Catching Invasive Flies in the Galapagos Islands

June 18, 2019

By Andrea Cahuana, Research Assistant on the Philornis downsi Project at the Charles Darwin Foundation

To catch flies! I still remember the first day I arrived at the Charles Darwin Research Station in March 2014 to interview as a local entomology volunteer and saw hundreds of flies inside cages. My legs wobbled and I thought, “what have I gotten into”?! Piedad Lincango, the researcher in charge of the Philornis downsi laboratory at the time, explained to me why these introduced flies were being studied and the deadly effects of their blood-feeding larvae on the hatchlings of many of the small landbirds that are unique to the Galapagos Islands.

Andrea Cahuana inspecting fly traps.

A sharp eye is needed to identify ‘P. downsi’ in traps as they are very similar to other flies found in Galapagos–it is all about the wing venation! (© CDF)

As a young Galapagueña student in my first year studying ecotourism at the Galapagos campus of the Central University of Ecuador, and with no background in biology or entomology, I asked myself “how could I possibly help?”. So great was my curiosity to learn about everything they did inside the laboratory — and so tempting the opportunity to contribute — that I accepted the volunteer position. I entered a world where science for conservation is the primary focus of everything we do. As a member of the project, I have had the opportunity to meet local, national, and foreign professionals with different cultures, customs, and languages — all enthusiastically sharing their knowledge and experiences.

Andrea Cahuana hanging fly traps.

Up to 150 traps are hung in trees every week to catch the invasive fly, ‘P. downsi’ for use in research. (© CDF)

My first job as a volunteer was to organize the weekly activities for the ongoing monitoring of P. downsi populations in the wild, in order to understand the patterns of this fly in relation to climate and the availability of its bird hosts. Each week, we hang up to 150 traps baited with papaya juice in trees to capture the greatest number of live flies possible. These traps are checked twice daily, and the trapping is done year-round with the help of a group of volunteers. Each fly caught is taken to the laboratory for subsequent research, either to understand their reproductive biology or to evaluate different control techniques. Live flies are also sent to the USA so that our collaborating scientists can continue their work and we can progress more rapidly.

In 2015, I was offered the opportunity to work as a research assistant within the project, and I committed to work with the team to search for a solution to combat this harmful fly. I started working very closely with collaborating scientists who are studying possible attractants in the hope of finding the most promising one for use in a large-scale fly trapping program in the nesting areas of endangered land birds. I also help with research to develop methods to rear P. downsi in captivity. The latter is a very delicate process, and requires patience and considerable time and care to ensure that the flies complete their life cycle. In the wild, the larvae of this fly feed on the blood of baby birds, and there are many challenges to recreate these conditions in the laboratory.

For five years now, I have been part of this hard-working team that invests time and passion into their work — with the sole purpose of finding a solution to save Galapagos landbirds from this parasitic fly. Of all my personal and professional experiences, this one is the most rewarding — being part of a team dedicated to the conservation of the fauna of the Galapagos Islands.

Andrea and Magally Infante checked fly traps every dear.

Rain or shine, fly traps are checked every day by Andrea and local volunteer Magally Infante. (© CDF)

Andrea Cahuana Andrea Cahuana is a young Galapagueña who graduated from the Central University of Ecuador, Galapagos, in Ecotourism. She has been working since 2014 on the Philornis downsi Project, first as a volunteer and currently as a research assistant.

Galapagos Conservancy has been supporting the Charles Darwin Foundation’s Landbird project since 2013. Read more about the conservation of landbirds in Galapagos.

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