Dolichoderus thoracicus
[Cocoa Black Ant, Rambutan Ant]
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Classification: | Kingdom: Animalia | Phylum: Arthropoda | Class: Insecta | Order: Hymenoptera | Family: Formicidae | Genus: Pristomyrmex |

There are wide varieties of bugs, either their nymph or adult forms that will attract ants. The ants protect the bugs from their predators and in return, the bugs produce sugary excretion that benefit the ants.

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These ants were nursing scale insects found on the leaf of a Sea Apple tree (Syzygium grande).

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The scientific name Dolichoderus bituberculatus whic I used in the past is a synonym of Dolichoderus thoracicus according to the AntWeb. This ant has been used as biological control agent to drive away mirid bug (Family: Miridae) from cocao tree (Theobroma cacao). Hence, one of its common name is Cocoa Black Ant.

In Singapore, this ant is common in nature parks and usually appears in large contingent protecting certain bugs including their nymphs or in long marching column. When I started to pay more attention to ants in late 2012, this ant caught my immediate attention because of its abundance in a nearby park which had preserved some wild areas from an old rubber tree plantation. Over the years when I frequent this park, I observed that this ant had gradually taken over the territories previously occupied by the weaver ants and the yellow crazy ants. It had even landed in my potted plant area since June 2015 supported mainly by the scale insects on the Cow Pea plant (Macroptilium lathyroides). Around March 2016, for unknown reason, the ant simply disappeared without a trace from the park. About a year later in May 2017, they began to re-appear in the park in small numbers.

Though the ants appeared to be about the same size in most of the colonies seen, I did see larger ones occasionally.

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The ant constructs its nest above ground level, usually on plants. Judging from the different shapes of their nests observed so far, it is likely to be opportunistic occupation of shelters or nests build by other insects or by taking advantage of existing structures One of the nests shown below was wrapped in a leaf of a Portia Tree (Thespesia populnea), which I suspect may belong to the Weaver Ant (Oecophylla smaragdina) in the past. One was constructed between 2 leaves (Suregada multiflora) that were in close proximity. The last one was in a deformed leaf (Heritiera littoralis) likely caused by bug infection.

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