Peatlands have their own, specific insect fauna. They are a habitat not only for ubiquistic but also stenotopic moths that feed on plants limited to wet, acid and oligotrophic habitats. In the past, raised bogs and fens were widely distributed in Europe. This has changed since 20th c. Due to irrigation, modern forestry and increasing human settlement, peatlands have become isolated islands in agricultural and urban landscape. Here we analyse the flora in a degraded bog situated in a large Lodz city agglomeration in Poland in relation to the diversity and composition of moth fauna. Over the last 40 years since the bog has been protected as a nature reserve, birch, willow and alder shrubs replaced the typical raised bog plant communities due to the decreased water level. The analysis of moth communities sampled in 2012 and 2013 indicates dominance of ubiquistic taxa associated with deciduous wetland forests and rushes. Tyrphobiotic and tyrphophile moth taxa were not recorded. We conclude that the absence of moths typical of bog habitats and the dominance of common, woodland species are associated with hydrological changes, the expansion of trees and brushes over typical bog plant communities and light pollution.

The material was collected from spring of 2011 to late autumn of 2012. At the Różana 30B street (51˚48'00"N; 19˚18'42") (R) site, a Robinson trap with mercury bulb was used, and sampling took place from spring 2011 to spring 2012. Catching was carried out regularly at two-week intervals from 9:00 pm to 3:00 am. The catch at Torfowa Street (T) (51˚48'08"N; 19˚17'38") took place by a standard light trap with mercury-incandescent bulb and white canvas from spring to autumn 2012 at two-week intervals. The light trap at Torfowa st. took place between 10.00 pm and 12.00 pm. The data matrix presenting a list of taxa collected at R and T sites is included in appendices Tab. S1 and Tab. S2. The Heterocera were poisoned with ethyl acetate and then frozen until preparation. The habitat and host plant preferences of collected moth species were obtained from literature data, especially those focused on central European fauna. 

To recognise an assemblage pattern in caterpillar host plants of the reported taxa, a series of analysis was used. 1) NMDS analysis based on Bray-Curtis formula was conducted on all collected moth species as “samples”, and for each species up to three main host plants as “variables”. As NMDS divided taxa into two main moth groups – A and B, and the out-group O, 2) one-way SIMPER analysis indicating main host plants for each of group was conducted using Bray-Curtis similarity index and 100% cut-off. 

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