Invertebrates have been less well studied than vertebrates in Armenia, as in most countries. Around 17,000 species of invertebrates have been recorded in the country, of which 90% are insects (key groups are shown in Table 2.10). Studies have been conducted on around 30% of invertebrates, and although the beetles (Coleoptera) are well studied, other groups such as Ephemeroptera (mayflies) and Neuroptera (lace wings) are not well known. A number of invertebrates are considered to be threatened including 7 molluscs, 15 grasshoppers, 1 homopteran bug, 10 hymeropterns (bees, wasps and ants), 40 butterflies and moths, 20 beetles and 4 flies.

A range of planktonic invertebrates are found in Armenia's water systems (totaling 124 species), including 46 species of rotifers (Rotatoria) and 78 crustaceans (Crustacea).

· Different rotifer species are associated with different water bodies. The most common include Brachionus rubens, Ketatella quadrata, Filinia longiseta, Pedalia fennica, and Conochilus hippocrepis. The greatest diversity of rotifers was previously found in the lakes Sevan, Arpi and Gilly (although the latter has since been drained).

· Among the crustaceans, both planktonic and pelagic forms are found. Common species include Chirocephalus skorikowi (in the vicinity of Lake Sevan, among other sites), and Lepthesteria dahalensis (Lori and Sevan regions). A total of 16 species of Phyllopoda are recorded from Armenia. Copepods include Diaptomus (7 spp.) and Cyclops (16 spp.).

In addition, a wide range of benthic species are found in Armenian water bodies (316 spp; Annex 2).

· A range of benthic species have been studied relatively well. These include: oligochaete worms, leeches, gastropods, bivalve molluscs, amphipods, dragonflies, mayflies, stoneflies, caddis flies, hemipteran bugs, flies, and beetles.
· A range of species are also found within the mud at the bottom of lakes and rivers. These include sponges (such as Ephidatia fluviatilis in Lake Sevan), flatworms, nematode worms, and copepods.
· Amphipods are found in a range of sites, among them are Unionidaes spp. (Ararat valley and warm reservoirs in the north), and Potamion potaimon (widespread in fast-flowing watercourses). In addition, and introduced species, Pontastacus leptodactylus, is proliferating in reservoirs and watercourses.

Table 2.10 Numbers of species of specific invertebrate taxa studied in Armenia