Egidyella arcana Beal and Zhantiev

R. S. Beal, Jr. & Zhantiev, R. D., 2001, A New California Species Of Egidyella Reitter (Coleoptera: Dermestidae), A Genus Previously Unknown In The New World, The Coleopterists Bulletin 55 (1), pp. 70-74 : 71-73

Egidyella arcana Beal and Zhantiev , new species

Description. Integument of dorsal and ventral surfaces light tan; dorsal and ventral surfaces densely clothed with recumbent, pale­golden setae. Head with fronto­clypeal region reflexed posteriad at about 908 angle at level of antennal base ( Fig. 2 ). Antenna 11­segmented with 7­segmented club ( Fig. 4 ) and extending in repose about to basal 1/5 of mesosternum. Ocellus distinct. Compound eye not projecting strongly from side of head; ratio of interocular distance to total width of head across eyes 1:1.5. Scutellum visible, about ½ as long as length of antennal segment 10. Elytra diverge slightly near apex. Prosternum and elytra with long setae inserted on lateral margins with longest setae 0.25 mm in length. Prosternum reduced; lateral process in front of front coxa about as wide as segment 3 of antenna; prosternal process narrow becoming razor­thin between front coxae. Front coxae prominent and nearly contiguous at apices; ratio of length of coxa to femur 1:1.55; ratio of length of femur to tibia (exclusive of spines) 1:0.93; femur 2.25 times as long as wide; spines on dorsal margin and at apex of tibia stout. Hind coxae contiguous; coxa terminating at lateral margin of metasternum and not meeting epimeron; configuration of hind coxa as illustrated ( Fig. 3 ). Abdominal sternum 1 (morphological sternum 3) relatively short so that posterior margin about level with posterior margin of hind coxa and not visible from below ( Fig. 2 ). Abdomen with 7 sterna externally visible. Phallus as illustrated ( Fig. 5 ).

Length from head to apex of elytra: 3.2 mm (length of only pronotum and elytra combined: 3.05 mm); width: 1.5 mm.

Types. Holotype and 1 paratype: Kern Co., CA: Hwy. 14 and Hwy. 178 [10 km west of Ridgecrest]. Taken in antifreeze pitfall trap V­30 to IX­5–79 ( Gilbert and Poore) . Holotype deposited in collection of the California Academy of Sciences; paratype deposited in California State Collection of Arthropods, Plant Pest Diagnostics Center , State of California Deptartment of Food and Agriculture .

Diagnosis. As distinct from E. prophetea , the antennal club of E. arcana consists of 7 rather than 6 segments; the fronto­clypeal region of the head is strongly reflexed rather than gently rounding from the plane of the frons; the ocellus is distinct rather than evanescent; the eyes do not project so strongly from the side of the head, and the interocular distance between the eyes is relatively greater; the scutellum is visible; the humeri are less prominent; the elytra extend as far as the posterior margin of visible abdominal sternum 6 rather than only as far as the middle of visible abdominal sternum 4; the elytra diverge only slightly rather than conspicuously; the posterior margin of the hind coxa is inflected rather than straight. The hind wings of E. prophetea are not folded in repose and extend beyond the end of the eltyra. The hind wings of E. arcana appear to be folded, but this has not been determined with certainty.

Etymology. The specific epithet arcana is a Latin feminine adjective meaning ‘‘secret’’ or ‘‘hidden,’’ a reference to the rarity of the species and its seemingly secretive habitat.

Biology. No information on the habitat is available other than that the pitfall trap in which the specimens were taken had been placed adjacent to a sand dune. E. prophetea is closely associated with a sand dune habitat, and this may be true of E. arcana . Males of E. prophetea have also been taken at lights. Females of neither species have been discovered and possibly are flightless. Flightlessness is not unknown within the family, the most familiar example being that of larviform females of Thylodrias contractus Motschulsky. One of us (RDZ) collected a larva of E. prophetea , which apparently was feeding on dead insects accumulated in the trough of a sand dune.

Relationships. Egidyella clearly belongs to the Dermestidae , tribe Attagenini . The presence of pentamerous tarsi, a median ocellus, clubbed antennae, and hind coxae grooved for the reception of the femora identify it as a dermestid. The larva (undescribed) in its general facies is typical of the Attagenini . Identifying adults as belonging to the Attagenini would not follow from the definition of the tribe given by Beal (1970).

The following combination of adult characters redefine the Attagenini so that it includes Egidyella : body covered with recumbent to suberect hairs, not scales; head partially visible from above; head with median ocellus distinct or evanescent; antennal club of 3 to 7 segments; anterior face of prosternum not covering gula and mentum when head in repose; pronotum without distinct sublateral carina on each side; hypomeron not forming distinct cavity for reception of antenna and not margined behind; prosternal process long and narrow; mesosternum not or not completely divided with hind margin visible for entire width; segment 1 of the tarsi short, less than ½ the length of segment 2. This definition recognizes that unlike E. arcana the ocellus may be evanescent, as in E. prophetea , and increases the possible number of segments in the antennae of members of the tribe. Beal (1970) defined the tribe as having an antennal club of three segments.

Egidyella is redefined by the following combination of characters: antenna 11­segmented with club of 6 or 7 segments; front coxae prominent; hind coxa not reaching metasternal epimeron; abdomen with 7 externally visible sterna; phallus with ventral bridge near base. It is possible that additional specimens of E. arcana are present in U.S. collections but remain unidentified. Since there are seven visible abdominal sterna, an antennal club with seven segments, and the front coxae are prominent, the species will not key out to the correct family in the keys of Brues, Melander, and Carpenter (1954), Arnett (1960), Borror, Triplehorn, and Johnson (1989), or other keys to U. S. Coleoptera with which the authors are acquainted. These features along with the presence of a median ocellus and a hind coxa grooved for the reception of the femur will, however, readily distinguish the species from other known Nearctic Coleoptera .

Discussion. Given their unique similarities, it is less likely that E. prophetea and E. arcana originated from separate lineages through convergence than that they had a common ancestor distinct from other Attagenini . In view of their adaptation to sand dune habitats and seemingly limited capacity for dispersal, their common ancestor likely diverged from other Attagenini before the breakup of Pangaea. Whatever the pathways of the ancestral form prior to and following the breakup, other insect species seemingly followed it. Among the Attagenini are two morphologically nearly identical arenicollis species (both needing generic reassignment): Novelsis sabulorum Beal from sand dunes of California and Nevada and Sefrania bleusei Pic from sandy deserts of North Africa.

Figures

Figs. 1–5. Male of Egidyella arcana. 1) Outline of dorsum, drawn not showing setae; 2) lateral; 4) antenna; 5) phallus habitus, denuded; hind leg elevated to show abdominal sterna; 3) hind coxa, trochanter, and femur, ventral view. Each line 5 1 mm.