Episimus Life Tables
Overview
The Episimis Life Table project is a project I assist with in Dr. Mark Wright's lab in UH Manoa's College of Tropical Agriculture and Human Resources (CTAHR) working under Michelle Au. The Episimus utilis moth was introduced to Hawaii in 1954 as a biological control agent against the invasive Christmas berry plant (Schinus terebinthifolia), both which originate from Brazil. Christmas berry is an aggressive invader in Hawaii’s ecosystems, outcompeting native vegetation and altering natural landscapes. Initially, Episimus utilis was successful in controlling the spread of this plant; however, in recent years, its effectiveness has declined. Understanding the reasons behind this decline is critical for improving the biocontrol strategy and ensuring that the moth remains a viable tool for managing Christmas berry populations. Our research focuses on raising and maintaining a lab colony of Episimus utilis while also conducting field studies to assess its continued biocontrol viability. By combining laboratory and field experiments, we aim to determine why the moth’s effectiveness is decreasing—likely due to predation or parasitization—and explore ways to enhance its success as a biocontrol agent.
My Role
I play a role in both the laboratory and field components of this study. In the lab, I assist with the rearing of the moth population, ensuring the survival of caterpillars through all five instars and monitoring their transition to pupae and adults.
Beyond the lab, I assist in field experiments where we deposit Episimus caterpillars of different instars onto Christmas berry plants in natural environments. By monitoring survival rates, we assess how effectively the caterpillars suppress the invasive plant. These experiments also allow us to investigate why biocontrol effectiveness has declined. We suspect that predation and parasitization are major factors, so we document any signs of caterpillar loss, potential predators, and parasitoid activity in different locations. By comparing survival rates across multiple field sites, we hope to identify patterns in environmental pressures that could explain reduced effectiveness. I track life history data, including instar mortality rates, pupation success, and adult emergence, constructing life tables to quantify survival at each stage on the Christmas Berry plants in our field experiments. These controlled observations help establish a baseline for understanding the moth’s life cycle and how environmental factors may be affecting its population dynamics and as a result, how they may be affecting the moth’s viability as a biocontrol agent to the invasive plant. Understanding these factors is crucial for improving biocontrol strategies, whether by modifying release methods, identifying more favorable locations for caterpillar introduction, or supplementing the population with laboratory-reared individuals.
What Have I Learned so Far?
This research has significantly strengthened my laboratory, field, and data analysis skills, making use of both my background in biology and computer science. In the lab, I have gained hands-on experience in rearing insect colonies, closely monitoring caterpillars through each instar and ensuring their successful development. I have improved my ability to handle live specimens while also refining my skills in microscopy and insect identification. The fieldwork component has allowed me to apply ecological research techniques, including direct insect releases, population monitoring, and environmental assessments. In addition to laboratory and fieldwork, I utilize data analysis techniques to process and interpret our findings. Using Python, R, and Excel, I analyze life table data, survival rates, and reproductive success, generating statistical models to understand population trends. Integrating biological research with computational methods has reinforced my ability to manage and analyze ecological data, a skill set that is increasingly valuable in conservation science. As this project progresses farther, I will include examples of code I used to assist me in this process.
Future Plans
Moving forward, our research will focus on determining how to increase the effectiveness of the Episimus moth as a biocontrol agent to Christmas Berry trees. We can possibly do this by optimizing release strategies to increase survival rates or investigating potential solutions to counteract predation and parasitization. Ultimately, our goal is to refine biocontrol practices to enhance the long-term suppression of Christmas berry while ensuring ecological safety. By improving our understanding of Episimus utilis and its interactions with Hawaii’s environment, we contribute to more sustainable invasive species management that protects native ecosystems.