Juveniles are usually green, adults more dark blue. Two pairs of manubrial teeth, but can only reliably be identified by examination of setae on the dens - I. caerulea has a larger macroseta on the outside of the 2nd pair up the manubrium, while I. anglicana has the inner of these 2 macrosetae larger than the outer and I. caerulea has 2 basal dorsal setae on the dens, I. anglicana has 3.

Damp places. 

Autumn-spring

True status in Britain is unknown, the species appears to be under-recorded due to identification confusion. 

Status in Leicestershire and Rutland not known.

https://www.collembola.org/publicat/isotoma.pdf