Scientists study the avian vampire fly (Philornis downsi) that lives in the Galapagos Islands

April 25, 2021
Isabel Alarcon

A group of researchers has managed to maintain and monitor the larvae of the invasive fly Philornis downsi in a laboratory. Photo: Courtesy Charles Darwin Foundation

Philornis downsi is now known as the avian vampire fly . This insect locates the nests of the birds and places its larvae, which then feed on the blood of the chicks and finally cause their death. With this method, the invasive fly has become one of the greatest threats to the conservation of 22 species on the Galapagos Islands.

With the aim that people become familiar with the danger that its presence in the archipelago represents, a group of national and international researchers decided to give it a common name. In three words, it sums up the behavior of the insect, which is believed to have been accidentally introduced to the Galapagos Islands less than six decades ago.

During this short time, the parasitic fly has caused the reduction of the populations of 20 endemic bird species, one native and one introduced. Of these, the smallest birds have been the most affected.

The mangrove finch, for example, numbers around 100 individuals in a small mangrove patch in western Isabela. This bird was previously threatened by rats and cats. The arrival of the Philornis worsened their situation on the islands.

Charlotte Causton, a senior scientist at the Charles Darwin Foundation and coordinator of the Philornis project, explains that research is currently focusing on the biology and ecology of this fly. More than 22 institutions from 10 countries have formed a team to evaluate various aspects.

Causton note that, after analyzing the images obtained with cameras, it can be observed that the vampire flies wait near the nest until the adult birds come out. At that moment, Philornis enters to lay her eggs. “It’s impressive,” says the researcher about the method.

To locate nests, the fly also uses its smell. With the help of researchers from the State University of New York, tests have been carried out showing that the insect reacts to the smell of birds

Once it finds the nests, the avian vampire flies lay their eggs. The larvae then settle in the chicks’ noses, where they make holes that affect the birds. When they are larger, they fall to the bottom of the nest and come out at night to suck the blood of the chicks.

This gradually deteriorates the animals’ populations. The chick develops anemia, becomes weak and asks for less and less food from its parents until it finally dies. Causton says the impact on bird populations is very serious, as all the chicks in the nest can die. During the nesting season of birds, it is estimated that the fly has up to four or five generations of insects.

Ways to control the vampire fly population are currently being sought. Photo: Courtesy Charles Darwin Foundation

To find ways to control their populations, the team of researchers is conducting laboratory tests. Under the direction of Paola Lahuatte, in charge of the Philornis downsi laboratory at the Charles Darwin Research Station, a method has been developed to breed fly larvae without the presence of a host bird.

So far nothing like this had developed in the world, says the researcher. The next step is to get the avian vampire fly to reproduce in the laboratory. For now, the adult flies are taken from nature in order to obtain their eggs. One of the most recent findings is that the moment the sun begins to go down motivates the flies to start copulating .

Causton explains that they may need chemical lures. Researchers at the State University of New York discovered that males produce pheromones to call females. That is also part of the conditions for the reproductive process.

These investigations, led by the CDF and the Galapagos National Park, will help establish better methods for population control of flies in the archipelago.

One of the ideas for this task is to apply an insecticide that inhibits the growth of insects, but which does not affect birds. The first results show that it can be injected at the base of the nest where the larvae are.

Together with researchers from the University of Minnesota, a study is being conducted to evaluate the possibilities of introducing a species of wasp that attacks only the vampire bird fly.

Read the original content from El Comercio at

Informing and sharing news on marine life, flora, fauna and conservation in the Galápagos Islands since 2017
© SOS Galápagos, 2021

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