Dinoponera cf. quadriceps - Tocandira / Giant Amazon Ant (Kempf, 1971)
Hymenoptera: Apocrita: Vespoidea: Formicidae: Ponerinae: Ponerini
Date: 22nd of July, 2018 at 09:12:53am
Location: Brazil, Ceará, Caucaia (Lat: -3.71, Long: -38.64)
Measuring with my finger (different specimen than the one in this post but with the same parameters and probably in the same species):
Dinoponera is a genus of ants in which is included the largest ant in the world. It's a genus strictly restricted to South America belonging to the order Hymenoptera, suborder Apocrita, superfamily Vespoidea, family Formicidae, subfamily Ponerinae and tribe Ponerini.
The subject portrayed measured somewhere around 3cm in length or more. All Dinoponera I met were never aggressive and accidents seem to happen with people who step on them leaving them choiceless. I tried to make her sting me but she just tried to flee. A field guide held one in his hand and she just tried to escape, never stung him. Under my experience, they were never aggressive towards very large bioforms.
My main doubt about this identification is differentiating Dinoponera quadriceps from Dinoponera gigantea. Both are found in Brazil; Dinoponera gigantea seems to have a confusing distribution status, while Dinoponera quadriceps are found in the same location I found this specimen. A person in a group told me she personally collected Dinoponera quadriceps in the exact location I found this specimen, which inclines the identification towards D. quadriceps instead of D. gigantea, even though both are probably possible. Their main distinguishing trait from Paraponera and Pachycondyla (considered a sister taxa to Dinoponera) is the size. Dinoponera are also distinguishable from Pachycondyla through the presence of two clypeal teeth on the laterals and rows of spines on the pygidium and hypopygidium. "Streblognathus bears some resemblance to Dinoponera, given its large size, subtriangular mandibles, clypeal teeth, and forward facing eyes, but Streblognathus has a novel fin-shaped petiole..." - anterior part of the abdomen that is elongated and straight and unites the rest of the abdomen, the gaster, with the thorax - "...and lacks the complex metapleural gland orifice, toothed tarsal claws, and hypopygial spines of Dinoponera, and is somewhat smaller.", as sourced further below.
There is no queen in the colony. They are replaced by a gamergate worker. Gamergates are viable reproductive worker ants that are able to reproduce with mature males in the absence of a queen. The alpha female is the highest-ranking member and reproduces with males from another nest at its entrance during the night. The male attaches the gaster (in ants, enlarged portion of the abdomen posterior to the petiole) inside the female's reproductive organ. Once copulation ends, the female will cut off the male's gaster which can't detach by itself. She pulls out a genital capsule that acts as a blockage to sperm and turns her unreceptive to other males, remaining monandrous. Mating is suicidal for the male.
Dinoponera can bite and sting. On the terminal end of the abdomen there is a sting that contains toxins. These are usually used by the alpha females on competing females and act as a trigger to the lower-ranked workers; these will try to immobilize the alpha's rival, but can fail. Dominated Dinoponera quadriceps will often retract their antennae. Dominance is also done through biting, blocking, gaster-rubbing, curling, and rubbing the antennae.
Low-ranking workers forage individually on littery soil but divide tasks within the nest. Lower-ranking workers process protein resources while higher-ranked females distribute food to the larvae. They feed on dead and live invertebrates, seeds and fruits. The entomopathogenic Cordyceps sp. fungus can parasitize Diponera.
They possess a strong venom that is expelled through the rear sting and is used to dominate large prey. The stinging is incredibly painful and the pain can last up to 48 hours. D. quadriceps' venom has antinociceptive, antimicrobial and neuroprotective properties, and is used to treat health problems such as back pain, asthma rheumatism and earaches. Anticoagulant activity seems to be present.
D. quadriceps' colonies are the largests in the genus, averaging at 80 workers. The nests are made of deep large chambers, possibly an adaptation to aridity. Their colonies in the Caatinga and Cerrado are mainly made under trees, probably an adaptation against aridity as well.
New colonies are formed through fissions, processes in which a group of workers leave the nest with their brood. This allows for a new high-ranking worker to become a gamergate. A high-ranking worker can also become a new gamergate when the current one dies or becomes unproductive.
Wheeler and Wheeler (1985) describes the larvae as: "Profile pogonomyrmecoid (i.e., diameter greatest near the middle of abdomen, decreasing gradually toward anterior end and more rapidly toward posterior end, which is rounded; thorax more slender than abdomen and forming a neck, which is curved ventrally). Body with numerous (114–160) mammiform tubercles, each with 2–25 short simple hairs; body hairs lacking elsewhere. Cranial hairs lacking. Mandible dinoponeroid (i.e. narrowly subtriangular in anterior view; anterior portion curved posteriorly; with or without medial teeth.)”
The male has a total length of ~21 - 22mm.
As for how to distinguish them from other species, check the source provided below.
Key to Diponera males: http://www.antwiki.org/wiki/Key_to_Dinoponera_workers (further reinforcing that this specimen is a D. quadriceps)
''Dinoponera quadriceps'' is a queenless species of ants in the subfamily Ponerinae. The species, known from Brazil, is similar to ''Dinoponera mutica'' and uses venom for subduing large live prey and defense. Its venom could be of use to the pharmaceutical industry.