Dear Vesela, thank you very much for your contributions.

Mrs. Evtimova is right, There is a good identification key of aquatic insect larvae by Rudolf Rozkošný published in 1980 in Prague in Academia.

Each species is an indicator, you have just to intertpret correctly the field data basing on knowledge of the secies auecology.

I agree with the above answers, in that a species has its own range of tolerance of environmental conditions in its home range; hence ideally calling for further surveys of aquatic invertebrates and water quality for a region of interest. Having said that, there are some general principles that make Trichoptera, Plecoptera (stoneflies) and Ephemeroptera (mayflies) indicators of good water quality and 'intact' forested watersheds - for instance, if there is a lot of soil erosion in the catchment (deforestation/agriculture/roads etc), that washes down into the stream and covers the stony bottom, these insect larvae would have no habitat left (the underside of streambed stones), and hence would disappear from the stream. hence the presence of caddisfly larvae indicate an absence of major soil erosion over the past year.

I think that they are Sericostomatidae, maybe Sericostoma, but you have to check the larvae with specific keys, e.g. in the book Invertébrés d'eau douce (Tachet, 2010). Some of them seem pupae case, look at the circular structure closing the case, typical of this family.

About the use of the invertebrates for checking the water quality, there are several indexes that use the presence of the families of macroinvertebrates found in samples (e.g. BMWP, in Armitage, P. D., Moss, F., Wright, J.F. & Furse, M.T. 1983. The performance of a new biological water quality score system based on macroinvertebrates over a wide range of unpolluted running-water sites. Water Research, 17: 333-347). For example, the value of this family  (Sericostomatidae) for calculating this index BMWP is 10, the maximum, but you have to add all the families of the sample (e.g. trichoptera, plecoptera, ephemeroptera, and the rest of groups). The presence/absence of the families is supposed to reflect the possible disturbance of the habitat for a period of time previous to the sample collection. More sensitive species could dissapear from samples if this disturbance is strong enough, so the value of index will decrease.

Best regards

Maria

As a general lotic trend, sand-cased caddisflies are considered to be highly intolerant of pollution and riparian impacts:

Vadas, R.L. Jr. 1997. Assemblage structure of riparian and drifting invertebrates along environmental gradients in two streams of southern British Columbia. DOE FRAP (Canada Department of the Environment, Fraser River Action Plan) 98(28): 62 pp. (http://research.rem.sfu.ca/frap/9828.pdf).

Vadas, R.L. Jr. 1998. Human impact on aquatic and riparian ecosystems in two streams of the Thompson River drainage, British Columbia. Pages 13-30 in M.K. Brewin and D.M.A. Monita (eds.). Forest-fish conference: land management practices

affecting aquatic ecosystems. Natural Resources Canada, Forest Service,

Northern Forestry Center Information Report NOR-X-356. Edmonton, AB (http://cfs.nrcan.gc.ca/pubwarehouse/pdfs/11639.pdf).

-Bob Vadas, Jr.

Trichoptera are considered to be sensitive to pollution however determining water quality using one /order/family/species alone is not a true indication. Even within the caddis taxa the signal/sensitivity grades vary.  In Australia we use the Signal 2 Scoring System for Macroinvertebrates, Author Bruce Chessman.  This index would be similar to others developed in North America and Europe.

Regards Karen

Karen O'Neil is correct that higher-order taxonomic classifications are less-sensitive indicators of human impacts, as my cited BC work showed. But it's somewhere to start, especially in lesser-studied countries like Turkey. Also note that lower-order taxonomic classifications for zoobenthos may also be more relevant to specific human impacts, rather than have general utility.

Caddis fly larval cases in an of themselves do not necessarily indicate high water quality.  Anecdotally, one of the more amazing things I've ever seen is a perfectly formed case of spherical beads.  I was sorting preserved samples that had been treated with rose Bengal so the matrix glowed bright hot pink with beautiful crystal spheres.  It turned out to be caddis-fly cases, down stream from tall (coal fired power and coke) plant stacks that were maintained and cleaned by injecting glass beads into the flue to clean the stacks.  As remarkable as they were, a faculty member at Wheeling Jesuit University, took that one step further by allowing caddis fly larvae in aquaria to have access to  semi-precious stones.  Of course the result of the larval work were beautiful jewelry.

I think it could be as indicator for clean water.

There are exceptions to every rule, which makes biology both interesting and challenging. I don't know if every sand-cased caddisfly species would benefit from industrial spherical beads, but one would presume that conditions aren't eutrophic or highly toxic downstream. Has Francis Reilly's observations been published?

Hello,

A few close-ups of the dorsal surface of the head and thorax, plus one of the legs (the third leg attached to the metathorax will do) should allow a determination at least as far as Family level, if not genus & species. My impression (from size and general shape, plus a largely darkly pigmented head) is that these are Sericostomatidae, or a sand-grain cased limnephilid such as Drusus sp., both of which are fairly sensitive to reducing water quality and fine-sediment load.

Trichopterans are generally indicators of good water quality hence they are used in the EPT (ephemeroptera, plectoptera, trichoptera) metric as one of several metrics that can be used for assessing biological water quality. It would be best to use a range of taxa with associated water quality and other environmental data to develop a set of simple correlates. 

yes Ttrichopteran are good indicators of  water quality and that why they are included in EPT for water quality assessment. There are  different species, some of them  case makers while others non case makers .The larval forms  could be identified based on the   presence of three  dorsal plates with out hump family-Hydropsychidae, with two dorsal plates with out any hump as in  family Brachycentridae,,with dorsal and lateral hump in family Odontoceridae.

The "soft" surface and sightly curved form are typical of the family Sericostomatidae. In the british BMWP index, this family is in the most sensitive group 9/9. In the French IBGN index, it is classified in group 6/9, that is, quite sensitive.

Thanks dear Marc

I agree with the comments in general.  One word of caution:  when you look at whole samples, if you see abundant hydropsychid caddisflies it can indicate particulate loading.

I worked and identified some of  them in Iran, Austria and UK and found that they are good index for clean water. Do not hesitate them as water quality index.