Omocestus petraeus - Rock-dwelling Grasshopper
(Brisout, 1856)

Description: Very small (♂ 10-14 mm, ♀ 13-15 mm), brownish (sometimes greenish) species. The wings reach about to the hind knee. The top of the pronotum is about as long as the head, the side keels are angularly curved. The head is quite large in relation to the body.
Similar species: Omocestus haemorrhoidalis, Myrmeleotettix maculatus, Stenobothrus stigmaticus
Adults: from July to October
Song:
Males do not often sing, so it is difficult to find the species. The song consists of 8 to 20 consecutive syllables, starting softly and gradually increasing in intensity. The entire song lasts about 3-6 seconds.

Source: Orthoptera Species File (lab recording, 26 °C)
Habitat:  Typical species of dry alkaline grasslands. Prefers bare ground.
Distribution:
Widespread in lowlands and on warm hillsides.

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

Omocestus petraeus
(Author: Kiss Tamás, source: ízeltlábúak.hu, CC BY 4.0)