"Clouds" of "winged ants" at the Book Fair

In the summer, high temperatures and humidity are the perfect combination of conditions to initiate the “nuptial flights” of these “winged ants”. But what insects are these? The most common ants, of the Lasius species, which appear mainly in gardens or hunting for food scraps, are the workers . They are non-reproductive females and are responsible for everything that is essential for the colony, such as searching for food and maintaining the anthill. Those that have been seen in “swarms” flying around Parque Eduardo VII in recent afternoons are the queens and the “virgin males” .

When “specific atmospheric conditions” are present, in this case heat and humidity , explains Roberto Keller, curator of the insect collection at the Natural History Museum, both queens and males leave the nest and begin to fly. Despite this, this is a species that does not like heat very much, which explains why they usually appear either in the morning or late afternoon, near shaded areas in green areas such as urban parks, gardens or backyards.

The “winged ants” set out to reproduce with insects from different nests. In this case, the males and queens from the various colonies spread throughout the center of Lisbon fly in a “synchronized” manner in search of partners to form new anthills.

“ The ants themselves do absolutely nothing ,” continues expert Roberto Keller: “Males do not have a stinger in any species of ant — they never sting — and neither do queens, in this case.” At this stage of the life cycle of these insects, the concern is “finding each other and reproducing,” so the “only role” of males in the colony is reproduction; adults die a few hours after reproducing . After flying and mating, the queens “break” their wings and dig into the ground, where they build a chamber (anthill) to lay eggs and start a new colony. “This is the reproductive phase of the colony and, as they all emerge in synchrony from the different anthills, which are usually under the sidewalk, in gardens and parks, we don’t really see them. It’s only when they fly out that we realize we’re surrounded by ants,” he explains.

Concentrations of “winged ants” do not normally “occur in places where there are thousands of people” , and they tend to “find a place where they will not be disturbed”. Food is certainly another factor that contributes to the choice of meeting point. In the specific case of the Book Fair, ants “eat everything” , and can gather in rubbish bins or where there are food scraps scattered on the ground, as well as in the green space between the endless rows of book stalls.

There is no concrete explanation for why ants concentrate on food trucks that produce a specific type of food — that is, they no longer like fish or meat. Even so, Roberto Keller believes that these insects tend to concentrate in places where there are fewer people at a given time — which is what happened with the food truck that was forced to close on Monday. One thing is certain: the process “is not a phenomenon that lasts a month,” adds entomologist Carla Sousa, from the Institute of Hygiene and Tropical Medicine. The swarms are “very ephemeral and localized,” “they appear and disappear.” The wave of “nuptial flights” can last from hours to “several days”: but they rarely last more than a week.