-rolling lepidopterous larvae. Pop Ecol , 41, 135–138.
Nyffeler, M., Şekercioğlu, Ç.H. & Whelan, C.J. (2018). Insectivorous
birds consume an estimated 400–500 million tons of prey annually.Sci Nat , 105, 47.
Postema, E.G. (2022). The effectiveness of eyespots and masquerade in
protecting artificial prey across ontogenetic and seasonal shifts.Curr Zool , 68, 451-458.
Postema, E.G., Lippey, M.K. & Armstrong-Ingram, T. (2022). Color under
pressure: how multiple factors shape defensive coloration. Behav
Ecol , XX, 1-13.
Prudic, K.L., Skemp, A.K. & Papaj, D.R. (2007). Aposematic coloration,
luminance contrast, and the benefits of conspicuousness. Behav
Ecol , 18, 41–46.
Richards, L.A, & Coley, P.D. (2008). Combined effects of host plant
quality and predation on a tropical lepidopteran: a comparison between
treefall gaps and the understory in Panama. Biotropica , 40,
736-741.
Romero, G.Q., Gonçalves-Souza, T., Roslin, T., Marquis, R.J., Marino,
N.A.C., Novotny, V., et al. (2022). Climate variability and
aridity modulate the role of leaf shelters for arthropods: A global
experiment. Glob Change Biol, 28, 3694–3710.
Rowe, C. (1999). Receiver psychology and the evolution of multicomponent
signals. Anim Behav , 58, 921–931.
Rowland, H.M., Speed, M.P., Ruxton, G.D., Edmunds, M., Stevens, M. &
Harvey, I.F. (2007). Countershading enhances cryptic protection: an
experiment with wild birds and artificial prey. Anim Behav , 74,
1249–1258.
Ruxton, G.D., Speed, M.P. & Broom, M. (2009). Identifying the
ecological conditions that select for intermediate levels of aposematic
signalling. Evol Ecol , 23, 491–501.
Schaedelin, F.C. & Taborsky, M. (2009). Extended phenotypes as signals.Biol Rev , 84, 293–313.
Seymoure, B.M., Raymundo, A., McGraw, K.J., McMillan, W.O. & Rutowski,
R.L. (2018). Environment-dependent attack rates of cryptic and
aposematic butterflies. Curr Zool , 64, 663–669.
Skelhorn, J., Holmes, G.G., Hossie, T.J. & Sherratt, T.N. (2016a).
Eyespots. Curr Biol , 26, 52–54.
Skelhorn, J., Holmes, G.G. & Rowe, C. (2016b). Deimatic or aposematic?Anim Behav , 113, 1–3.
Stevens, M. & Ruxton, G.D. (2018). The key role of behaviour in animal
camouflage. Biol Rev , 94, 116-134.
Stuart-Fox, D. (2022). Defensive coloration as a multivariate optimum: a
comment on Postema et al. Behav Ecol , arac065.
Stuart-Fox, D. & Moussalli, A. (2008). Selection for social signalling
drives the evolution of chameleon colour change. PLoS Biol, 6,
22–29.
Tan, E., Reid, C., Symonds, M., Jurado-Rivera, J. & Elgar, M. (2017).
The role of life-history and ecology in the evolution of color patterns
in Australian chrysomeline beetles. Front Ecol Evol , 5, 1-15.
Tvardikova, K. & Novotny, V. (2012). Predation on exposed and
leaf-rolling artificial caterpillars in tropical forests of Papua New
Guinea. J Trop Ecol , 28, 331–341.
Umbers, K.D.L., De Bona, S., White, T.E., Lehtonen, J., Mappes, J. &
Endler, J.A. (2017). Deimatism: a neglected component of antipredator
defence. Biol Lett , 13, 20160936.
Umbers, K.D.L., Lehtonen, J. & Mappes, J. (2015). Deimatic displays.Curr Biol , 25, 58–59.
Umbers, K.D.L. & Mappes, J. (2015). Postattack deimatic display in the
mountain katydid, Acripeza reticulata . Anim Behav , 100,
68–73.
Umbers, K.D.L. & Mappes, J. (2016). Towards a tractable working
hypothesis for deimatic displays. Anim Behav , 113, 5–7.
Umbers, K.D.L., White, T.E., De Bona, S., Haff, T., Ryeland, J.,
Drinkwater, E., et al. (2019). The protective value of a
defensive display varies with the experience of wild predators.Sci Rep , 9, 463.
Vidal-García, M., O’Hanlon, J.C., Svenson, G.J. & Umbers, K.D.L.
(2020). The evolution of startle displays: a case study in praying
mantises. Proc R Soc B: Biol Sci, 287, 20201016.
Wagner, D.L. (2005). Caterpillars of Eastern North America: A
Guide to Identification and Natural History . Princeton University
Press, Princeton, N.J.
Whiting, M.J., Noble, D.W.A. & Qi, Y. (2022). A potential deimatic
display revealed in a lizard. Biol J Linn Soc, 136, 455–465.
Figure 1. (a) A live spicebush swallowtail (Papilio
troilus ) larva on sassafras (Sassafras albidum ). Its leaf
roll is held open, with strands of silk visible above the head.
Eyespotted (b) and non-eyespotted (c) artificial larvae on open S.
albidum leaves. (d) A true leaf roll with a live P. troiluslarva inside. (e) An artificial leaf roll with an artificial larva
inside. (f) A live P. troilus larva in a leaf roll, its eyespots
partially visible up-close. Photographs by EGP.
Figure 2. Mean proportions of artificial prey in each leaf roll
treatment group (rolled versus open) attacked by avian predators, ± SE
(n = 659). Yellow points represent eyespotted prey, while green points
represent non-eyespotted prey. Illustrations by Mia Lippey.
Figure 3. (Left) Total counts of each organism type found in
surveys of naturally occurring leaf rolls (n = 464). Within each
organism category, counts of individuals that displayed escape behaviors
in response to the leaf roll being disturbed (dropping, jumping, or no
response) are represented in yellow, red, and brown, respectively.
(Right) Examples of naturally occurring leaf rolls I observed in the
field; leaf rolls varied in size, structure, and plant species.
Photographs and illustrations by EGP.