The genus Wesmaelius is divided into two subgenera Wesmaelius and Kimminsia. These subgenera can be differentiated by the number of branches of R and the general shape of the male and female genitalia (see image below). For Wesmaelius click here, for Kimminsia click here.
Wesmaelius (Wesmaelius)
There are two species in the subgenus Wesmaelius, Wesmaelius (Wesmaelius) concinnus and Wesmaelius (Wesmaelius) quadrifasciatus. These two species can be differentiated from one another by the presence or absence of a thoracic stripe, the patterns on the veins and the male and female genitalia (See below image).
Wesmaelius (Kimminsia)
There are six species in the subgenus Wesmaelius (Kimminsia). To start to divide these species you can see whether there is a pale stripe on the thorax (see below image). If there is no pale stripe (click here), if there is a pale stripe (click here).
If there is no pale stripe on the thorax, there are two choices of species Wesmaelius (Kimminsia) mortoni or W. (K.) balticus. These species are differentiated on features such as the presence or absence of spots on the veins, and the structure of the male and female genitalia (see image below). W. (K.) mortoni is potentially extinct in the British Isles, last recorded in 1898, therefore if you think you have this species please retain the specimen and contact the Recording Scheme for verification.
For the four species with a pale stripe, Wesmaelius (Kimminsia) subnebulosus, W. (K.) nervosus, W. (K.) malladai, and W. (K.) ravus, the only accurate way to identify the species is looking at either the male genitalia or the female anal plates (see below image).
