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What they do with their heads...

Much of the variation among species involves modifications of the clypeus and mandibles, and results in different degrees of exposure of the labrum. An extreme development occurs in the alysiines, which have broad, non-overlapping, outwardly-directed mandibles, as exemplified in the leftmost image above. The rightmost two figures illustrate two different species with an exposed labrum, each with a slight differences in the configuration of the clypeus and the ventral-median rotation of the mandibles. Opiines differ from traditional cyclostomes in that the labrum is flat, rather than concave. In the 2nd figure from the left, the labrum is concealed, and the mandible is abruptly widened basally (producing a "basal tooth"). This is the condition found in the type species of Opius, O. pallipes Wesmael.