Pheidologeton diversus (Ph. D) is a eusocial insect and individuals have continuous allometric variation in size and morphology to facilitate task allocation and partitioning of work. Minor workers are between 1.3 and 2.5 mm in length, but major workers are much larger. Between the smallest minor and largest major workers there are many intermediate forms. The largest workers can have heads approximately 10 times larger than that of their smallest counterparts. The dry weight of a large major worker can be approximately 500 times heavier that of their smallest counterparts. These size-related morphological differences correspond with their division of labor. For example, small, young, minor workers specialize in caring for the larvae but extend their activities as they grow older and increase in size.
Source: Wikipedia - http://upload.wikimedia.org/wikipedia/commons/c/cc/PheidologetonCastes.jpg
Source: Courtesey of Vincent of the Netherlands, aka "UneXisted"
Minor workers have yellowish brown to reddish brown bodies. Their mandibles each have five "teeth" and their antennal scapes are short and do not exceed the posterior margin of the head. Minor workers have rectangular heads with weakly convex posterior margins in full face view. Major workers have reddish brown to blackish brown bodies. Their heads are proportionately larger and almost square with convex posterior margin in frontal view. Mandibles of major workers are large and triangular, with an acute apical "tooth". Their masticatory margins lack distinct "teeth". Their eyes are relatively small and their antennal scapes are half as long as their heads.
A minor worker and a major worker.
There are also majors whose function is to protect the nest and foraging trails, to cut up insects and preys, and to act as food storage.
Some workers and a major soldier
A super major soldier
Nesting Behavior
Ph. D forms large colonies which are often found in soil, under rocks, beside large trees, walls, or building. Their nests are located in shady areas where humidity is higher, as workers die out quickly in dry conditions. In younger colonies, nests usually contain a single large chamber where brood and queen reside. Nest entrance is often directly above. In larger, or mature colonies, the nest spans across a very large area with a complex myramid of tunnels across the nest. There are multiple chambers, but queen(s) and brood will often reside in the largest and deepest chamber, which can be up to a meter below the ground.
A young nest, the queen is hidden out of the picture.
[picture of large nest outdoors – east coast]
[picture inside a nest – take one from my colony with brood, in soil]
This specie is both monogyn and polygyn, meaning that a single nest can contain one single queen, or more than one queens. In the wild however, at least in Singapore where I live, nests are founded by single queens. Additional queens are usually adopted only when the colony reaches maturity and a delate queen is subsequently “invited” to join the nest by the existing queen and her colony (for more info, see nuptials page).
In the wild, I have personally uncovered many young colonies to date under rocks, logs etc to date, and all of them contained single queens. However, under controlled conditions, when two newly mated delates were placed together in a small tank of soil, they decided to form a nest together. A recent experiment conduct by myself derived a record of 7 queens in a single founding nest (I had placed 19 newly mated delates in a glass tank full of soil, they were all from a single nuptial flight).
[picture of young colony – must find]
[picture of multiple queens – must find]
Foraging and Food (Source: Wikipedia, edited with own information)
This species preys on small animals such as insects and also collects nectivorous materials such as palm oil seeds, coconut and other (fresh or rotten) tropical fruits available in South East Asia. These ants regularly forms long columns for foraging and sometimes roof these trails with arcades constructed of soil particles. This is necessary as the workers die quickly in dry conditions and soil tunnels help maintain humidity. They use pheromone trails to maintain these lines and if these trails are obstructed it causes chaos and crowding. One study showed that 98% of individuals failed to cross an obstacle in the foraging path and that eventually the column creates a detour around such obstructions.
[picture of foraging trail – must take from telok blangah]
Source: Wikipedia
[picture of workers eating seeds/fruit – must take]
Geographical Range (Source: Wikipedia)
Ph. D is widely distributed from India through Southeast Asia to Taiwan and the Philippines. Field records of it occurring Japan are limited although it has been found on two very southern points: Okinawa Island and on Chicchi-jima Island. Specimens taken at the Camp Zama U.S. Air Force base in Kanagawa Prefecture are believed to have originated from commercial introduction from South East Asia.
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