Wednesday, 9 May 2018

Dicyrtomidae Identification Guide

Members of the Dicyrtomidae are characterised by having a very short fourth antennal segment. Key identification features for each species are described below.

Family Dicyrtomidae
Genus Dicyrtoma
Dicyrtoma fusca

Genus Dicyrtomina
Dicyrtomina minuta
Dicyrtomina ornata
Dicyrtomina saundersi

Genus Jordanathrix
Jordanathrix nr superba



Dicyrtoma fusca is a small globular springtail (1-2mm) which varies considerably in colour from a dark maroon red to a paler yellow form, the mottled patterning also varies:

Dicyrtoma fusca

Dicyrtoma fusca

The above (commonest) forms are known as Dicyrtoma fusca var.1. There is also a much rarer melanistic dark (almost black) form, Dicyrtoma fusca var.2 (not known from VC55), and a leucistic form with dark ocelli on a pale eyepatch, Dicyrtoma fusca var. rufescens:

Dicyrtoma fusca var. rufescens

Dicyrtoma fusca var. rufescens




Dicyrtomina minuta
A common species found throughout Britain. The name is of this species is confusing - some D. minuta specimens grow bigger than D. ornata. Typically pale gold and less pigmented than D. ornata (dorso-anterior pigmentation lacking in particular). Similar to D. ornata, there is a long, narrow pigment streak on the rear of the abdomen. Facial interocular pigmentation:
In D. minuta there are 2 dark spots: one on top of the head and one just below the antennal bases.
In D. ornata these spots are interconnected by a brown stripe.

Dicyrtomina minuta



Dicyrtomina ornata
The historical records for a number of groups of springtail are hopelessly confused. These include Entomobrya intermedia/nivalis and also Dicyrtomina ornata/saundersi. This species has been frequently identified by the large rectangular patch of dark pigment on the abdomen, but this species is very variable in pattern and colour. Key features:
  • No sharp colour change along the length of the antennae
  • Dorsal colour of the 6th abdominal segment (the dorsal anal valve) is dark:

Dicyrtomina ornata

Dicyrtomina ornata

Dicyrtomina ornata


Dicyrtomina saundersi
Key features:
  • Distinct colour change at the joint of sections 2 and 3 of the antennae
  • Dorsal colour of the 6th abdominal segment (the dorsal anal valve) is light:

Dicyrtomina saundersi

Dicyrtomina saundersi


Jordanathrix nr. superba
This species resembles but is distinct from Dicyrtomina superba from New Zealand. Thought to be a relatively recent introduction to the UK, first recorded about 10 years ago. This species has a patch of dark pigment on the abdomen and is similar in appearance to D. ornata but the colour of the eyepatch is much paler (with dark ocelli) than the all-dark eyepatch of D. ornata:

Jordanathrix nr. superba

Jordanathrix nr. superba

Jordanathrix nr. superba - male




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