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]}

Table 3-1: Food plants in the Netherlands

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]}

Table 5-1: Parasitic species in the Netherlands

Parasitic species outside the Netherlands:

–

Table 5-2: 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]}

*Gelis bicolor* ♀︎, *Gelis*: tergites 2 and 3 fully separated

2. Abdomen: tergum 1 with or without dorsal lateral carinae ^{[Schwarz 1995]}

*Gelis bicolor* ♀︎, *Gelis*: tergum 1 with dorsal lateral carinae

3. Abdomen: tergum 1 not or seldom apically striped ^{[Schwarz 1995]}

*Gelis bicolor* ♀︎, *Gelis*: tergum 1 apically not striped

4. Abdomen: If tergite 1 apically striped than laterotergite of 2^nd abdominal segment separated^{[Schwarz 1995]}(Here not the case)

*Gelis bicolor* ♀︎, *Gelis*: laterotergite abdominalsegment 2 not separated from tergite

HEAD

1. Head black ^{[Schwarz 2002]}
2. Antenna: with 20-22 segments ^{[Schwarz 2002]}

*Gelis bicolor* ♀︎, antennae with 20-22 segments

3. Antenna: segment 3 is 2,5-3,4x longer than wide (lateral view) ^{[Schwarz 2002]}

*Gelis bicolor* ♀︎, antennal segment 3 is 2,5-3,4x longer (l) than wide (b) *(lateral view)* (here ±3x)

3. Antenna: segment 7 is 1,3-1,8x longer than wide (lateral view) ^{[Schwarz 2002]}

*Gelis bicolor* ♀︎, antennal segment 7 is 1,3-1,8x longer (l) than wide (b) *(lateral view)* (here ±1,8x)

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]}