L. dubia co-occurs with L. rubicunda but seems to be more abundent based on exuvia observations. Larvae overwinter 2-4 times.
L. dubia exuviae were common in lake Mustinlampi, where I found only a few exuvia of L. rubicunda.
Lake mustinlampi still has some very beautiful shores with floating peat vegetation, a habitat for L. dubia. In fact, in allmost all investigated lakes with peatbog vegetation L. dubia exuviae were found.
Both species are difficult to distinguish, but the hamulus of L dubia is more straigth compared to L. rubicunda.
Figure 1. Distribution map exuviae L. dubia.