Spilomena troglodytes ♂︎

Last update: 19 September 2021
SPECIES: Spilomena troglodytes
GENUS: SPILOMENA
FAMILY: Digger wasps (CRABRONIDAE)



OBSERVATION:
2021-VI-08

YEARS:
2021

MONTHS:
JanFebMarAprMayJunJulAugSepOctNovDec


Official name

Synonyms

Spilomena troglodytes [1]

Spilomena vagans

see more on: www.gbif.org

Etymology

troglodytes

Greek: cave-dweller

Spilomena troglodytes ♂︎

Contents

1. Distribution
2. Behaviour
3. Plant relations
4. Prey relations
5. Parasitic relations
6. Identification

1. DISTRIBUTION

Spilomena troglodytes is a rare wasp [2] occuring throughout the Netherlands [3,9] with an exception of the coastal provinces and the wadden islands [3]. It is the most common representative of the genus in the Netherlands [9].

2. BEHAVIOUR

2.1. ACTIVITY

The species is active from beginning of June to half September [3].

Males frequently can be found swarming around bushes and trees [3,12].

2.2. DEVELOPMENT

Nest

Females nest in existing cavities [3,4,5,9,12] in old wood [4,5,9,12], twigs [4] and abandoned beetle boreholes [9,12], with a preference [12] of those made by Anobium sp. (Anobiidae) [3,12] (Anobium rufipes [6], Microbregma emarginatum [6]). She will gnaw her own nest as wel in the marrow of plant stemms [3].

Existing boreholes are cleaned before use [3,12]. Gnawed corridors are about 4-12cm in length [5]. The corridors have a diameter of 1,1-1,2mm [5].

The broodcells are placed sequentially in a row within the nest cavity [3,5,12]. The broodcells are separated by a 1-2mm thick bulkhead made of wooddust [5]. Every cell contains 50-60 thrips [3,12].

The filled nest is closed with a woodpulp plug that is tamped using the abdomen [3,13]. The outermost layer is fortified by mixing the woodpulp with saliva that hardens as it dries [3] into a somewhat shiny disc [12].

Females find their nest using smell and as a result normally take a lot of time to find it after returning from the hunt, which is typical in the genus Spilomena [5,12]. They will scout around a large surface around the assumed nest position untill they smelled it out using the antennae [5]

Development time

The developmenttime of the relatively large (1,25 mm), weakly saussage-like bent [12] egg is unknown.

Gender development

The male and female broodcells are reandomly placed in the nest cavity [5]. There are more female than male cells which results in a surplus of female over males in a ratio of 2:1 [5].

2.3. BEE HOTEL

The males as well as the females can be found on bee hotels. Females use them to nest.
From my own observation of a male arriving early in the evening I suspect the males to use empty boreholes as resting place, see here.

2.4. MATING

Most Crabronidae females produce one generation per year [8].

2.5. HUNTING

The prey is transported using the mandibles [4,12].

3. PLANT RELATIONS

3.1. WOOD

The following wood types are mentioned in literature as medium for the wasp to built her nests in:

Aesculus (Horse chestnut)– Horse chestnut (Aesculus hippocastanum) [6]
Alnus (Elm) [3]
Betula (Birch) [3]
Carpinus (Hornbeam) [3]
Crataegus (Hawthorn) [3]
Picea (Spruce)– Norway spruce (Picea abies) [6]
Rubus (Breamble) [7]
Salix (Willow) [3]

Fence poles [3] or thatched roofs [12] may be used as well.

3.2. FOODPLANTS

Males feed with honeydew that is licked from leafs.
The following wood types are mentioned in literature as foodsources:


Apicaceae
(Umbellifers)
Peucedanum [5]

Foeniculum [5]

Angelica [5]
Angelica archangelica [5]

Garden species

In the garden Foeniculum vulgare is present but I have not observed the species on it.

4. PREY RELATIONS

The species uses mainly nymphs of thrips (Thysanoptera) for her brood [3,4,5,9,12]. Observations have been reported on the use of Psyllids (Psyllidae) nymphs [4] and the nymphs of Scale insects (Coccidae) and Aphids (Aphidoidea) [4].

The following species and group occuring in the Netherlands [1] are mentioned in literature:

Aphidoidea (Aphids) [4,5]
Coccidae (Scale insects) [4,5]
Psyllidae (Psyllids) [4]
Thysanoptera (Thrips) [4]

Garden species

At least Thrips and Aphids are present in the garden.

5. PARASITIC RELATIONS

The following species and group occuring in the Netherlands [1, 2(Oscinella nigerrima)] are mentioned in literature:

Hymenoptera
(Wasps)
Ichneumonidae (Ichneumon wasps)

Neorhacodes
Neorhacodes enslini [3,10,12]


Chalcidoidea (Chalcid wasps)

Torymidae

Torumus
Torymus armatus [3] (als Diomorus armatus)
Diptera
(Flies)
Chloropidae (Frit flies)

Oscinella
Oscinella nigerrima [4]

6. IDENTIFICATION

Length males: 2 – 3 mm
Length females: 2,5 – 3 mm

Genus

The genus Spilomena can be identified using the following characters:

1.  Forewing: with two submarginal cells [9,10,11]

Spilomena troglodytes ♂︎, Spilomena: front wing with two submarginal cells

2. Forewing: submarginal cell 2 not petiolate [9,10,11]

Spilomena troglodytes ♂︎, Spilomena: second submarginal cel not petiolate

3. Forewing: pterostigma large and almost semicircular [9,10,11]

Spilomena troglodytes ♂︎, Spilomena: front wing with large, almost semi-circular pterostigma

4. Forewing: radial cell longer than pterostigma [9,10,11]

Spilomena troglodytes ♂︎, Spilomena: front wing; length stigma shorter than length radial cell

5. Forewing: radial cell tip sharp [9,10,11]

Spilomena troglodytes ♂︎, Spilomena: front wing radial cell pointed

6. Forewing: with one discoidal cell [9,10,11]

Spilomena troglodytes ♂︎, Spilomena: front wing with one discoidal cell

7. Abdomen: firrst abdominal segment not petiolate [9,10,11]

Spilomena troglodytes ♂︎, Spilomena: first abdominal segment not petiolate

8. Abdomen: entirely black [9,10,11]

Spilomena troglodytes ♂︎, abdomen entirely black




  1. Antenna with 12 segments [9,10,11]

2. Abdomen with 6 segments [9,10,11]

HEAD

1. Clypeus evenly rounded [10]

2. Mandible usually light brown, seldom dark brown [10]

3. Ratio distance between hind ocelli (POL) : distance hind ocella to eye edge (OOL) = 1,4 – 2,0 [10,11]

4. Back head less strongly developed [10]

THORAX

1. Frontal scutellem furrow narrow and without transverse carinae [10,11]

2. Apical edge mesonotum without longitudinal grooves [10]

3. Wing veins brown [10]

4. Dorsal field propodeum not limited by carina, at least at the base with net-like wrinkles between the main sculpture [10]

ABDOME

  1. Tergite 6 with double longitidunal carina [10]



specimen caught for identification on 10-vi-2021, length ±3mm

Spilomena troglodytes ♂︎
Spilomena troglodytes ♂︎
Spilomena troglodytes ♂︎
Spilomena troglodytes ♂︎
Spilomena troglodytes ♂︎, propodeum
Spilomena troglodytes ♂︎, propodeum


  1. Antenna with 13 segments [9,10,11]
Spilomena troglodytes ♂︎, antenna with 13 segments

2. Abdomen with 7 segments [9,10,11]

Spilomena troglodytes ♂︎, abdomen with seven segments

3. Face and clypeus yellow, at least the front edge yellow (here face and clypeus) [9,10,11]

Spilomena troglodytes ♂︎, face (F) and clypeus (C) with yellow markings

HEAD

1. Frontal edge clypeus not or lightly indented (here lightly indented) [10,11]

Spilomena troglodytes ♂︎, front edge clypeus lightly indented

2. Mandible distally with small red-brown spot [10,11]

Spilomena troglodytes ♂︎, mandibel distally with narrow red brown band

3. Clypeus entirely or almost entirely yellow [9,10]

Spilomena troglodytes ♂︎, clypeus entirely or almost entirely yellow

4. Ratio distance between hind ocelli (POL) : distance hind ocelle to inner eye edge (OOL) = 1,4 – 2,0 (here ±1,4) [10,11]

Spilomena troglodytes ♂︎, ool = 1,4-2,0x pol

5. Antennal members clearly restricted, bead-like [9,10,11]

6. Antennal flag dark, at most more or less red-brown on the inside [9]

Spilomena troglodytes ♂︎, antennae bead-like restricted

THORAX

1. Frontal scutellem furrow narrow and without transverse carinae [10,11]

Spilomena troglodytes ♂︎, frontal scutellem furrow narrow, without transverse carina

2. Dorsal field propodeum not limited by carina [9,10,11], at least at base with fine net-like wrinkles between the main sculpture [10]

Spilomena troglodytes ♂︎, dorsal field propodeum not limited by carina, at least at base with fine net-shaped wrinkles between the main sculpture

ABDOMEN

no specific characters



References

1 Nederlands Soortenregister

2 Waarneming.nl

3 Peeters, T.M.J., C. van Achterberg, W.R.B. Heitmans, W.F. Klein, V. Lefeber, A.J. van Loon, A.A. Mabelis, H. Nieuwen-huijsen, M. Reemer, J. de Rond, J. Smit, H.H.W. Velthuis, 2004. De wespen en mieren van Nederland (Hymenoptera: Aculeata). – Nederlandse Fauna 6. Nationaal Natuurhistorisch Museum Naturalis, Leiden, knnv Uitgeverij, Utrecht & European Invertebrate Survey – Nederland, Leiden.

4 BOHART, Richard M.; BOHART, Richard Mitchell; MENKE, Arnold S. Sphecid wasps of the world: a generic revision. Univ of California Press, 1976.

5 Koch, F. (2002), Blösch, M. (2000). Die Grabwespen Deutschlands – Lebens‐weise, Verhalten, Verbreitung. 71. Teil. In Dahl, F.: Die Tierwelt Deutschlands. Begr.: 1925. – Keltern (Goecke & Evers). – 480 S. 341 Farbfotos. ISBN 3‐931374‐26‐2 (hardcover). DM 98,–. Zool. Reihe, 78: 353-353. https://doi.org/10.1002/mmnz.20020780208

6 Vikberg, Veli. (2000). A re-evaluation of five European species of Spilomena with a key to European species and relevance to the fauna of North Europe, especially Finland (Hymenoptera : Pemphredonidae). Entomologica Fennica. 11. 35-55. 10.33338/ef.84044.

7 VAN LITH, J. P. De Nederlandse Spilomena-soorten (Hym. Sphecidae). Entomologische Berichten, 1955, 15.24: 525-527.

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