Pheidole - WikiHQ

thumb|An individual of species Pheidole megacephala.

Pheidole () is a genus of ants that belongs to the ant subfamily Myrmicinae. The genus is widespread and ecologically dominant. Many species in the genus first evolved in the Americas, while some, such as Pheidole indica and Pheidole megacephala, originated from East Asia and Africa, respectively. These species eventually began spreading across the globe. Pheidole megacephala is considered a particularly problematic invasive species. This caste is also notable due to the presence of wings, found in the queen ants as well as in the males.

A colony may contain one or several queens, and also in larger colonies of Pheidole morrisi, alates - virgin winged females and males - were found. Queens appear to allocate reproductive resources between queens and worker ants, and tend to favour one or the other in terms of allocation.

Pheidole_xerophila-major_minors.jpg|major and minor workers of P. xerophila

</gallery>

Morphology

Pheidole are ants which belong to the order Hymenoptera that includes organisms such as wasps, bees, ants and sawflies. Their body is divided into four main sections which include the head, mesosoma, waist and gaster that help differentiate them from other organisms in the order. Furthermore, the head allows us to tell apart the two physical worker castes. It contains muscle tissue, nervous system, the esophagus-pharynx, the propharyngeal glands, the postpharyngeal glands and the mandibular glands. This process is similarly followed during cultivation of food. Environmental cues also determines the role physical castes play in the colony.

Major workers

The distinctive major workers have earned the genus Pheidole the nickname of "big-headed ants". The major workers of a Pheidole colony, while they may look fierce, are often quite shy and are often the first to flee on any hint of danger. Many Pheidole species are the prey of parasitoid phorid flies that lay their eggs on the major workers; the fly larvae grow mainly in the head capsules of the victims, eventually decapitating them, and probably would starve in the bodies of minor workers.

In most cases, the major workers are employed within the nest to break up large food items, or outside to carry large items, such as seeds; many Pheidole species are ecologically important seed consumers ("harvesters").

pheidole purpurea face.jpg|alt=The head view of a "minor" worker of P. purpurea, with a scale to distinguish size|Minor worker

pheidole purporea minor body.jpg|alt=The top view of a "minor" worker of P. purpurea, with a scale to distinguish size|Minor worker, top

pheidole purpurea major face.jpg|alt=The head view of a "major" worker of P. purpurea, with a scale to distinguish size|Major worker

pheidole purpurea major body.jpg|alt=The top view of a "major" worker of P. purpurea, with a scale to distinguish size|Major worker, top

</gallery>

Minor workers

Minor workers typically get bigger over time, despite initially starting out as small "nanitic" individuals when the colony is first created.

Economic impacts and relationships with humans

Members of Pheidole hold an important role in the tropical agroecosystems that they are abundant in. Due to many Pheidole species being strong predators with aggressive tendencies, their nests are associated with a high presence of arthropod carcasses from their hunts. As a result, the soils that surround their nests show strongly improved nutrient density that improves their ecosystems.

Although the aggressive predation from Pheidole may benefit the ecosystems they originate from, many members of this genus are considered highly invasive species with Pheidole megacephala named as one of the 100 worst invasive species in the world. The invasive capabilities of Pheidole megacephala are tied to the aggressiveness of genus Pheidole, as within their native environments, they reside in an extremely diverse ecosystem with many other species compete against, many of which are also very aggressive. Finding themselves in environments with less diversity and decreased aggression from other species, lead to successful raids of local ant colonies.

Species list

The genus contains over 1,000 species.