- Last updated on 1999.12.29 by Frans Janssens
Checklist of the Collembola: Aggregations of Hypogastrura ripperi Gisin, 1952 in Canada

Frans Janssens, Department of Biology, University of Antwerp (RUCA), Antwerp, B-2020, Belgium
Dan L. Johnson, Agriculture and Agri-Food Canada Research Centre, P.O. Box 3000, Lethbrigde, Alberta, Canada


Note: This preliminary version of the document is currently being revised. Results can change and conclusions can be rethought. It is recommended to not copy down, print or quote this text. To keep up to date, it is preferable to use a hyperlink in steadt.

This manuscript is a compilation of the cooperative communication between Dr Dan L. Johnson of the Agriculture and Agri-Food Canada Research Centre of Lethbridge, Canada and myself on the sudden appearance of small aggregations of a Hypogastrurid springtail in Lethbridge, Canada.



The specimens have been collected by Dr Dan L. Johnson in small numbers from May 19 to May 27, 1997 when they appeared in small masses, and since those dates they could be found easely in less aggregated densities by leaving a pan of water out overnight.
Masses were actually irregular films on the surface of wet straw at one site, dead grasscuttings at another site. The most were found at an outdoor dog kennel on the surface of wet straw mixed with small amounts of urine and food.

Vial 1 : 68 Collembola specimens in ethanol
Vial 2 : .. Collembola specimens in ethanol
Note : they were not 'fixed' : the transparant cuticula came loose from the body, as if each specimen was wrapped into a transparant plastic bag. Gisin's fixative 1 could have prevented this artefact.

Label :
Vial 1 :

Mar 26, 1997
Lethbridge, AB, Canada
Dan Johnson
Ceratophysella pseudarmata ?
Vial 2 :
Suspected Ceratophysella pseudarmata
D. Johnson, col
Mar 27-30, 1997
Lethbridge, Alberta, Canada

Preliminary observations

After one hour in Gisin's clearing medium 2 and using a stereo microscope at low magnification, the following observations could be made :

Based on Christiansen & Bellinger (1980), Ceratophysella cannot be confirmed : 'Nearctic Ceratophysella should have relatively large (never minute) anal spines'. Also Folsom's original description (1916) of Achorutes pseudarmatus specifies 'anal spines long'.

These preliminary observations indicate that it is not a Ceratophysella species.

Tentative identification

With a compound microscope at 100x, on the distal part of the anal segment (abdomen VI), two minute anal spines on papillae are clearly visible.
Fig.3. Anal spine 100x
Photograph Frans Janssens copyright © (1998)

The key of the Norwegian Collembola of Fjellberg (1980) leads straightforward to Hypogastrura vernalis :


  1. Furca not reaching second pair of legs when folded forwards.
  2. Mandibles with strong molar plate, easily seen in cleared specimens.
  3. Furca well developed, dens at least with 3 setae.
  4. Head with 8+8 eyes, dark species ==> Hypogastrura


  1. Empodium of normal size.
  2. Mucro usually long and slender. Tibiotarsi with one ore more knobbed tenent hairs. No protrusible sac on antennae. Body hairs usually short, anal spines short ==> Hypogastrura sensu stricto
  3. Tibiotarsi with only 1 knobbed tenent hair.
  4. Posterior side dens with distinct papillae, largest apically.
  5. Empodium with a small lamella.
  6. Mucro shorter [then manubrialis], with distinct tooth before apex ==> vernalis (Carl, 1901)
Empodium with small, narrow lamella.
Mucro with distinct tooth before apex.
1.2 mm. Dark bluish red. Anal spines short, stright. Often in large numbers in dry meadows close to sea.

Stach (1949) states about Neogastrura manubrialis : 'the limit between those segments [3rd and 4th antennal segments] sometimes indistinct'. What is certainly the case for this set of specimens. In fact, it is more or less valid for all Hypogastrura s.s. Also the fact that the antenna is thickest at the joint of the 3rd and 4th segment gives the impression (at lower magnification) that the 4th segment is fused with the 3rd. Stach (1949) notes on N. purpurescens dorso-lateral spotted lines. Those are clearly seen also in these specimens.

Tentative identification : Hypogastrura cf. vernalis (Carl, 1901)

Note that all characters apply to the blob specimens except that the specimens do not have knobbed tenent hairs... Therefore, the use of 'cf.'

Final identification

The acuminate tenent hair, together with the statement of Christiansen & Bellinger (1980) that there are 'no valid Nearctic records for Hypogastrura vernalis', and the fact that Hypogastrura vernalis is not listed in the checklist of Skidmore (1995) motivates a reidentification, this time based on the key of Gisin (1960).

After verifying Gisin's diagnosis of H.(H.) vernalis against some completely cleared specimens (gently heated on electrical heating plate in Gisin's clearing medium), the tentative identification has to be revised.

Following the key of the European Collembola of Gisin (1960) :

Hypogastrura (Hypogastrura)

  1. Alle Tibiotarsen met je höchstens 1 Keulenhaar.
  2. Dens mit 6-7 Borsten.
  3. Anal Dornen auf niedrigeren [then papillata] Papillen.
  4. Hautkörner auf der Hinterseite der Dentes gegen den Mucro hin stark an Grösse zunehmend, manchmaal zu Dornen vergrössert.
  5. Empodium nur mit kleiner Lamelle.
  6. [Rücken]Borsten glatt oder höchstens schwach rauh.
  7. Mucrospitze gerade oder mehr oder weniger hakenförmig.
    Fig.4. Mucro with broad lamella 100x
    Photograph Frans Janssens copyright © (1998)
  8. Mucro mehr oder weniger hakenförmig, kürzer, mit breitere Lamelle. Ant. I mit zusätzlicher Borste vor dem Borstenquirl.
  9. Tibiotarsus mit spitzem Spürhaar. Im PAO sind die beiden vorderen Höcker grösser als die hinteren und quer gestellt. ==> ripperi Gisin, 1952
- 1.5 mm. Grau-blau. Abd. V und VI dorsomedian mit stärkerer Hautkörnung. Ant. IV mit 3-4 äusseren und 2-3 inneren Riechhaaren. Klaue mit Innen-, ohne Seitenzahn. Tibiotarsus ohne Keulenhaar.
Ventraaltubus mit 4+4 Borsten (unveröff.). Tenaculum mit 4+4 Zähnen.

This identification is confirmed using the key of the Nearctic Collembola of Christiansen & Bellinger (1980). Both publications mention Neogastrura assimilis Stach 1949, nec Krausbauer 1898 as synomym of ripperi. Stach (1949) has a very detailed diagnosis of Neogastrura assimilis.

Final identification : Hypogastrura (Hypogastrura) ripperi Gisin, 1952

Location :Lethbridge, Albertha, Canada
Date :1997.03.26-30
Leg. :Dr Dan L. Johnson
Det. :Frans Janssens
Col. :Dr Dan L. Johnson

Photographs of cleared specimens were made with a Fuji dia positive film of 100 ASA, type day-light. Dr De Bruyn of the RUCA, Antwerp, Belgium was so kind to provide for the scanned JPEG images.

At least the following photographs are to be made to document the identification :



1 Gisin's fixative :
     95% ethanol750 ml
     ethyl ether250 ml
     glacial acetic acid30 ml
     40% formaldehyde3 ml

2 Gisin's clearing medium :
     lactic acid100 ml
     glycerol20 ml
     40% formaldehyde4 ml