This genus has comprised hitherto some half-dozen North-American species, and three or four others from Eastern Asia. It is evidently destined to prove very numerous in species from tropical America, and it is doubtful whether the Old-World forms will be retained in the genus. The species are very difficult to describe and some exhibit much variation in colour, this being sometimes in part sexual. The prosternal structure is somewhat variable, but the apices of the epimera are always free; though I think I have observed in one species that one minutely overlaps the other, the apices in this case not being united but separated by a small space. A readily observed character for the recognition of the genus exists in the extremely peculiar club of the antennæ, which is always very long and fragile, but varies much in the form and proportion of the joints.
 
In addition to the series of species here described, I have evidence of the existence of eight or ten other species in our region, each of which is represented by a single example in too decayed condition for examination.