How we started working on “rare” bee-killing flies

The most beautiful phorid flies are in the genus Melaloncha, also known as bee killing flies. I have no small bias in this statement, however, since I worked on them for several years and grew to be very fond of them.

Melaloncha punctifrons, female

One of the allures of these flies was their rarity when I first started. In all of the collections I surveyed, I could find only a few specimens, about 100 in total. There were many new species among these specimens, however, so I knew that the 32 described species was only the tip of the iceberg. But how was I to uncover the rest of that iceberg?

Many parasitic phorid flies seem to be attracted to masses of their hosts. Logically, aggregations of hosts should create aggregations of parasitoids, so Giar-Ann Kung and I decided to try to make aggregations of stingless bees, the known hosts of these flies. Monty Wood, a fellow dipterist who works on tachinid flies, told me that when he sprayed a mixture of honey, Coca-Cola, and water onto undergrowth vegetation in an attempt to attract his flies often attracted huge aggregations of stingless bees instead. Therefore we tried spraying honey and water, and were almost immediately successful in attracting bees, and eventually flies. There was one other required condition, however: it had to be in the sunlight, or the flies would not be attracted. This is contrary to most phorids, which tend to be more active in shade.

Melaloncha acoma attacking stingless bee

Once we adopted the honey spray and sunlight combination, we started collecting large numbers of these flies, eventually collecting thousands of them. Sometimes, we were almost too successful in attracting the bees, producing gigantic aggregations that made it impossible to breathe or see anything, necessitating the use of jury rigged bee veils. These consisted of an insect net placed over the head and sealed around the neck with rubber bands. Eventually, though, the tiny stingless bees would get in, and we’d have to beat a retreat to get the annoying things out of our eyes, ears, and noses.

Me wearing a jury-rigged "bee veil" in Argentina, 2003

It was all worth it though, as we ended up catching 50-100 Melalonchaper day at good sites, and found almost 150 new species. I think there are still many more out there to find, so we keep spraying honey wherever we go in the tropics, and keep finding the beautiful, but deadly (to bees) bee-killing flies.

Melaloncha xanthocauda, femal

Melaloncha berezovskiyi, female

Melaloncha acoma, female

Take your watch to the field

I am sure it makes perfect sense to bring your watch into the field to keep track of the time. That is not why I am advocating this practice, however. A watch once helped us make an important new observation on bee parasitizing flies in the tropics.

One unavoidable fact of tropical fieldwork is that you will stink. You sweat your clothes out within the first 10 minutes after breakfast, and remain damp and moldy all day until you hit the showers. It is impossible to wear clothes for more than one day without them getting rank and disgusting. You can either bring enough clothes to change all of them every day, do lots of laundry during the trip, or resign yourself to having some of your clothes remain not suitable for indoors and fine dining.

Things that you wear or sweat on day after day buildup in particular fragrance. For instance, my collecting bag is always covered with butterflies in the field, probably because they mistake it for a piece of carrion. Other items can be the same way.

My collecting bag swarming with bees, flies, and butterflies. It stank.

In 2001, Giar-Ann Kung and I were in Colombia with some colleagues, and it was incredibly hot and humid. We were after bee killing flies of the genus Melaloncha, which we were trying to attract with honey. Placing honey on the undergrowth attracts large numbers of bees, and once we had large numbers of bees, we hoped that the parasites would arrive as well. Problem was, it wasn’t working. The bees were much more attracted to Giar-Ann’s watch, which really stank. She took it off and put it on sheet that we had placed in the field and the bees visited it avidly. Suddenly, against the black background of the watch, Giar-Ann noticed a tiny yellow shape curling its abdomen and running towards tiny bees. She collected the fly and showed it to me – it was a female Styletta crocea, a rarely collected species whose lifestyle was completely unknown. I doubt if we would ever have seen the fly without the black watch in the background. Later, we collected Melaloncha specimens, but that Styletta was our first big break of the bee parasite project.

female Styletta crocea

It never ceases to amaze me how events unfold during a research program or field trip. No matter how much you prepare, invariably which you thought would work doesn’t, but something completely different appears or is found. It’s part of the reason why fieldwork and research remain compelling and exciting for those of us who aspire to make new discoveries.