It is a diminutive low-wing monoplane of conventional if stubby appearance with a cruciform tail, an enclosed cabin and fixed, tricycle undercarriage.

Significant parts of the design were undertaken by students at the training college attached to the PZL plant at Okęcie under the direction of Andrzej Słocinski,[1] with the whole project treated initially as a platform for design innovation.

[3] Plans to fly a prototype by 1985 were delayed by revisions to the aircraft's equipment, although a mockup was displayed at an agricultural aviation exhibition at Olsztyn that August.

[3] Legislation to outlaw certain agricultural chemicals was under consideration in Poland in the late 1980s, spurring interest in biological agents as an alternative and making a tiny aircraft like the Mrówka feasible as a useful piece of agricultural equipment.

[4][5] After initial testing, the design was revised and the prototype rebuilt as the PZL-126P, flying in this configuration on 20 October 2000.