Desoria - covered in short setae (hairs); simple (unforked) setae by the feet.
Isotoma - long setae on all body segments.
Isotomurus - long setae on abd5+6 only.
Desoria infuscata - very rare, upland sphagnum bogs.
Desoria tigrina - common, widespread. Dorsal plus lateral pigment stripes. Macrosetae on abd5 <0.7 length of adb5. (All UK literature records for 'Isotoma olivacea' are probably Desoria tigrina.)
Desoria trispinata - probable horticultural import. No macrosetae on abd. Looks like Vertagopus arboreus but with blue rather than pale legs.
Desoria violacea - common, widespread. Dark colour with blue/violet iridescence. Macrosetae on abd5 approximately same length of adb5.
"Desoria tigrina (formerly Isotoma tigrina) is widespread and common, with a tendency towards human-impacted soils or habitats rich in organic matter. Desoria tigrina is light to dark grey or brown (never white, dark blue or violet)." - Photo Marie Huskens:
Desoria trispinata - Photo Marie Huskens:
11.03.18 SK508071 ~1.5mm in Beech leaf litter:
I haven't formally recorded this specimen but I'm 95% sure it is Desoria tigrina (better dorsal shots needed to confirm):
mucro has four teeth but does not possess a lateral seta
Under unfavourable conditions, six prominent spines may develop on abd5