A field guide for fruit flies

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Werner’s daughter assisted him in fieldwork collecting fruit flies. Image: Thomas Werner

By Carin Tunney

A common ancestor of fruit flies and humans emerged about 600 million years ago, long before the formation of the earth’s continents as we know them today.

Scientists discovered the link in the early 1900s, opening the floodgates to genetic research.

Fruit flies, or Drosophila melanogaster, are cheap, grow rapidly and are easy to mutate. Their genetic likeness to humans allows researchers to study diseases like cancer, diabetes and immune resistance.

That makes them a model species for genetic research, said Thomas Werner, a professor of genetics and developmental biology at Michigan Technological University in Houghton, Michigan.

Werner recently co-authored a book “Drosophilids of the Midwest and Northeast,” which gives fruit flies overdue accolades.

The book is the first to feature flies found primarily in the Midwest. It is also the most comprehensive guide to fruit flies of the Northeast and adjoining Ontario region, as it updates invasive types that arrived over the past 100 years.

The 250-page book contains hundreds of high-resolution images of fruit flies that simplify identification. Image: Thomas Werner

The book is a like a “Birds of North America” guide book for the tiny, winged bugs. It features 55 types of fruit flies with high-resolution images that capture the insects’ large, protruding eyes, intricate patterns on their thorax and the tiny hairs near the wings – details that could never be seen without a microscope. Since males and females aren’t identical, the book includes photographs of each.

Werner photographed each insect from at least 50 angles. Images of live flies are better than pinned images, he said. Many photos were taken while the insects were anesthetized with carbon dioxide. They were cleaned with tiny forceps and fixed to white paper with double-sided tape to make them easier to photograph.

Unfortunately for the insects, some photos also required dissection.

Photographing and editing images took an average of two hours per bug, which often meant working long into the night, Werner said. It took nearly five years to collect all of the images.

The book highlights 20 species that Werner caught in his backyard in Houghton using rotten tomatoes and bananas. His co-author John Jaenike sent him more from New York by FedEx within boxes to keep them alive.

Jaenike, a professor of biology at the University of Rochester, has been researching fruit flies for 40 years. His contributions include advice on trapping and fruit fly research.

The book is like having an expert in the field and can assist and inspire teachers and students to do their own research to identify various species, Werner said. It’s a launching point for fruit fly research.

Although the book is limited to the Northeast and Midwest, there are more than 4,000 types of fruit flies worldwide, according to the book.

But it’s not like simply strapping on binoculars and hitting the trail to ogle birds. Every species of fruit fly doesn’t buzz around a fruit bowl. The book includes techniques for trapping the insects with fruit and beer. It provides advice such as going into the woods after a rainfall to catch a species that is attracted to wild mushrooms that are toxic to humans.

Werner’s idea for the book came after a visit by Jaenike that included a walk into the woods to retrieve fruit flies from traps.

“Suddenly (Jaenike) looks into the net and he said, ‘This is the species you have from my talk …’  and the feeling was like what the heck is he doing? He doesn’t need a microscope to look at these fruit fly species,” Werner said.

“It was like an adrenaline rush in me. I felt envious in this moment. Envious with a triple espresso.”

Jaenike also contributed “interesting little factoids” about the 50-plus species within the book. The most interesting is his recent discovery of a non-native fruit fly in Rochester, New York.

Researchers discovered the invasive Phortica variegata fruit fly about two years ago in New York. The fly is known to carry dangerous parasites that can cause blindness in its native China. Image: Thomas Werner

The Phortica variegata is native to China and is known to transmit eyeworms that can cause conjunctivitis and blindness in humans and other species, Jaenike said. No flies carrying the parasite have been found in North America, but presence of the invasive species is concerning.

“This is going to catch people by surprise when people find out that this thing has shown up in the United States,” Jaenike said.

The authors hope the book may inspire people to collect fruit flies as a hobby.

“It’s a very approachable book and an approachable hobby that people can have. It is very, very easy. They can just do it outside your door and catch lots of fruit flies,” Werner said.

Werner’s 5-year-old daughter is already an enthusiastic collector.

“My collaborator (Jaenike) asked me to provide a picture of me with the fruit flies, and I told him, ‘John, I am sorry but I cannot find a single picture of me without my daughter in it because she has been sticking to my leg.’ So she is definitely hooked,” he said.

Werner’s daughter contributed hand-drawn images for the book. Werner said the idea was to keep it light and fun.

The book is free online, with a bound version in progress. The authors are adding additional species in upcoming versions. The book encourages readers to submit samples of missing species for inclusion.

Editor’s note: Capitalization of scientific names and a reference to when continents formed were corrected May 18, 2017.

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