COLEOPTERA > POLYPHAGA > CHRYSOMELOIDEA > Chrysomelidae > Criocerinae

Criocerinae is a small subfamily with just seven listed species, which have a distinctive elongate form with a thorax that's always narrower than the elytral shoulders. They are shiny or metallic, and with two species, Lilioceris lilii (Lily Beetle) and Crioceris asparagi (Asparagus Beetle) being particularly colourful.

There are three superficially similar species with dark metallic blue elytra, Oulema erichsoni, Oulema obscura and Lema cyanella and, whilst Oulema erichsoni is very scarce with only a few modern records from North Somerset, the other two species are common and widespread and can be easily confused without careful examination.

The two cereal leaf beetles, Oulema melanopus and Oulema rufocyanea, are unmistakable in outward appearance, but are impossible to separate without dissection and careful examination of the genitalia. With two specimens' side by side, Oulema rufocyanea is on average very slightly smaller and narrower, but even then, there is no certainty as individuals vary in size and the differences are so small. In most cases, Oulema melanopus is noted as the likely species when captioning photos.

Oulema melanopus is strongly associated with cereal crops, especially wheat, oats and barley, but may also occur where rye or maize is growing or in areas where there are wild grasses. Adults commence feeding early in the year, peaking in May and June, and again in August when they feed heavily prior to overwintering, which is typically from mid/late September though to the following April. Females lay their eggs on the underside of the leaves. The larvae hatch a few days later and start feeding voraciously on the upper layers of the leaves thereby stunting the plants growth.

Updated, Oct.22 (v.2)