Caddisflies (Trichoptera) are a globally diverse group, yet they remain understudied in many developing countries. The biodiversity of the freshwater ecosystems of Georgia is under-researched (NBSAP 2014; Japoshvili et al. 2016; Mumladze et al. 2020), with aquatic insects, including caddisflies, being no exception. This is reflected in over 100 caddisfly species having been added to the Georgian list in the 2020s alone, and it is believed that many more remain to be discovered (personal communication with János Oláh).

The history of research on Georgian and Caucasian caddisflies dates back to the 19th century with the work of Robert McLachlan (McLachlan 1869, 1876). However, the most substantial early contributions came from Martynov, who described a total of 35 new species and recorded 46 species for the first time in Georgia (Martynov 1913a, b, 1915, 1918, 1925, 1926, 1927, 1934). In the following decades, various local and foreign researchers contributed by describing 18 new species and recording several species for the first time in Georgia (Elanidze 1946; Murvanidze 1948; Lepneva 1956, 1958, 1961; Botosaneanu 1967; Zosidze 1973, 1999a, b, 2002; Malicky 1974; Malicky and Oláh 1979; Mey and Müller 1979; Mey and Joost 1982; Oláh 1985; Spuris 1988; Pankvelashvili et al. 2020).

A new era in the study of Georgian caddisflies began in 2019, driven by János Oláh’s exceptionally productive work describing over a hundred species (Oláh et al. 2019, 2020; Oláh and Vinçon 2024). Although clearly considerable progress has recently been made, there remains much to explore in the study of local caddisflies. Through our investigation of the caddisfly fauna of Georgia, we present two additional species: Calamoceras illiesi Malicky & Kumanski, 1974, and Mystacides azureus Linnaeus, 1761, both of which are recorded for the first time in Georgia (Fig. 6).

The larva of Calamoceras illiesi was collected using a hand net. The imago of C. illiesi and Mystacides azureus were caught using a butterfly net. All specimens were preserved in 95% ethanol and then stored in a freezer at -22 °C. If a detailed examination of adults was necessary, the abdomens were cleaned in a 10% KOH solution and transferred to glycerol for further preservation and storage. For identification of the larva and imago of C. illiesi, the descriptions by Sipahiler (2013) and Malicky (2004) were used, while for M. azureus, the description by Malicky (2004) was utilised. All examined material is kept in the collection of the Museum of the Institute of Zoology, Ilia State University, Tbilisi (hereafter IZISUT).

The map of sampling locations was made in the QGIS software (QGIS Development Team, 2024). Photos of the preserved specimens were taken using a Canon EOS 60D camera with a Canon EF-S 60mm f/2.8 Macro USM Lens. Digital images were prepared using Zerene Stacker image stacking software and Adobe Photoshop CS6.

With the two new species reported in this paper, the diversity of Georgian trichopteran fauna has increased to 250 species grouped into 55 genera and 19 families. Of these, 109 species (≈44%) are endemic to Georgia, while 141 species (≈56%) are endemic to the Caucasus. Among the species-rich families, Philopotamidae stands out with a particularly high level of local endemism, with 16 of 26 species (61.5%) found only in Georgia. An additional 37 Caucasian endemics remain unrecorded in Georgia, reinforcing the need for further research.

An unknown representative of the genus Calamoceras was recorded by Martynov (1913) in Akhali Atoni (western Georgia) (Fig. 6). We assume that this record probably belongs to C. illiesi, however, this assumption requires further confirmation, given the high diversity of trichopterans in the region.

In terms of its habitat, despite extensive and repeated sampling, C. illiesi larvae were only found in one stream, which fully matches the species’ known habitat preferences (Sipahiler 2013). The specimens were located at the edge of a small pond (1–2 m wide) formed by a mountain spring, where the slowed flow allows accumulation of woody debris and leaf litter (Fig. 5). Larvae were absent from nearby streams, suggesting a small, microhabitat-dependent population and highlighting its vulnerability. Consequently, protecting this known habitat is essential for the conservation of this rare species (Evtimova and Kenderov 2016).