In a Tortoiseshell
This is an excerpt from my final paper for EEB329: Sensory Ecology. Students were prompted to design a “dream research project” related to sensory ecology and write a mock scientific research paper complete with abstract, body text, and figures. Inspired by a sighting from my freshman year, I decided to invent a study on green lacewing larvae, juvenile insects that carry miscellaneous debris on their backs.
Excerpt
Decorating is a widespread behavioral strategy in which organisms accumulate and retain exogenous materials such as shells, rock, algae, and carcasses on their exterior (Ruxton & Stevens, 2015; Tauber et al., 2014). The behavior appears among both aquatic and terrestrial taxa, prompting a plethora of hypotheses regarding its adaptive purpose (Ruxton & Stevens, 2015). In some cases, these decorations may serve as a form of masquerade, a camouflage tactic in which organisms resemble innocuous objects to prevent recognition by a potential predator or prey (Ruxton & Stevens, 2015; Skelhorn et al., 2010). Alternatively, organisms may use decoration to blend into the environment and avoid detection, a tactic called background matching (Ruxton & Stevens, 2015). Still other studies have found that chemical rather than visual manipulation affects the efficacy of the decorative shield (Ruxton & Stevens, 2015). Better understanding the evolutionary origins and adaptive value of this behavior would provide insight into the sensory tactics organisms use to fool predators and prey.
While decorating has been well-studied in charismatic species such as the decorator crab, its application to insect larvae attracts less attention in modern ecology research (Ruxton & Stevens, 2015; Tauber et al., 2014). In this study, we examined decorating behavior in the insect family Chrysopidae, commonly known as green lacewings. More than half of the species in this family adopt the practice of decoration to conceal themselves from predators, cannibalistic conspecifics, and unsuspecting prey (Anderson et al., 2003; Mochizuki et al., 2006; Tauber et al., 2014).
Within the family, larvae adopt a variety of decoration tactics. Some are specialists, such as Chrysopa slossonae, which preys on the woolly alder aphid and disguises itself by covering itself with the waxy “wool” secreted by the aphids (Eisner et al., 1978). Some species exhibit phenotypic plasticity; Chrysopa quadripunctata, while typically naked, can adopt the wax disguise of the wooly alder aphid just as well as C. slossonae (Milbrath et al., 1993, 1994). Other more generalist larvae simply cover themselves with an assortment of decorations, including plant particles, spider’s webs, lichen, insect parts, fungal spores, and even live snails (Fig. 1; Appendix Fig. A) (Melo et al., 2024; Smith, 1922; Tauber et al., 2014). The diversity of environmental debris used to construct this decorative “trash packet” has prompted the term “trash-carrying” to refer to Chrysopid larvae decorating behavior (Ruxton & Stevens, 2015).
By conducting predation trials of trash-carrying and artificially denuded larvae, past studies have shown that trash-carrying decreases predation (Anderson et al., 2003; Eisner et al., 1978; Ruxton & Stevens, 2015). However, no studies to date have addressed the gradations in trash packet size beyond the binary categories of “trash-carrying” and “denuded.” Moreover, the particular mechanisms of this anti-predator defense are not well understood. Researchers have hypothesized that trash packets might provide background matching or visual masquerade; physical protection by preventing predator mouthparts from reaching larvae; or chemical protection by signaling unpalatability (Anderson et al., 2003; Melo et al., 2024; Pérez-de La Fuente et al., 2012; Ruxton & Stevens, 2015).
This study investigated the components of visual and physical protection in the trash-carrying larvae of a specialist Chrysopid, Cereaochrysa lineaticornis. Larvae of this species construct their trash packets exclusively from trichomes on the undersides of sycamore tree leaves, taking on the appearance of “tiny ambulatory cotton wads” (Appendix Fig. B, Appendix Fig. C) (Eisner et al., 2002). Unlike other trash packets, the fluffy white trichome disguise of C. lineaticornis provides minimal background matching to sycamore trees; multiple researchers have called it “conspicuous” against the green leaves (Eisner et al., 2002; Smith, 1922; Tauber et al., 2014). The trichome arrangement also does not masquerade as a naturally-occurring object in the environment. This suggests that, contrary to expectation, the decorative trash packet of C. lineaticornis might have an adaptive function beyond visual masquerade and background matching. Past studies have recorded but not quantified instances of attempted attack on trash-carrying C. lineaticornis larvae by reduviid bugs, which were blocked by the trichome trash packet (Eisner et al., 2002). This observation points to physical protection, dependent on trash packet size, as the primary anti-predator mechanism of the C. lineaticornis trash-carrying behavior.
To investigate this, we first tested the ideal trash packet size preferred by larvae by presenting groups of denuded C. lineaticornis larvae with increasing quantities of trichomes. After a reloading period, we then measured the mass of the trash packets the larvae constructed. To assess the effectiveness of these trash packets as physical protection, the larvae were then exposed to predation by reduviid bug nymphs (Pselliopus latispina). From this, we evaluated predation probabilities across larvae with differing trash packet sizes.
In a second experiment to isolate and evaluate the visual effects of the trash packet, we provided groups of denuded larvae with trichomes stained different colors. We then repeated predation trials with these colorfully-adorned larvae to determine if the cryptic appearance of the trash packets was significant to anti-predator defense.
We hypothesized that physical protection would be the most significant component of the anti-predator defense mechanism. Based on this, we expected that increasing trash packet size, measured by mass, would correspond with the lowest predation rates and that color of trichomes in the trash packet would have no significant effect on anti-predator defense.
Bibliography
Anderson, K. L., Seymour, J. E., & Rowe, R. (2003). Influence of a dorsal trash‐package on interactions between larvae of Mallada signata (Schneider) (Neuroptera: Chrysopidae). Australian Journal of Entomology, 42(4), 363—366. https://doi.org/10.1046/j.1440-6055.2003.00373.x
Eisner, T., Carrel, J. E., Tassel, E. V., Hoebeke, E. R., & Eisner, M. (2002). Construction of a defensive trash packet from sycamore leaf trichomes by a Chrysopid larvae (Neuroptera: Chrysopidae). Proceedings of the Entomological Society of Washington, 102(2), 437—446.
Eisner, T., Hicks, K., Eisner, M., & Robson, D. S. (1978). “Wolf-in-Sheep’s-Clothing” Strategy of a Predaceous Insect Larva. Science, 199(4330), 790—794. https://doi.org/10.1126/science.199.4330.790
Melo, T. F. D. O. R., Dos Reis, J. B. A., Pujol-Luz, J. R., De Souza Queiroz Júnior, C., Pinho, D. B., & Schirmer, S. C. (2024). Revealing a new possible camouflage strategy: Use of fungal spores in the “trash package” of Chrysopidae larvae. Symbiosis, 94(1), 65—70. https://doi.org/10.1007/s13199-024-01014-1
Milbrath, L. R., Tauber, M. J., & Tauber, C. A. (1993). Prey Specificity in Chrysopa: An Interspecific Comparison of Larval Feeding and Defensive Behavior. Ecology, 74(5), 1384—1393. https://doi.org/10.2307/1940068
Milbrath, L. R., Tauber, M. J., & Tauber, C. A. (1994). Larval behavior of predacious sister-species: Orientation, molting site, and survival in Chrysopa. Behavioral Ecology and Sociobiology, 35, 85—90.
Mochizuki, A., Naka, H., Hamasaki, K., & Mitsunaga, T. (2006). Larval Cannibalism and Intraguild Predation Between the Introduced Green Lacewing, Chrysoperla carnea, and the Indigenous Trash- Carrying Green Lacewing, Mallada desjardinsi (Neuroptera: Chrysopidae), as a Case Study of Potential Nontarget Effect Assessment. Environmental Entomology, 35(5), 1298—1303.
Pérez-de La Fuente, R., Delclòs, X., Peñalver, E., Speranza, M., Wierzchos, J., Ascaso, C., & Engel, M. S. (2012). Early evolution and ecology of camouflage in insects. Proceedings of the National Academy of Sciences, 109(52), 21414—21419. https://doi.org/10.1073/pnas.1213775110
Ruxton, G. D., & Stevens, M. (2015). The evolutionary ecology of decorating behaviour. Biology Letters, 11(6), 20150325. https://doi.org/10.1098/rsbl.2015.0325
Author Commentary / Jessica Wang
I initially chose to research Chrysopid larvae because I thought they were amusing. These little insects walk around looking like clumps of lichen, dirt, and fluff for protection, and I wanted to learn more. Beyond my personal motive, however, I found that there was a real mystery in existing research about the way these larvae collected and used their so-called trash packets.
The Writing Center lexicon helped me refine this into my scholarly motive: in my case, a scientific puzzle or mystery with conflicting published hypotheses. Why do the larvae carry trash packets? What function do they serve? How exactly do they prevent predation? In the words of the Motivating Moves handout, “We can learn about a larger phenomenon by studying this smaller one.”
We’re often taught to recognize and apply concepts like orienting, literature review, and motive in the context of humanities literature, but I’ve found that I can identify the same components in scientific research papers if I look closely enough. They’re often embedded in the Abstract or Introduction, with signposting phrases like “poorly understood,” “remains uncertain,” or “little is known about….” With these words, researchers set up an open or unanswered question—the gap in past research that justifies their study.
It is this phrasing and style that I tried to mimic in the introduction of my paper. While I begin by orienting the reader to decorating behavior and the Chrysopidae family, I also frame the limitations and gaps in existing research. I hope that this example helps students identify and develop scholarly motive in their own and others’ scientific research papers.
Editor Commentary / Cindy Lei
What is the relationship between research and writing?
Everyone at Princeton is required to complete some form of ”research” or “original work” as a part of the curriculum. For some fields, particularly in STEM, it can be easy to believe that the “research” is separate from reading literature or writing the actual paper. As a counterexample, I put forward this excellent introduction from Jessica’s imagined study on Chrysopidae larvae. Shockingly, this was purely a writing exercise, with no actual experiment run. Jessica shows us in a tangible way how principles of writing can be applied to design a research project, and then to communicate its scientific significance.
A good place to start is always motive. Jessica masterfully layers motives, taking us from the broad to the narrow, and back again. We first start with the key term decorating, “a widespread behavioral strategy” used by many organisms, and are quickly shown how much, and then how little, we know about it. Jessica invokes two major gaps in the scientific literature: most decorating strategies are assumed to function visually, and less charismatic species such as insects are understudied. Essentially, Jessica is saying that there is a lot that we don’t know about deceptive/defensive sensory tactics used in nature.
Alright, we have a potential scientific impact in the form of a scholarly motive. But how do we accomplish this? Jessica then introduces us to her textual motive—the existence of this little bug that paradoxically wears a coat of white fluff while living on a green leaf. This textual motive put together with the scholarly motive forms a research aim/goal, but it also motivates the methodologies (how to collect evidence and how to analyze it) and primary sources (what data to collect) to be employed. If we are curious about the mismatch in the color, it makes sense to do an experiment where we change the color of the bug’s fluff. And if we wonder what the point of the fluff is, it makes sense to measure something like larvae survival rate.
In a way, the introduction for a scientific study is often a miniature essay: it is an argument for the hypothesis. An invitation to make a wager on something small (whether the larvae will be eaten) that has much larger implications for the field (perhaps we ought to re-examine other instances of decorating and investigate how exactly it helps the organism). This is a paper that would bring value to more than just the bug specialists. Even better, thoughtful orienting is interspersed throughout that allows non-specialists to follow along, supporting the other elements of the paper.
If we see writing as more than just the act of putting pen to paper, but also an active process of organizing thought and communicating, then research must begin and end with writing. Writing is how we formulate the questions we seek to answer in our research, as well as how we interpret the answers we find.
You must be logged in to post a comment.