Gelis bicolor 
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The ichneumon wasp Gelis bicolor is a common wasp in the Netherlands .
The females can be found the whole year through and overwinter as adult .
The species develops in spider and is an idiobiontic ectoparasite . Normally one wasp develops per eggsack  and the larva will eat the entire contents .
3. FOOD PLANTS
The adults wasps feed on nectar and honeydew . 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 . Possibly pollen grains stuck on the sticky surfaces of hairy leaves are eaten as well .
In literature the following plants and groups are cited in the context of licking up food and moisture:
|– Corylus avellana (Common hazel) |
– Alnus alnobetula (Green alder) 
|– Urtica dioica (Stinging nettle) |
In the garden the following plants are present:
|– Corylus avellana (Common hazel)|
|– Urtica dioica (Stinging nettle)|
4. PARASITIC RELATIONS
The species parasitizes the eggsacks of spiders as food for the larvae [3,4].
The following prey groups and species occurring in the Netherlands  are cited in literature:
|Linyphiidae (Money spiders)|
– Floronia bucculenta 
Mimetidae (Pirate spiders)
– Ero cf. furcata 
Length: 2,2 – 4,0 mm
The genus Gelis can be recognized by the following characters:
1. 2nd and 3rd tergite fully separated, or only partially or unclearly merged 
2. 1st tergite with or without dorsal lateral carinae 
3. 1st tergite not or seldom apically striped 
4. If tergite 1 apically striped than laterotergite of 2nd abdominal segment separated  (Here not the case)
1. Head black 
2. Antennae with 20-22 segments 
3. Antennal segment 3 is 2,5-3,4x longer than wide (lateral view) 
3. Antennal segment 7 is 1,3-1,8x longer than wide (lateral view) 
4. Distance between hind ocelli ( OOL ) is about 0,7-1,0x the distance between the hind ocellus and the inner eye edge ( POL ) 
5. Clypeus under edge convex 
6. Genal groove deep 
7. Occipital carina connected with hypostomal carina at mandible base 
1. Thorax and propodeum usually orange, in smaller specimen black to brown 
2. Mesonotum without clear medial longitudinal furrow 
3. Mesonotum about 0,8-1,1x longer than wide 
4. Scutellum not clearly limited, very short 
5. Length mesonotum = 0,8-1,5x length area anterior 
6. Slope rear mesonotum and propodeum unequal 
7. Propodeum about as high as mesonotum 
8. Transverse carina on middle propodeum clear, straight not arched 
9. Thigh (femur) hind leg 3,3-4,1x longer than high hoog (lateral view) 
1. Tergite 1 with dorsal lateral carinae, partly 
2. Abdomen from tergite 2 black 
3. Abdomen densely haired 
4. Ovipositor tip with fine to clear teeth ventrally
References1 Nederlands Soortenregister
3 SCHWARZ, M. Revision der westpaläarktischen Arten der Gattungen Gelis THUNBERG mit apteren Weibchen und Thaumatogelis SCHMIEDEKNECHT (Hymenoptera, Ichneumonidae). Teil 2.
4 Finch, Oliver-David. (2005). The parasitoid complex and parasitoid-induced mortality of spiders (Araneae) in a Central European woodland. Journal of Natural History - J NATUR HIST. 39. 2339-2354. 10.1080/00222930500101720.
5 SCHWARZ, Martin. Revision der westpaläarktischen Arten der Gattungen Gelis Thunberg mit apteren Weibchen und Thaumatogelis Schmiedeknecht (Hymenoptera, Ichneumonidae). Teil 1. na, 1995.
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