*subwelchi Denis, 1924
Xenylla welchi is a scarce bluish species which reaches 1.0 mm in length. All the records are from English cultivated mushroom beds, glasshouses (growing cucumbers), and compost heaps. Thus it may be an old introduction rather than a native member of our Collembola fauna. The mucro is separate from the dens and bears a prominent lamella (Figs. 1 and 2). The tenaculum has 3+3 teeth (Fig. 3). Another useful character is the presence of only one clavate tenant seta on the outer side of the tibiotarsus of the first leg (leg1) which has been seen in all the specimens examined so far (Fig. 4). Legs2 (Fig. 5) and legs3 have two clavate tenant setae in this position. This helps to distinguish it from the similar Xenylla mucronata which has two clavate tenant setae on the outer side of the tibiotarsus of leg1. Also, the positions of setae p1 and p2 on th2 differ between the species. In the NHML collection, there are several specimens labelled Xenylla mucronata but these are all Xenylla welchi and are mapped as such here. There are no definite records of Xenylla mucronata from Britain and Ireland.