May 18, 2018

In Southeast Asia, a newly identified ant species has a unique defense mechanism: it explodes! When threatened, or when in the grips of an enemy insect, the new tree-dwelling ant species Colobopsis explodens bursts toxic yellow goo from its abdomen, killing or chasing off its attacker. The ant dies in the effort, but it is an effective way of defending the colony.

A worker Colobopsis explodens ant strikes a formidable defensive pose. Credit: © Alexey Kopchinskiy, Pensoft Publishers

The self-sacrifice of the Colobopsis explodens ant may sound drastic, but it is not uncommon in the insect world. Many bees die after stinging an attacker, and certain aphids, termites, and other ants also practice autothysis—the act of self-sacrifice through explosion.

Ant colonies differ enormously in size. A colony may have a dozen, hundreds, thousands, or in rare cases, even millions of members. A colony usually has one or more queens. Ant queens are females whose chief job is to lay eggs. An ant colony also includes the ant young or larvae. Male ants, who have wings, live in the colony only at certain times of the year. Their only job is to mate with young queens, who also have wings. The rest of the colony consists mostly of workers. These wingless female ants do not lay fertile eggs but instead build the nest, search for food, care for the queen and the young, and protect the colony. Unlike queens, workers commonly leave the nest and can often be seen walking about on the ground or in trees.

The small, reddish-brown Colobopsis explodens workers are the ones who give themselves up for the good of the colony. During combat, the worker ant bites down on the enemy, lifts its lower body, and contracts its muscles so hard that its skin splits open, releasing sticky, toxic fluid from its abdomen. The explosion kills the ant, but the curry-smelling goo either kills or repels the enemy. If invading insects make it past the exploding ants’ front line, the colony has a unique second line of defense—worker ants with enlarged, plug-shaped heads. These ants gather together to barricade the nest’s entrance, keeping enemies out.

Exploding ants have been known for quite some time, but Colobopsis explodens is the first new species to be discovered since the 1930’s. Scientists do not know much about exploding ants, but this new species provides the opportunity to learn more.

August 29, 2016

A stream might seem like a great place to get away from biting and stinging bugs in tropical climates. In parts of Southeast Asia, however, it might not be a good idea after all. In June, scientists there announced they had discovered a new species of giant centipede. Unlike other centipedes, however, this species lurks in dark waters and is a powerful swimmer. The scientists published their description in the scientific journal ZooKeys.

Swimming centipede (Scolopendra cataracta)
Credit: Warut Siriwut, Gregory D. Edgecombe, Chirasak Sutcharit, Piyoros Tongkerd, Somsak Panha (licensed under CC BY 3.0)

Centipedes are a group of animals with long bodies and many pairs of legs. Although they vaguely resemble six-legged insects, they are not closely related to them. The narrow bodies of centipedes are divided into many segments (sections) that lie behind each other. Each section has two legs. Some centipedes have only 15 pairs of legs, while others have more than 180 pairs. A centipede’s head includes two antennae (jointed feelers) and a pair of jaws. The first pair of legs behind the head are modified into fangs. Centipedes use these fangs for defense or capturing prey, but not for walking. The fangs are called poison claws because a gland in the head fills them with poison.

The new species of swimming centipede is named Scolopendra cataracta. It is nocturnal (active at night). When it enters the water, it swims with powerful undulations (wriggles) of its body, similar to the way an eel swims. It is found in rivers in the Southeast Asian countries of Thailand and Laos and grows up to 8 inches (20 centimeters) long. Poison from the swimming centipede and its relatives is not fatal to humans, but stings can cause terrible pain in the affected limb for days. The poison is more than adequate to subdue small aquatic invertebrates, which the scientists assume are the swimming centipede’s usual prey. More research must be done, however, to study this animal and learn about its ecology.

The scientists who discovered the swimming centipede think that the nighttime waters of of tropical rivers and lakes hold many more surprises. Such habitats have long been observed during daylight hours, and many of the species that are active during the day have been catalogued. Finding creepy-crawly critters at night, however, can be a bit trickier. Who knows what other new species scientists may find while peering into moonlit waters?