The adult Iris Seed Weevil (Mononychus punctumalbum) is some 4-5 mm long and looks like many other small weevils. 
The basic colour is black, but the shields may be covered in dense, short brown hairs. 
The species is easily identified by the white (sometimes yellow) spot near the beginning of the shields. 
With the exception of Scandinavia this species occurs throughout Europe.
The larvae of the Iris Seed Weevil lives in the seeds of the Yellow Iris (Iris pseudacorus).
The adults are seen on other plants as well, but usually on relatives of the Yellow Iris, such as the German Iris (Iris germanica) and the Bearded Iris (Iris barbatus). 

Hortobágy-Halastó, Hortobágy National Park, Hungary, 2 May 2019