The left is a Large Rose sawfly. But the other sawfly is an other species. Perhaps an Iris Sawfly.
The Large Rose Sawfly saws a hole in a Rose (plant) and lays eggs

The larvae eat the rose. But usually there is not much damage,  because the larva has many natural enemies. 

In August I saw the larvae of the Large Rose Sawfly (Arge pagana) on the rose.

     

Arge cyanocrocea resembles the Arge pagana. But the difference is still clearly visible through the dark part of the wings.

The larvae feed on the leaves of blackberry, especially blackberries (Rubus fruticosus), raspberry (Rubus idaeus) and burnet (Sanguisorba officinalis) ..
Length: 7, 8 mm.
Europe, Asia Minor, Japan.

  Photos 21-5-2011, 22-5-2011

The light green larvae feed on the leaves of the strawberry. They can be found at the back of the leaves.
Two generations in a year. (spring and autumn) 
Length 6 - 9 mm.
They hibernate as a pupa in the soil.
It looks like the Allantus cingulatus, but in Allantus cingulatus the jaws in part and the labrum are usually white.
The Dutch name (translated) is strawberry sawfly. The English name shows, the larvae also like the leaves of roses.
Here you can read more about it.  http://www.sactorose.org/ipm/84rosesawflies.htm

  German: Rosensägewespe, Gebänderte Rosenblattwespe

Thanks José Luis Ruiz de la Cuesta

There are many similar species. And there are not many specialists, you can consult.
This black and red dolerus looks like a Dolerus Germanicus. But they have brown knees. 
I have read, that Dolerus bajulus and Dolerus aericeps are also similar. This saw flies flew from one grass blade to another and were therefore difficult to photograph.
You often see them in April and May

  Photos 11-4-2010 Another Dolerus spec.

A small black with red sawfly.
Length 7 mm.

There are many species Macrophya. The white bands around the legs are striking. But these bands have more species.
They are found near birches. But also near other deciduous trees such as Acer campestre. (food plants for larvae)

    Photos 15 -7-2011

These two species are recognizable by the white pronotum. According to Jorgen Ravoet you can see the difference between the species if you have a good view of the posterior trochanters. Thanks Jorgen.

  Photos 23-4-2011

The antennae are striking by the large segments.

It's a difficult subfamily. The species and even the genus can not be determined. Nematus is a possibility. But it is not certain. (For example, Willow sawfly - Nematus salicis. There are many photos of the larvae, but none of the sawfly itself.)

Photos 3-11-2007

Iris Sawfly (Rhadinoceraea micans) Family Common sawflies (Tenthredinidae).

There are other black similar species. Because they are found in the garden on the Yellow iris and because I had larvae of the iris sawfly,  I think this is the Iris Sawfly. The larvae can grow up to 5 cm long.
In June they move into the ground, spin under the ground a cocoon and pupate.
In May the sawflies appear, which deposit the eggs.

German: Irisblattwespe  French: Tenthrède des iris

Rhogogaster spec  Perhaps  a green sawfly (Rhogogaster viridis) Family Common sawflies (Tenthredinidae).

The larvae feed on the leaves of a wide range of plants and trees.  
The sawfly hunt on other insects and their larvae.

Figwort Sawfly (Tenthredo scrophulariae)  Family Common sawflies (Tenthredinidae).

Also this is a sawfly, although it looks like a social wasp. It has the same length (15 mm) of many wasps.  But there is no real waist.
The adult wasp hunts on other small insects. The larva eats plants of the figwort family. The antenna is orange.

German: Braunwurzblattwespe

  Photo 17-7-2011                Males and females Photo 28-7-2011

I noticed a real robber. Occasionally I see it with prey to the yarrow, where many flies are. See last picture.
About 13 mm.
The black body with the bright yellow stripes looks like the body of social wasps (Vespidae). The wings have a dark spot. The first segment of the black antenna is orange

  Photo 3-7-2011

Photos 10-7-2011