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: In Europe three distinct species are currently recognized: D. minuta, D. ornata and D. saundersi. In the USA, these are lumped into one species, D. minuta with the variants as subspecies forms:
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.

Dicyrtomina minuta

Frans Jannsens says that a diagnostic character to distinguish D. minuta from pale D. ornata is the colouration of the interocular+interantennal area:
D. ornata: a distinct midfacial pigmented band.
D. minuta: this band indistinct to absent (often only 2 pigmented dots remaining, 1 interocular + 1 interantennal):

Dodgy Dicyrtomina


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. Pale juvenile specimens (<1.5mm) are difficult to separate from D. minuta (see above). Key features:
  • Dorsal (in addition to lateral) abdominal pigmentation
  • No sharp colour change along the length of the antennae
  • Dorsal colour of the 6th abdominal segment (the dorsal anal valve) is dark (c.f. Dicyrtomina saundersi, below):

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

No comments:

Post a Comment

Comments welcome, I will respond as soon as I can.