Not Quite an Insect

Campodea spp.

Even though there are only four species present in Ireland (all from the genus Campodea (1)), diplurans are often observed in soils, where they are perfectly adapted to life there feeding on live prey and decaying organic matter amongst the leaf litter. With their lack of eyes, lack of pigment, long tapered bodies and long antennae they resemble miniature centipedes, but their six legs on their three segmented thorax tell another story. Diplurans are hexapods, and while often placed in the class Insecta, they should really be seen as insects' closests relative (2). While sharing many features with insects (body divided into head, thorax and abdomen, three pairs of walking legs, and a segmented abdomen devoid of legs), they are distinguished from insects by having antennae devoid of a chordotonal sensory organ in the pedicel and by the lack of an appendicular ovipositor and of a median unpaired caudal filament (2). Often referred to as 'two pronged bristletails', this name is derived from presence of only one pair of caudal appendages, the cerci. There are about 1000 species of diplurans described present throughout the planet in all but the harshest areas (deserts, polar regions and areas above 3500 metres). Three major lineages exist: Campodeoidea, Projapygoidea, and Japygoidea (3).

References:

1. Ferriss et al., 2009. Irish Biodiversity: a taxonomic inventory of fauna
2. Kock, 2009. Encyclopedia of Insects (Second Edition) pp. 281-283
3. Luan et al., 2004. Pedobiologia 48 pp. 453-459