Omocestus viridulus - Common Green Grasshopper
(L., 1758)

Description: Small species (♂ 13-17 mm, ♀ 20-24 mm). The ground colour can be very variable (green or yellowish brown, sometimes violet) , the ventral side is green, the labial palps are entirely light-coloured. The side keels of the pronotum are only slightly bent. The end of the abdomen is never red. Wings without any spots. In males the wings are slightly longer than the hind knee, in females they are shorter.
Similar species: Omocestus rufipes, Stenobothrus lineatus
Adults: from June to October.
Song:
Like the song of O. rufipesbut usually longer (20-40 sec.), resembling a rapid alarm clock, which can be heard from 20 m away. The song starts quietly, quickly increases in intensity and reaches its maximum volume long before it stops.

Source: Orthoptera Species File (lab recording))
Habitat:  Humid grasslands, marshes.
Distribution:
Rare and local, in mountains (e.g. Kőszegi-hg., Aggteleki-karszt).

Omocestus viridulus, male
(Author: Dobos Zsolt)

Omocestus viridulus, male
(Author: Gilles San Martin, source: flickr.com, CC BY-SA 2.0)