Tuesday, 1 May 2018

Orchesella Identification Guide

The genus Orchesella is characterized by:
  • Body scales absent.
  • 6 antennal segments with ant1+2 both subdivided. However: one or both antennae may be reduced in length due to damage, and the first instars have only 4 antennal segments hence fail to key out.
  • Head with 7 + 7 or more eyes, postantennal organ absent.

There are five species on the UK checklist but only two are commonly encountered:

Orchesella cincta "Belted Springtail"
One of the commonest springtails in Britain, reaching ~4mm. Key feature: dorsal surface of abd3 fully pigmented (this can be important in preserved specimens).

Orchesella cincta

Juvenile (<6 antennal segments):
Orchesella cincta juvenile

Orchesella villosa "Shaggy Springtail"
Common and widespread, one of the largest springtails reaching ~5mm length. Pigmentation patterns on the body in patches and are variable but ant2-ant4 mostly dark(c.f. O. cincta). Long, backward curved macrosetae on abdomen (although these can be lost):
Orchesella villosa

Bald specimen:
Orchesella villosa

Orange/yellow "knees":
Orchesella villosa

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