This is a Hydropsyche species which we will never have identified. It is one of the five rare species in the Low Countries, for it prefers faster streaming waters. In the park nearby there is a small stream and probably it is the only place where a Hydropsyche like this could live. It has the typical features of its genus: it has long, ringed antennae, it is brown and there are numerous small yellow spots in the brown, much more and also smaller ones than in the previous species Hydropsyche angustipennis. So there is nothing more we can tell you about it, for we don't know the exact species.