Trechisibus antarcticus is a flightless ground beetle up to 0.5 cm long and 10 mg live weight (Todd 1997).

The introductions of predatory carabid beetles such as Trechisibus antarcticus to South Georgia may provide an illustration of the potentially rapid ecosystem changes caused by the introduction of foreign species. They also provide a form of natural experiment testing ecological theories about the consequences of introducing new trophic levels into natural ecosystems which would otherwise be impossible (Convey et al. 2006a).

In South Georgia, sub-Antarctica, Trechisibus antarcticus is invading the coastal lowland areas and building up local high densities in the dominant tussock-forming grass Parodiochloa flabellata (Ernsting et al. 1999). Together with an ample food supply in the form of small arthropods and beetle larvae and a vacant niche for arthropod predators, the benign microclimate of the tussock vegetation may explain the success of this and similar predator beetle introductions in South Georgia (Brandjes Block & Ernsting 1999). Compared with other habitats, tussock provides a buffered and stable thermal regime that will facilitate the spread of T. antarcticus throughout the lowland areas (Brandjes Block & Ernsting 1999).

Laboratory experiments have shown that the carnivorous Trechisibus antarcticus is a voracious predator, feeding on beetle larvae and other soil arthropods (Ernsting et al. 1999). T. antarcticus feeds on various mites and springtails the larvae of the herbivorous beetle Hydromedion sparsutum on South Georgia (Todd 1997).

In the same coastal areas in South Georgia where Trechisibus antarcticus has colonised, lives an endemic detritivorous beetle known as Hydromedion sparsutum (Perimylopidae). It is common especially in and beneath the tussock grass. The first three larval instars (stages) of H. sparsutum are easily taken prey by the carabid T. antarcticus. On sites colonised by the carabid, total abundances of larval and adult H. sparsutum are far lower (Ernsting et al. 1999).