Abstract:
Aneuretus simoni is a critically endangered endemic ant species in Sri Lanka. Five
preliminary laboratory experiments were conducted in May 2010 at room temperature to
study several biological aspects of workers of this species that were collected from the
Kirikanda forest in the Kalutara district. Five major and minor workers of A. simoni were
introduced separately to the cavities which consisted of decaying plant material and small
dead insects collected from the same forest, and honey. After an hour, all ants observed on
each food source in each setup were recorded. Three trials were conducted for each food
source. Soil temperature tolerance range of A. simoni at 40 % of soil humidity and soil pH of
6 was investigated by exposing nine major and minor workers each to twelve temperatures,
ranging from 19 - 35 °C, for an hour. Each experimental setup consisted of three 50 ml
beakers containing 5 g of soil collected from the Kirikanda forest. Three A. simoni workers
were introduced to each 50 ml beaker. These beakers were placed in a water bath to
maintain the soil temperature. A control setup was also maintained at room temperature.
The soil temperature tolerance ranged from 23 – 32 °C while no mortality was recorded in
the control.
To study the behavioural interactions between A. simoni and two other ant species (Pheidole
sp. 10 in author’s collection and Odontomachus simillimus) and a termite species
(Nasutitermes ceylonicus), which were common in the Kirikanda forest, a piece of rigifoam
with two cavities of 7 cm diameter and a connecting middle canal, was used. Initially, the
canal was blocked and ten major and minor workers of A. simoni were placed in one cavity
and ten soldiers and workers of the other species were placed in the other cavity. After half
an hour, the piece of rigifoam which blocked the canal was removed. Observations from
three trials conducted with each species were recorded. Pheidole sp. 10 and N. ceylonicus
avoided A. simoni workers while O. simillimus killed three, three and two A. simoni workers
in the three trials, respectively. It can be concluded that A. simoni workers were omnivorous
similar to the field observations of other researchers. Workers of A. simoni were eurythermal
at 40% of soil humidity and soil pH of 6. Aneuretus simoni can mutually survive with
Pheidole sp. 10 and N. ceylonicus, but O. simillimus appeared to be a natural enemy of this
species.