A fascinating recent publication deals with the potential of species delimitation in Lepidoptera via CO1. An international cooperation, with the participation of experts from the Tyrolean State Museums, could show that DNA barcoding is an efficient approach to determine the vast majority of European Lepidoptera.
Every determination is eased by reciprocal monophyly between species. In the absence of the latter experts are in demand to find possible explanations. The publication gives a nice overview on possible reasons for observed para- and polyphyly between species.
Mutanen, M. et al. (2016). Species-Level Para- and Polyphyly in DNA Barcode Gene Trees: Strong Operational Bias in European Lepidoptera. Systematic Biology, 65(6), 1024–1040.