Field of Science

Raffrayia

In previous posts, I have introduced you to various representatives of the Pselaphinae, bizarre-looking little gorgon-headed beetles dwelling in soil. But as with all elements of the world's biodiversity, I have not even begun to scratch the surface of what this group has to offer. So for today, a post on another pselaphine genus: the African Raffrayia.

Male Raffrayia dilatata, from Jeannel (1955).


The genus Raffrayia was first established by Reitter in 1881 for a species found in Ethiopia and since then over twenty species have been recognised. The great majority of these have been from southern Africa, in particular from various locations in the Cape Province. Only the meerest handful have been described from scattered localities in east Africa. Nevertheless, it would not be at all surprising if this disparity between regions turns out to be in part an artefact of study effort; there may be more species yet to be described.

The most distinctive feature of the genus is one or two rings each of small button-like nodules on the median segments of the antenna (I am unable to guess the functional significance of these, if any). Jeannel (1955) recognised a number of smaller genera closely related to Raffrayia that share these antennal nodules but differ in having a more elongate basal segment on the abdomen and/or being uniformly flightless forms with the humeri ('shoulders') of the elytra reduced (flightless Raffrayia [see below] retain more distinctly pronounced humeri). Both of these features are derived and these segregate genera may well be expected to be derivatives of Raffrayia. Jeannel also distinguished two subgenera Raffrayia sensu stricto and Raffrayola based on the structure of the first abdominal segment. Raffrayola is restricted to southern Africa whereas Raffrayia sensu stricto is found across the genus' range.

Sexual dimorphism within the genus is strong: males are winged but females are flightless. Elytra are somewhat reduced in females as a result (but again, not as much as in consistently flightless genera). Unfortunately, while we can make some obvious inferences from this about their relative life styles, there seems to be little in the way of direct observations on how Raffrayia spend their lives.

REFERENCE

Jeannel, R. 1955. Les psélaphides de l'Afrique australe. Mémoires du Muséum National d'Histoire Naturelle, nouvelle série, Série A, Zoologie 9: 1–196.

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