Arenivaga (Rehn, 1903)

Hopkins, Heidi, 2014, A revision of the genus Arenivaga (Rehn) (Blattodea, Corydiidae), with descriptions of new species and key to the males of the genus, ZooKeys 384, pp. 1-256 : 13-16

Genus Arenivaga (Rehn, 1903) Figures 33-34

Homoeogamia (Arenivaga) Rehn 1903, Proceedings of the Academy of Natural Sciences of Philadelphia, Vol. 55, p. 188.

Arenivaga , Caudell 1913, Proceedings of the United States National Museum, Vol. 44, p. 605.

Type species.

Arenivaga bolliana (Saussure) by original designation.

Distribution.

The genus Arenivaga is found in central Florida and from Texas to California south into Mexico. They occur from about 39°N south to about 18°N (See Fig. 10).

Diagnosis.

Until now, Arenivaga were diagnosed from other Corydiid genera by the presence of cercal tricholiths (Fig. 7) and genicular spines on the meta- and mesothoracic legs (Fig. 5). The sister genus Eremoblatta , has cercal tricholiths but no genicular spines on the legs. A new species described in this work ( Arenivaga diaphana ) has polymorphic genicular spines, the majority of specimens studied having no genicular spines but two specimens were found with the characteristic Arenivaga genicular spine distribution. This undermines the character that until now separated Arenivaga from Eremoblatta . A gestalt of the phenotype of both sexes of the two genera allow easy determination between the two. But without some familiarity with both genera, or examples of both genera side by side, this method of determination is difficult. Generally speaking, Eremoblatta are smaller than Arenivaga and have pronota of consistent size with no pattern; the wings of the males are consistently glossy and wrinkled, and the females are considerably more hirsute than Arenivaga females. Eremoblatta do not appear to show intraspecific phenotypic variability due to variation in environment as do many Arenivaga species. The vast majority of Arenivaga specimens possess genicular spines on the meta- and mesothoracic legs, and the majority of specimens that lack genicular spines will be Eremoblatta . Genitalia provide a clear distinction as Arenivaga has a single-pronged genital hook and Eremoblatta 's is double-pronged.

Description.

Male. Measurements. Holotype TL = 24.6 mm, GW = 13.0 mm, PW = 8.64 mm, PL = 5.60 mm, TL/GW = 1.89, PL/PW = 0.65. EW = 0.40 mm; OW = 0.60 mm. Among paratypes range of TL 20.1-30.7 mm; range of GW 9.6-15.3 mm; range of PW 7.25-10.10 mm; range of PL 4.74-6.17 mm.

Head. Two ocelli large, ovoid and protruding; vertex flat, variable in color and width, most species with small ridges between apices of eyes that extend onto ocellar tubercles; interocellar space concave, of varying width, concavity depth and color. Frons color variable, tectiform, concave and/or with fine horizontal corrugations; margined on each side by ridges extending from medial margins of ocelli laterally to margins of clypeus with long or very long setae. Anterior portion of frons of variable color, bulbous to very bulbous in most species; clypeal suture with two proximal setae demarcating anteclypeus; labrum wide. Eyes large and reniform, medially emarginate, dark brown in life but color various in dried specimens. Antennae long, delicate and filiform, arising from medial emargination of eyes; antennomere number variable from ~53-67, though determination is made difficult by frequency of broken antennae on specimens.

Pronotum. Pronotum elliptical, variable in size, anterior margin convex, extending anteriorly over head; broad anterior margin translucent, waxy light brown. Setae of variable length along anterior margin; pale short dense setae projecting from ventral side of posterior margin; dorsal surface of pronotum covered with short setae; pronotal pattern may be impressed into surface or not, well demarcated or not, widely variable in color even within some species, with varying extent of aura; the pattern itself varies across the group and takes on certain distinctive appearances including semblance of “panther” or “hippo” faces, and, more rarely, a “koala” face pattern (Fig. 8).

Body. Abdomen and legs dorso-ventrally flattened; all legs heavily spinous and setose. Legs and body varying in color, often within a species; white deposits of uric acid visible through exoskeleton throughout body, legs, pronotum, and wing venation. Sternites rounded and setose laterally in most species. Wing brace (Fig. 5) may be present or absent but is consistent within each species. Tarsi with tarsomere I length equal to length of II-V combined; tarsomere IV shortest; with genicular spines on meso and metalegs (but see Diagnosis, above). Two tarsal claws present in all species but one. Subgenital plate asymmetrical with posterior edge emarginated, apices variable in shape; setose along posterior edge and posterior half of dorsal and ventral surfaces.

Forewings. Wings extended beyond abdominal apex to varying degrees; veins distinctly raised above surface anteriorly and laterally, becoming increasingly embedded in surface posteriorly and centrally; color ranges from pale clear golden tan to very dark brown; blotchiness absent in some species, consistent in others, variable in others; surface ranges from opaque to semi-opaque to translucent, and from matte to shiny; with variable length setae on anterior lateral edges decreasing to uniformly small posteriorly.

Genitalia. Distinctive and highly sculptural, the genitalia of Arenivaga distinguish and delimit species. This revision names and describes four phallomeres, though alternate interpretations of the limits of these structures are possible. While the structures are easy to homologize between species of the genus and close relatives, they are extremely difficult to homologize with the genitalia of other cockroach families or with a “generic” cockroach and no such analysis is attempted here. The phallomeres used in this revision are the right dorsal phallomere, the right ventral phallomere, the small central sclerite, and the left phallomere which includes the genital hook (Fig. 7). The two right phallomeres are hinged together on the lateral side of the animal but are disarticulated here prior to drawing so that as much detail as possible may be shown (Fig. 7).

Habitat and natural history.

Arenivaga , Latin for "sand runner", are found in the American southwest, Mexico, and Florida (Fig. 10). Females and nymphs are subterranean in sandy, dune habitats, feeding on mycorrhizal fungi, leaf detritus of desert shrubs, and the seeds collected by the mammals whose burrows they cohabit ( Cohen and Cohen 1976, Hawke and Farley 1973). Their cryptic life history has never been fully documented although their adaptations for life in the desert are well-studied ( Walthall and Hartman 1981, Edney 1968, Hawke and Farley 1971a, 1971b, 1973, Cohen and Cohen 1976, 1981, Edney and McFarlane 1974, Hartman et al. 1987, Edney et al. 1974, 1978, Jackson 1983, O’Donnell 1977, 1981, 1982, Appel et al. 1983). Mature males, the only winged form, live most of their short lives above-ground ( Appel et al. 1983). Females are most active near and at the surface during summer, which is most likely the mating season. Mature females “swim” to the surface after dark when the first few centimeters of sand have cooled. There, they wander the surface of the sand, presumably attracting males using pheromones ( Hawke and Farley 1973). Courtship has never been observed, but mating proceeds in the typical end-to-end manner found in other Blattodea (Figure 11).