Hymenoptera. The bees, bumblebees, ants, wasps and saw flies belong to that order.

Hymenoptera is divided into different subordes. Namely suborder Symphyta (This group has no waist, sawflies) and suborder Apocrita. Apocrita is also divided into two groups. Namely: Parasitica and Aculeta.

Parasitica: wasps or parasitic hymenoptera. The females have an ovipositor, with the ovipositor they lay eggs into or near larvae. These larvae are eaten by the wasp larvae. There are several families.
The largest group are the ichneumon wasp (Ichneumonidae). Other groups are: Braconidae, chalcid wasps (Chalcidoidea), Gasteruptiidae, gall wasps (Cynipoidea) The plant galls develop, when the eggs are laid.  

Aculeata: In this group the ovipositor is is modified into an stinger. With this stinger they can defend themselves (bees) or they can stun a prey.  In this group are also wasps with parasitic larvae. Spider wasps look like ichneumon wasps, but have a sting to stun their hosts. Jewel wasps (Chrysididae) have a sting too.

Ichneumon wasps, Ichneumonidae

There are many species in the world. (60.000 species worldwide) Ichneumon wasps are parasitoids of other insects.  Their abdomen is  very elongated and have long antennae (at least 16 segments)
They are solitary. There are many subfamilies. 

On Lady's Mantle. Photo 14-5-'11

On the trunk of a dead apple tree. This is not without danger, because there also lives a Marpissa muscosa  (a large jumping spider). Photos 12-6-2011

About 10 mm. Photo: 22-7-2012

Gergely:  To my opinion, it is a Casinaria or something closely related in Campopleginae...     Photos 5-11-2011.

Photos 2-6-2012.

Looks like a female Stenarella sp., domator or closely related. I have specimens from Finland with and without a white ring on the antennae...  Gergely Várkonyi

Stenarella domator on internet don't have white rings on the antenna. Thanks Gergely.

Photos 4-6-2011

A black wasp with orange legs. Cream: scutellum, line along the side of the thorax, the eyes and antennae and bands on the shins of the hind legs. On the shins of the hind legs are also black bands. The lower part of the rear legs is black.
Length about 7 mm.
April - October.

Diplazon laetatorius lays eggs in the larvae of hoverflies.

Photos 4-9-2012

They are small and mobile. You must be lucky, to get a good photo. I always see them in spring. 

Photos 20-4-2008

About 15 mm.

June - September.

Photos: 23-11-2009.

Photo: 25-8-2015.

Photo 11-9-2010.

Photo 28-9-2014.

Photos 11- 9-2010

Comments Camille Thirion: 6-8 mm possible Cratichneumon culex female
7-10 mm Cratichneumon nigritarius or fabricator. Thanks Camille.

  Photos 14-5-2011

    Photos 26-4-2011 (Male)

About 18 mm.

Photos: 13-8-2013.

Patrocloides sputator. Tribe Ichneumonini. Subfamily Ichneumoninae. Family Ichneumon wasps, Ichneumonidae.

Black with red shins and a red band around the abdomen. 

Photos 19-10-2012. female.

Stenichneumon culpator. Tribe Ichneumonini. Subfamily Ichneumoninae. Family Ichneumon wasps, Ichneumonidae. 
Difficult for it is very simiilar to the Patrocloides sputator. 

Black with red shins and a red band around the abdomen. 
According to Camille Thirion the abdomen end is that of Stenichneumon!: Abdomen end of Patrocloides sputator = Amblypygi.
Head narrowed behind at Stenicheumon culpator. 
Very strong spine of coxa III in the medium of the coxa female culpator. (coxa III is the first segment of the hind leg near the body).
The spine of the coxa isn't visible in these photos. Here the link to my question on the forum Hymis. 

Photos 25-3-2014. Female.

Vulgichneumon F saturatorius nigripedis. Tribe Ichneumonini. Subfamily Ichneumoninae. Family Ichneumon wasps, Ichneumonidae.

The similar Vulgichneumon saturatorius and Vulgichneumon bimaculatus have red legs.
The size of this Ichneumon wasp is about 11, 12 mm. 

      Photos 4-9-2012.

Colpotrochia cincta. Subfamily Metopiinae. Family Ichneumon wasps, Ichneumonidae.

A black ichneumon was. The abdomen and legs have pale yellow bands. After one photo it disappeared.
The size of this Ichneumon wasp is about 11 mm. 
June - August.

Photo 18-8-2013.

Enicospilus spec. Tribe Enicospilini. Subfamily Ophioninae. Family Ichneumon wasps, Ichneumonidae.

In the Netherlands, there are six species: E. combustus, E. merdarius, E. ramidulus, E. repentinus, E. tournieri, E. undulatus.
Deze wesp was ongeveer 2 cm. 

  Enicospilus genus is distinguished by the two orange spots on the wings (indicated by two arrows). 

Photos 24-8-2016.    

Ophion minutus. Tribe Ophionini. Subfamily Ophioninae. Family Ichneumon wasps, Ichneumonidae.

Not sure, because there are more similar species. However, this species is active this time. Furthermore, they can also be confused with Netelia species. However, the wing veins of these wasps is different. 
This is a relatively small species. I also see larger species, but they don't want to sit still up till now. A light orange Ichneumon wasp with yellow markings on the thorax. Male, because the females have an ovipositor.
Host: caterpillars.
Length about 11 - 15 mm. April - June.

Photos 24-4-2014.

Apechthis compunctor Subfamily Pimplinae. Family Ichneumon wasps, Ichneumonidae.

An ichneumon wasp of the genus genus Pimplinae. I am glad it was possible to determine this species.
Length: 7 - 15 mm. June - October.  Photos 4-9-2010, 3-10-2013.   

A small one. A bit smaller than 1 cm. 
Photo 26-9-2010.

A possibility is Pimpla rufipes. But there are more similar species. A black wasp with distinctive red legs. The antennae are black. Length about 15 mm. Photo 27-8-2013.

Gergely Várkonyi: This wasp belongs to the Polysphincta group of genera in Ephialtini (Pimplinae). Possible genera are (e.g.) Polysphincta and Oxyrrhexis. O. carbonator is one of the possibilities. But Polysphincta spp. look similar. (spp: species pluralis, several species). Thanks Gergely.  About 10 mm. Photos 15-10-2011

A slender Ichneumon wasp. A name isn't possible. Photos 2-10-2013.

Clistopyga spec. Tribe Ephialtini (Pimplinae). Family Ichneumon wasps, Ichneumonidae.

A slender Ichneumon wasp of about 7-8 mm. There are three known species in the Netherlands: Clistopyga incitator, Clistopyga sziladyi, Clistopyga sziladyi. Photos 24-5-2014.

Netelia spec. Tribe Phytodietini. Subfamily Tryphoninae. Family Ichneumon wasps, Ichneumonidae.

No Netelia testaceus, for the end of the body of this species is black. The other species are difficult to identify.

Furthermore, they can also be confused with ophion species. But the veins of  the wings are different.

  Photos 13-10-2008.

Many members of this family are parasites of the sawfly.

Photos 27-4-09

Photos 28-8-2011, 30-8-2011

On forum "hymis":
Henrik Gyurkovics thinks: It could be fam. Ichneumnidae, subfam.Cryptinae, and there is a remote possibility that it is some Gelis spec.

Thanks Henrik

Wasp in the genus Gelis are wingless.

A male. About 3 - 4 mm.

Wasp in the genus Gelis are wingless. Photo 20-10-2014.

A beautiful coloured wasp. About 5 mm.

  Photos 20-6-2016.

It was sitting in the shade. But I think it's still a nice photo. Black with red abdomen (not clearly visible on this photo) and red thighs. Antennae black with white. The ovipositor is bent downwards at the end. 
They feed on the larvae of some species of longhorn beetles. 
Approximately 16 mm.

May - June.

Photos 30-6-2012.

Gergely: This is a difficult one, Ctenopelmatinae/Tryphoninae...

About 1 cm. Very late in the year. Even the subfamily is not possible.

  Photos 13-11-2011

Braconidae

Wereldwijd is dit ook een heel grote groep met meer dan 10.000 soorten. Antennes hebben 17 of meer segmenten. Een slank lichaam.  

Ceraphronidae and Megaspilidae.
Ceraphronidae Megaspilidae and are both small families, which are closely related. The wasps can be brachypterous or wingless. The Megaspilidae with wings differ from the Ceraphronidae by a very large stigma in the wing. The larvae are parasites of all kinds of insects. All species are small (up to five mm).

Wingless, very small and dark. It struck me as he walked on a white stool. The wingless species are found in the soil between the leaf litter.

About 2 mm.

Photo 9-10-2012.  

The species is unknown. If you enlarge the pictures, you can see the clearly visible large stigma in the wing.
Small and dark on a bamboo leaf.

About 2 mm.

Photos 2-10-2012.  

Chalcid wasps, superfamily Chalcidoidea

There are many species. Most are small and therefore very difficult to identify from a photograph. The larvae parasitize.

A 3 or 4 mm wasp, with a beautiful golden glow. A name isn't possible.

   Photos 26-4-2011

A 3 or 4 mm wasp. Metallic, but different in colour than my other chalid wasp.
The front and rear tarsus consists of five segments. Length: 1 to 5 mm. Antenna: 8 to 13 segments. Few veins in the wing.

   Photos 10-7-2011

An approximately 3 mm long wasp with a blue-green sheen. A name isn't possible.
Most of Eulophidae are primary parasitoids of concealed larvae, like the larvae inhabiting leaf mines.

Photo 8-4-2014.

3 mm. I found it in the pantry. Below I have a picture, it was in a cup. After this photo I have put it outside and have taken more photographs. Metallic and as beautiful as a jewel wasp. 
Albert de Wilde told me that there are 11 species in the Netherlands.

    Photos 25-9-2011

Gall wasps, Cynipidae.

Most females in this group lay their eggs with their ovipositor in plants. Than the plant galls develop. Ibalia leucospoides, described below, does not lay their eggs on plants.

It is a parasite of wood wasps of the genera Sirex, Urocerus and Xeris which live in 'pine'.
A very special wasp. The abdomen is very narrow. It has the wings along its abdomen. The veins look very different to the veins of other wasps. Antenna female: 13 segments. Male 15 segments.
In the Netherlands there are known are two species: Ibalia leucospoides (Hochenwarth, 1785) and Ibalia rufipes Cresson, 1879. Worldwide there are not too many species.
Length to 15 mm.
Holarctic region; introduced to Australia, New Zealand and South Africa

   Photos 3-8-2011

Gasteruptiidae.

Characteristic of this family is that the metasoma (the posterior part of the body) is very high attached.  
The eggs are laid in nests of solitary bees. Antenna segments 13 (males) ​​or 14 (females) The hind tibiae are swollen and there are 3 red bands on the abdomen.

Probably  Gasteruption assectator. Family Gasteruptiidae.

The female has a short ovipositor. Similar to the larger Gasteruption jaculator. But the female has a long ovipositor. However, there are more species in the Netherlands.

Length 8 - 12 mm.

Two other species.    Photos 27-6-2011 and 4-7-2011