Rearing an Invasive Fly in Galapagos: A Critical Step in its Control

August 18, 2017

By Paola Lahuatte, Junior Researcher in the Philornis downsi project at the Charles Darwin Research Station.

I was so excited when I heard that I had been selected for an internship at the Charles Darwin Research Station (CDRS) to help on a project designed to control the invasive parasitic fly, Philornis downsi, that was having a detrimental impact on Darwin’s finches. The larvae of this introduced fly are ectoparasites of baby birds, and their feeding causes a high percent of hatchlings to die in each nest. This fly is believed to be the main reason for the decline of landbird species in Galapagos — including several that are endangered.

Vermilion Flycatcher in Galapagos

Vermilion flycatcher (© David Anchundia/CDF)

I arrived in the Galapagos Islands in the middle of 2013 after completing my undergraduate classes at the Central University of Ecuador. This was a new area of research for me; on the mainland I had studied ticks and mosquitos. My job was to help figure out how to raise the flies in captivity in the absence of its bird hosts — not an easy task and, to our knowledge, one that had never been achieved for flies that are parasites of birds. However, this study was very necessary. Researchers investigating methods to control P. downsi could only access flies during the bird breeding season (January to May), thus losing out on valuable research time — seven months every year!

Working with flies that need blood to complete their life cycle was quite a challenge. I needed to create a new system specially designed for the larvae — a big responsibility, but the idea of helping the birds fed my spirit. When I first began this work, there were still many gaps in our understanding of the fly’s biology. In the field we easily found it in the birds’ nests, sometimes in very large numbers. It was very successful in completing its life cycle in all types of bird nests, from nests made of sticks in the hot arid zone to nests made of moss in the cool, humid highlands. Yet, in the laboratory it was fragile and its requirements a mystery.

Paoloa in the lab

Paola in the CDRS Philornis lab (© Julio Rodriguez)

The challenge was on. I never gave up thanks to the mentorship of Drs. Piedad Lincango and Charlotte Causton. A few months into the project, I accepted their offer to become a scholarship student and carry out my undergraduate thesis with this project. After a year of perseverance and hard work, I was finally able to develop a simple method for rearing eggs and larvae of P. downsi for the first time inside a laboratory. With this, I successfully completed my thesis and obtained my degree from the Central University of Ecuador.

To learn more about Philornis flies, I wrote to Dr. George Heimpel at the University of Minnesota, lead researcher of a program investigating the possibility of using natural enemies to control P. downsi and a collaborator of the Charles Darwin Research Station. I wanted to learn more about techniques we could use to control this fly. Also, improving my English was at the top of my to-do list. In 2015, I traveled for the first time to the USA, where I encountered a subzero climate, frozen lakes and a white panorama. My adventure was made easier with the warm welcome by my hosts — the Heimpel family. It took a while until I could communicate with people in English, as the learning curve was steep. As I neared the end of my internship, a position became available for a junior researcher in the Philornis Project! I applied and got the job.

Warbler finch nestlings

Warbler finch nestlings in Galapagos (© Paul Schmitz Yanez)

In October of 2015, I returned to work at the Charles Darwin Research Station in Galapagos. The fly continues to have a considerable impact on finches and other birds, and the challenge of finding control methods continues. The international working group that had been created by the Charles Darwin Foundation and the Galapagos National Park Directorate in 2012 has grown in number, and with it our knowledge about the biology of the fly and what techniques might be an option for its control. However, the research remained hampered by our inability to rear large numbers of the fly in the lab.

My challenge was to build on the work that I had started. I am working on solving the missing factors needed to successfully breed P. downsi in the lab. My first activity was to visit the facilities of the Screwworm Barrier Maintenance Program (COPEG), a highly successful program managed by the Panamian Government and USDA-APHIS. This plant produces millions of sterile flies weekly for the eradication of the screwworm fly. Absorbing all this knowledge, I returned to Galapagos to get to work.

Philornis flies

Philornis flies (© Julio Rodriguez)

We can now raise the fly in the laboratory with much more success than in the past, but this tricky fly is still giving us problems and keeping us on our toes. The diet for rearing larvae has been improved, but a key “something” to get flies to mate readily in captive conditions is still missing and we are trying all kinds of things to overcome this obstacle. We are a large group of researchers who are working together to figure this out and to find an effective control method for P. downsi. I have learned a lot about fly behavior and the English language no longer represents a difficulty in transmitting my opinions. My opportunities within the CDF have helped me fulfill my dreams. I look forward to continuing to help solve the puzzles of this fly and saving the landbird populations of Galapagos.

Paola Lahuatte

Paola Lahuatte is an Ecuadorian junior researcher and the coordinator of the Philornis lab at the Charles Darwin Research Station in Galapagos. 

Galapagos Conservancy has been supporting the Charles Darwin Foundation’s Landbird-Philornis project since 2013.

Read more about the conservation of landbirds in Galapagos. 



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