Ábrahám Levente: Biomonitoring a Dráva folyó magyarországi szakasza mentén 2000-2004 - Natura Somogyiensis 7. (Kaposvár, 2005)

Uherkovich, Ákos - Nógrádi, Sára: Middle-term changes in caddisfly (Trichoptera) communities of the Hungarian part of Drava river during the years 1992–2004 - Tegzes együttesek középtávú változásai a Dráva magyarországi szakasza mentén, 1992-2004 folyamán

UHERKOVICH A. & NÓGRÁDI S.: CADDISFLIES (TRICHOPTERA) COMMUNITIES 59 There are a few species which became more frequent at Vízvár and along other sections of the river only in the last years. Both Adicella syriaca Ulmer (Fig. 14) and Silo piceus Brau. (Fig. 15) were unknown or very rare in the nineties. In 1999 they appeared and soon they became permanent and not rare members of community. Although the quantity of collected material was considerable during some years at Drávapalkonya and Vejti, the collecting period was too short there, therefore changes were not shown clearly. At Drávasztára we sampled through years, but the collections of some years were not satisfactory. During the first half of nineties the quantity of Oecetis notata Ramb. was outstanding, later it became less frequent. The other species discussed also in the previous sentences show similar run of activity, with few regularity. The most valuable species of the Dráva river is the strictly protected Platyphylax frauenfeldi Brau., which has a stable population between Szentborbás and Ortilos. Taking all data from this region into consideration we are presenting its activity, i.e. the graph of its all collected specimens. It seems that there were some outstanding years in the frequency: 1989 (when the light trap functioned at Szentborbás), 1992 and 1992 (light trap at Ortilos), 1996 (a very advantageous year for night collections) and 2000 (rather lucky meteorological situation in 30th and 31st October at Vízvár and Ortilos, when 46 specimens were collected on light). We also visited the sites in 1998 and in 1999, but no adults were caught, and the number of adults we only few in the years 20012004 (Fig. 16). This graph also shows that the circumstances influence the catch essentially. We also try to show the activity of two other characteristic species, on the basis of all data of Drava region, from the year 1982. Trichostegia minor Curt, is a characteristic species of the region. It lives in forest fens mostly, and it is on wing from May until September, interrupted by a short summer diapause. Although it is not a rarity, we cannot collect its adults every year. Limnephilus stigma Curt, has a similar ecological character, but it is a very rare species. The first Hungarian specimens were collected only in 1995 (Jósvafő), first specimens were taken in 1996 along Dráva region (NÓGRÁDI 1998). We visited its site (Gyékényes) several times during last years, but it was collected only in few cases, most specimens in 2004 (Fig. 17). Besides these four mentioned species we can sketch the graph of other species, as well. They do not show any regularity. We cannot settle whether either the unsatisfactory sampling or the changing circumstances cause the irregularity of graphs. Fig. 16. Activity of Platyphylax frauenfeldi Brau, in the Dráva region, 1989-2004. 16. ábra. A drávai tegzes (Platyphylax frauenfeldi Brau. ) aktivitása a Dráva mentén, 1989-2004.