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Iris Seed Weevil Mononychus punctum-album

The larvae of the Iris Seed Weevil lives in the seeds of the Yellow Iris, also known as Yellow Flag (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). In small numbers they do little damage, but may cause small holes in the buds of the flowers. So the flowers can look punctuated. When appearing in great numbers they may completely ruin an Iris, sometimes even causing the plant to die.

The adult beetle is some 4 to 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. Yet the species is easily identified by the white (sometimes yellow) spot near the beginning of the shields. Even though there is only one breed a year the little beetles live for a long time. The first adults appear in May, feeding and swarming. Mating takes place in May as well. In July females start to deposit their eggs in the developing seeds of the host plant. The larvae are very secure in the seeds, for Irisses will quickly fill all holes made by the beetle by producing a special liquid that fills up the holes. This liquid quickly hardens when in contact with air. The new adults appear in August and September, rapidly find a place in leaf litter and that is where they overwinter.

The Iris Seed Weevil comes in various variations: black with a white dot, brown with a yellow dot and slightly colourful (the Turkish variety) with either a white or a yellowish dot. In the past three species were distinguished: Mononychus punctumalbum, black, Mononychus pseudacori, brown and Mononychus salviae, the more colourful variety. Nowadays these are all considered to be just one species: Mononychus punctum-album. The scientific name is also written as Mononychus punctumalbum by the way.

The Iris Seed Weevil is also known as the Single-clawed Weevil.