The Dracula Ants

Our world holds tens of thousands of species of ants, and more are described every week. Most of these varieties provoke little excitement, but scientists working in Madagascar have found a new species of ant which is radically different from anything known before. The scientific name of these ants is Adetomyrma, but researchers are calling them 'Dracula ants.'

To understand why these ants matter, we have to understand the family tree of ants. The remote ancestors of ants were flies. Flies are millions of years old, and they live everywhere; but they do not live in groups, and they do not take care of their young. Some of these flies evolved into wasps, and wasps do build communities and feed their larva. Nonetheless, most wasps have stingers, and all wasps fly.

Ants do not have stingers; instead, they kill their prey and fight their enemies with toxins in their jaws. Furthermore, all species of ants do have wings, but only some ants in the colony have wings, and then only for a brief time. When ants start a new colony they send out young ants with wings to mate. These ants fly in patterns to attract each other, and breed quickly. Then the male ants die, but the females lose their wings and dig holes underground, where they start new ant-hills. They feed their young just as wasps do, but then their young feed them.

Most ants cannot digest solid food. Ants scurry around all day looking for flower seeds and scraps, but they do not eat what they find. Instead, they give their solid food to their larva. The larva digest the food and regurgitate it as 'honeydew.' This liquid is what the adults eat.

How did this evolve? How did adults who chewed their own food give rise to adults who got it out of the belly of a baby? What were the intermediate steps?

The science of evolution is full of questions like these. For example, we know that all living things began in the sea, and some of their descendants moved to the land to live; but which animal was it, and when? We cannot go to the beach and watch fish walk onto the land, so there are no witnesses; but there are many animals left which show how things must have gone. If we want a fish with 'fins like legs', we have the coelacanth, a fish with big meaty fins; these 'lobe-fins' look almost look like feet that were never finished. If we want to find fish who can walk on land, just a little, we can look at the famous 'walking catfish' from Asia; this fish has spines on its fins which allow it to climb out of dry puddles and find a new supply of water. If we want to find fish who can breathe a little air, we can look at the carp, which can gulp air and force it back over its gills when the water is too muddy to breathe. Finally, if we want to see a fish who can just plain breathe air like a land animal, we have the lungfish, a fish that can breathe water or air depending on the weather. Nobody will ever find 'the fish which got up and started walking on the land,' but if we look we can find most of the intermediate stages out there.

Often, these intermediate stages do not live on big continents or other places that get a lot of competition. Instead, they are often found on islands which more modern animals have never reached. Thus, Australia has marsupials, mammals like the kangaroo which carry their young in pouches, and monotremes, mammals like the platypus which lay eggs. The island of Madagascar is a hundred miles of the coast of Africa, and it also has primitive animals, such as the lemurs, monkeys with small brains and long noses like raccoons. Furthermore, Madagascar has the 'Dracula ant.'

The Dracula ant represents an intermediate stage in the history of ants. First, the Dracula ant has a simple waist, with only one joint between the abdomen and the thorax, like a wasp. Ants have compound joints because this allows them to wiggle through the narrow tunnels in their nests, which is not such a problem for wasps.

Dracula ants
The queen is the long ant in the upper left. The small brown ants are workers, and the white ants are larva.

The second difference involves wings. In all species of ants breeding is done by a special class of ants, and these ants have wings until they mate, and then lose them. However, female Dracula ants do not appear to have wings, ever, and scientists have still not figured out how they reach the places where they will form their new nests. The males seem to be more lucky. Instead of losing their wings, the males keep them for all of their lives. The sexes are also colored different: the females are pale, and the males are dark. This suggests that the females spend all of their time underground, but the males spend a lot of time, literally, 'out in the sun,' where their dark skin can protect them from ultraviolet rays. Scientists suspect that the male and female Adetomyrma do not mate on the wing, as other ants do; instead, the male ants fly to other colonies to find their mates.

The final difference concerns food. The larva do not create honeydew for their relatives to eat; instead, the older ants bite their backsides and - literally - drink their blood. Other species of ants will eat their children when they are hungry enough, but this eating kills the larva, and no species of ant relies on cannibalism to survive. Among the Dracula ants, however, all of the adults take blood from the offspring, and all of the larva are scarred.