Official name
Synonyms
Gelis bicolor [Soortenregister]
Ichneumon bicolor
zie meer op: www.gbif.org

CONTENTS
1. Distribution
2. Behaviour
3. Plant relations
4. Parasitic relations
5. Identification
1. DISTRIBUTION
The ichneumon wasp Gelis bicolor is a common wasp in the Netherlands [Waarneming.nl].
2. BEHAVIOUR
2.1. ACTIVITY
The females can be found the whole year through and overwinter as adult [Schwarz 1998].
2.2. DEVELOPMENT
The species develops in spider and is an idiobiontic ectoparasitoid [Schwarz 1998]. Normally one wasp develops per eggsack [Schwarz 1998] and the larva will eat the entire contents [Finch 2005].
3. FOOD PLANTS
The adults wasps feed on nectar and honeydew [Schwarz 1998]. Flower visits are limited to specific weather conditions, like during drizzle or muggy weather and is probably secondary to licking up honeydew and moist from leaves [Schwarz 1998]. Possibly pollen grains stuck on the sticky surfaces of hairy leaves are eaten as well [Schwarz 1998].
In literature the following plants and groups are cited in the context of licking up food and moisture:
Birch family (Betulaceae) | – Corylus avellana (Common hazel) [Schwarz 1998] – Alnus alnobetula (Green alder) [Schwarz 1998] |
Netle family (Urticaceae) | – Urtica dioica (Stinging nettle) [Schwarz 1998] |
4. PARASITIC RELATIONS
The species parasitizes the eggsacks of spiders as food for the larvae [Schwarz 1998],[Finch 2005].
The following prey groups and species occurring in the Netherlands [Soortenregister] are cited in literature:
Spiders (Araneae) | Dictynidae (Mesh-webbed spiders) Dictyna – Dictyna sp. [Schwarz & Shaw 1999] Linyphiidae (Money spiders) Floronia – Floronia bucculenta [Finch 2005] Mimetidae (Pirate spiders) Ero – Ero cf. furcata [Finch 2005] Theridiidae (Comb-footed spiders) Paidiscura – Kleine boskogelspin (Paidiscura pallens) [Schwarz & Shaw 1999] |
Parasitic species outside the Netherlands:
– | – |
5. IDENTIFICATION
Length: 2,2 – 4,0 mm
Females are apterous [Finch 2005].
Males are brachypterous or macropterous [Finch 2005].
Genus
The genus Gelis can be recognized by the following characters:
1. Abdomen: terga 2 and 3 fully separated, or only partially or unclearly merged [Schwarz 1995]
2. Abdomen: tergum 1 with or without dorsal lateral carinae [Schwarz 1995]
3. Abdomen: tergum 1 not or seldom apically striped [Schwarz 1995]
4. Abdomen: If tergite 1 apically striped than laterotergite of 2nd abdominal segment separated [Schwarz 1995] (Here not the case)


HEAD
1. Head black [Schwarz 2002]
2. Antenna: with 20-22 segments [Schwarz 2002]
3. Antenna: segment 3 is 2,5-3,4x longer than wide (lateral view) [Schwarz 2002]
3. Antenna: segment 7 is 1,3-1,8x longer than wide (lateral view) [Schwarz 2002]

4. Ocelli: distance between hind ocelli ( OOL ) is about 0,7-1,0x the distance between the hind ocellus and the inner eye edge ( POL ) [Schwarz 2002]

5. Clypeus: apical edge convex [Schwarz 2002]
6. Gena: genal groove deep [Schwarz 2002]
7. Occipital carina: connected with hypostomal carina at mandible base [Schwarz 2002]
THORAX
1. Thorax and propodeum usually orange, in smaller specimen black to brown [Schwarz 2002]
2. Mesonotum: without clear medial longitudinal furrow [Schwarz 2002]
3. Mesonotum: about 0,8-1,1x longer than wide [Schwarz 2002]
4. Scutellum: not clearly limited, very short [Schwarz 2002]
5. Mesonotum: length = 0,8-1,5x length area anterior [Schwarz 2002]
6. Slope rear mesonotum and propodeum unequal [Schwarz 2002]
7. Propodeum about as high as mesonotum [Schwarz 2002]
8. Propodeum: transverse carina on middle clear, straight not arched [Schwarz 2002]
9. Hind leg: thigh (femur) 3,3-4,1x longer than high hoog (lateral view) [Schwarz 2002]
ABDOMEN
1. Tergum 1: with dorsal lateral carinae, partly [Schwarz 2002]
2. Abdomen: from tergum 2 black [Schwarz 2002]
3. Abdomen: densely haired [Schwarz 2002]
4. Ovipositor: tip with fine to clear teeth ventrally [Schwarz 2002]

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Literature
Finch 2005 Finch, O. D., 2005. The parasitoid complex and parasitoid‐induced mortality of spiders (Araneae) in a Central European woodland. Journal of Natural History, 39(25), 2339-2354.Schwarz 1995 Schwarz M., 1995. Revision der westpaläarktischen Arten der Gattung Gelis THUNBERG mit apteren Weibchen und Thaumatogelis SCHIEDEKNECHT (Hymenoptera, Ichneumonidae). Teil 1. – Linzer biologische Beiträge – 0027_1: 5 - 105.
Schwarz 1998 Schwarz M., 1998. Revision der westpaläarktischen Arten der Gattungen Gelis THUNBERG mit apteren Weibchen und Thaumatogelis SCHMIEDEKNECHT (Hymenoptera, Ichneumonidae). Teil 2. – Linzer biologische Beiträge – 0030_2: 629 - 704.
Schwarz 2002 Schwarz M., 2002. Revision der westpaläarktischen Arten der Gattungen Gelis THUNBERG mit apteren Weibchen und Thaumatogelis SCHWARZ (Hymenoptera, Ichneumonidae). Teil 3 – Linzer biologische Beiträge – 0034_2: 1293 - 1392.
Schwarz & Shaw 1999 Schwarz M. & Shaw M., 1999. Western Palaearctic Cryptinae (Hymenoptera: Ichneumonidae) in the National Museums of Scotland, with nomenclatural changes, taxonomic notes, rearing records and special reference to the British check list. Part 2. Genus Gelis THUNBERG (Phygadeuontini: Gelina). – Entomologist's Gazette – 50(2): 117 - 142.
Soortenregister Nederlands Soortenregister
Waarneming.nl Waarneming.nl
Citation
Krischan, O.R., 2025. Gelis bicolor. Kerfdier, www.kerfdier.nl. Accessed on 21 June 2025.