Shaped like saucers, or concave shields, and covered with camouflaging layers of debris, the heads of two "door head" ant species are found to differentiate them as new taxa. They use their peculiar features to block the entrances of their nests against intruders like other predatory ants and invertebrates.
Being only the second case of such highly specialized morphologies discovered in Africa, the new representatives of the genus Carebara have been retrieved from sifted leaf-litter collected in rainforests in Western Kenya and the Ivory Coast.
Because of difficulties usually met while studying and identifying ants through dry specimens retrieved from standardised, passive collection methods, the two new species have so far been taxonomically misplaced. The new discovery was made by an international research team, led by Dr. Georg Fischer and Prof. Evan Economo, Okinawa Institute of Science and Technology Graduate University, Japan. The findings are available in the open access journal ZooKeys.
The "door head" ant individuals are a special worker subcaste that stands out among the other ant colony's workers, who are responsible for vital tasks such as foraging and brood care. Dr. Georg Fischer and his colleagues analysed the herein described species with next-generation DNA sequencing to show that all different subcastes belong to the same species, despite their highly differing morphologies.
To assure the safety of their nestmates, the queen and the larvae, the two new species have evolved the special worker subcaste with heads covered by a layer of debris such as soil or even organic material, so that they blend in with their surroundings. While the shape of their heads allows them to perfectly fit into the nest entrance, the special armor shields their vulnerable eyes, antennae and mouthparts, as well as highly reduces the chance of enemies intruding into the nest.
The new Carebara species have been given the names C. phragmotica and C. lilith. The former is derived from the term phragmosis, in relation to the special function of their head shape, while the latter comes from the name of a female demon in Jewish mythology.
Fischer G, Azorsa F, Hita Garcia F, Mikheyev AS, Economo EP (2015) Two new phragmotic ant species from Africa: morphology and next-generation sequencing solve a caste association problem in the genus Carebara Westwood. ZooKeys 525: 77-105. doi: 10.3897/zookeys.525.6057