Invertebrates in general and insects, in particular, are often used as bioindicators. They are most effective when highlighting subtle differences between habitats, not obvious when examining higher plants and vertebrates. They represent one of the most diverse elements of the ecosystem.
To assess the conservation importance of Barna Woods for invertebrate communities, the biodiversity study focused on flies (Diptera) and beetles (Coleoptera).
The vast majority of Diptera (flies) and Coleoptera (Beetles) familes collected during this survey are typical faunal components of woodland ecosystems and are likely to be present in most woodlands in Ireland.
Barna Woods provides a number of key resources for these various taxa to survive. These include dead wood, leaf litter, fungi, living plants, decomposing vegetation, pollen, carrion and other invertebrates. The presence of the Alder Woodland and the various streams also greatly increases the invertebrate richness as it provides a suitable habitat for a range of aquatic invertebrates to colonise the area. Without these aquatic systems in the woodland, these freshwater communities would obviously be absent.
This is only the third time that this snail-killing fly has been found in Ireland and is the first record for the species in Co. Galway. In the U.K. T. freyi is of notable conservation importance and is classified as a Red Data Book species (Ball and Mc Lean, 1986).
Family Periscelidae which is a relatively rare fly taxa was recorded at Barna Woods in the south wood.
This carabid (beetle) is most often recorded in Ireland on sandy soils close to the coast. It has also been collected in open woodlands, gardens and agricultural grasslands. It is widespread in the United Kingdom, but in Ireland it has a local distribution. In Barna woods this species was recorded in the beech dominated woodland north of the carpark and in the southern Wood. Records of the species over the past decade are uncommon.