This species is mainly present in Austria, Belgium, Great Britain, Czech Republic, Finland, France, Germany, Greece, Hungary, Italy, Poland, Romania, Russia, Slovakia, Spain, Sweden, Switzerland, in the eastern Palearctic realm, and in the Near East.

Also the abdomen is strongly stretched, broader at the posterior end and placed on the upper chest (propodeum).

In resting position, these wasps slowly and rhythmically raise and lower the abdomen.

The adults grow up to 10–17 millimetres (0.39–0.67 in) long and can mostly be encountered from May through September feeding on Apiaceae species.

Gasteruption jaculator has been found visiting various flowers, or hovering around the nests of solitary bees and wasps in gardens and meadows.