Litostilbus testaceus ( Fabricius, 1792 )

Gimmel, Matthew L., 2023, Distribution and Synonymy in New World Litostilbus Guillebeau (Coleoptera: Cucujoidea: Phalacridae), The Coleopterists Bulletin 77 (2), pp. 189-193 : 190-192

Litostilbus testaceus ( Fabricius, 1792) ( Figs. 1–17 )

Sphaeridium testaceum Fabricius 1792: 83 ; Phalacrus testaceus : Panzer 1805: 27; Litochrus testaceus : Erichson 1845: 109; Litostilbus testaceus : Guillebeau 1894: 310. Type locality: Saint Thomas, Danish West Indies (now US Virgin Islands, USA).

Ochrolitus tristriatus Casey 1890: 142 ; Litostilbus tristriatus : Gimmel 2013: 47; Ochrolitus triseriatus [lapsus calami]: Peck 2016: 134. Type locality: Key West, Florida, USA. New synonym.

Type Specimens. Sphaeridium testaceum : lectotype (originally ZMUC; now ZMUK) (see Gimmel 2013). Ochrolitus tristriatus : holotype, with the following labels: “Key West / Fla \\ CASEY / bequest / 1925 \\ TYPE USNM / 49012 [red label, number handwritten] \\ Ochrolitus / tristriatus / Csy. [handwritten]” ( USNM) .

Diagnosis. This species is distinguished from its Southeast Asian congeners by possessing one to three engraved striae (including sutural) on the elytron (one sutural stria in other species), the elytra uniformly testaceous, piceous, or bicolored testaceous-piceous (piceous with reddish macula or vittae in other species), and by the triangular shape of the fused parameres of the tegmen (duck-bill- or nipple-shaped in other known species).

Distribution. This species has been previously recorded under various names from Florida (USA), the Bahamas, the Cayman Islands, the US Virgin Islands, the British Virgin Islands, Antigua, Montserrat, Guadeloupe, Martinique, Saint Lucia, Saint Vincent and the Grenadines, Barbados, and Grenada ( Gimmel 2013; Ivie et al. 2008; Peck 2016; Thomas et al. 2013; Turnbow and Thomas 2008; Valentine and Ivie 2005). I have examined specimens from the following countries, islands, and provinces (repositories in brackets): Anguilla [USNM]; Antigua and Barbuda: Antigua [CMNC]; Bahamas: Andros [FSCA, MCZ], Frazer’s Hog Cay [AMNH], South Bimini Island [AMNH], Eleuthera Island [FSCA], Grand Bahama Island [USNM], Great Inagua Island [FSCA], New Providence Island [AMNH], Rum Cay [AMNH]; Barbados [CMNC]; Belize: Orange Walk District [FSCA, LSAM]; Brazil: Amazonas [BMNH]; British Virgin Islands: Anegada [WIBF], Eustatia Island [WIBF], Guana Island [UDCC, USNM, WIBF], Tortola [WIBF], Virgin Gorda [USNM, WIBF]; CaYman Islands: Cayman Brac [FSCA], Grand Cayman [FSCA], Little Cayman [FSCA]; Costa Rica: Guanacaste [INBio]; Cuba: Artemisa [USNM], Ciego de Ávila [MCZ], Cienfuegos [MCZ], Guantánamo [MCZ], Sancti Spíritus [FMNH], Santiago de Cuba [MCZ, WIBF]; Dominica [FSCA, USNM, WIBF]; Dominican Republic: Barahona [FSCA, WIBF], Duarte [MCZ], Independencia [WIBF], La Altagracia [WIBF], La Vega [FSCA, MLGC, UGCA, USNM, WIBF], Monseñor Nouel [FSCA], Monte Cristi [FSCA], Pedernales [FSCA, WIBF], Peravia [FSCA], San Pedro [FSCA]; Grenada [CMNC]; Guadeloupe [AMNH, CMNC]; Guyana [BMNH]; Haiti: Artibonite [FSCA], Grand’Anse [MCZ], Ouest [BMNH]; Martinique [CMNC]; Montserrat [WIBF]; Panama: Panamá [FSCA, UGCA]; Peru: Tambopata [SEMC]; Puerto Rico: Mona Island [WIBF], Puerto Rico Island [AMNH, FSCA, LSAM, MCZ, WIBF]; Saba [WIBF]; Saint Kitts and Nevis: Nevis [WIBF], Saint Kitts [FSCA, WIBF]; Saint Lucia [CMNC]; Saint Vincent and the Grenadines: Bequia [CMNC], Mayreau [CMNC], Saint Vincent [CMNC], Union [CMNC]; US Virgin Islands: Buck Island [WIBF], Saint Croix [OSUC, USNM, WIBF], Saint John [OSUC, WIBF], Saint Thomas [WIBF, ZMUC]; USA: Florida: Broward Co. [FSCA], Collier Co. [FSCA], Dade Co. [AMNH, FSCA, OSUC], Monroe Co. [TAMU, UGCA, USNM], Palm Beach Co. [AMNH, CMNH], Pinellas Co. [FSCA].

Variation. Specimens range from almost uniformly piceous to uniformly testaceous dorsally ( Figs. 1 , 7, 9 ) but most frequently are brownish with the elytra diffusely to distinctly paler in the apical third to half ( Figs. 6, 8 ). Some specimens are paler near the base of the elytra ( Fig. 8 ). The number of engraved striae on each elytron varies from one to three. Floridian , Bahamian , and West Indian specimens normally exhibit three such striae ( Fig. 1 ), with a few inland Hispaniolan specimens exhibiting only two. Occasional specimens have stria 2 “skipped” such that only striae 1 and 3 are fully expressed ( Fig. 8 ). Among specimens (n = 4) from one locality in Barahona Province, Dominican Republic ( FSCA), three forms were observed: one with three engraved striae, one with two engraved striae, and two with striae 1 and 3 (second stria “skipped”). Most Panamanian and South American specimens showed two sutural striae on the elytron ( Fig. 9 ), while most Costa Rican and Belizean specimens presented one stria. There are also subtle differences in the relative proportions of the antennomeres of the club, extent of the protibial ctenidium, and level of setation on the prosternal process .

Some variation in shape of the tegmen and median lobe of the aedeagus is evident among dissected specimens of New World Litostilbus ( Figs. 10–17 ). While more notable than in other purported species of Phalacridae , this variation is modest when compared to the interspecific variation evident in Old World species of Litostilbus ; compare, e.g., the aedeagal illustrations for Litostilbus festivus (Motschulsky, 1858) and Litostilbus borneensis ( Lyubarsky, 1994) in Liubarsky (1993: fig. 19) and Lyubarsky (1994: fig. 8), respectively. The variation within L. testaceus primarily pertains to the shape and proportions of the triangular fused parameres of the tegmen ( Figs. 10, 12, 14, 16 ) and the bilobed apex of the median lobe ( Figs. 11, 13, 15, 17 ). Apparent variation in the ventral aspect of the fused parameres in the figures is primarily due to the foreshortening of the structure based on varying position, as evidenced in the respective lateral views. This subtle aedeagal variation along a spectrum of states, in combination with the widespread variation in coloration and strial configuration among single collecting events in the specimens noted above, leads me to conclude that these form a single, variable species of Litostilbus in the New World. As a consequence, Casey’s L. tristriatus becomes a junior subjective synonym, and the name L. testaceus takes precedence.

Remarks and Biology. The habits of this species are poorly known; collection labels indicate that it is frequently collected at blacklight, while a long series from the Bahamas (Andros; FSCA) was collected from a trunk of Coccoloba diversifolia Jacq. ( Polygonaceae ) at night.A series of three specimens from Peru (Puerto Maldonado; SEMC) was collect- ed from smooth Hypoxylon Bull. ( Hypoxylaceae ) fungi; a dissected specimen from Belize (FSCA) had unidentified dark fungal spores in the hindgut. Specimens in the West Indies have been taken by beating dead branches with dry leaves attached (M. A. Ivie, in litt.).

Figures

Figs. 1–5. Litostilbus testaceus, specimen from Pinellas Co., Florida, USA (FSCA).1) Dorsal habitus; 2) Lateral habitus; 3) Ventral habitus; 4) Closeup of protibia, arrow indicates protibial ctenidium; 5) Frontal. Images by Lucie Gimmel.

Figs. 6–9. Litostilbus testaceus, dorsal habitus showing variation. 6) Specimen from Dade Co., Florida, USA (FSCA); 7) Specimen from Andros Island, Bahamas (FSCA); 8) Specimen from Virgin Gorda, British Virgin Islands (USNM); 9) Specimen from Tambopata Province, Peru (FSCA). Images by Lucie Gimmel.

Figs. 10–17. Litostilbus testaceus, male genitalia showing variation. Specimen from Monroe Co., Florida, USA (USNM): 10) Tegmen, lateral and ventral; 11) Median lobe, ventral. Specimen from Guana, British Virgin Islands (USNM): 12) Tegmen, lateral and ventral; 13) Median lobe, ventral. Specimen from Belize (FSCA): 14) Tegmen, lateral and ventral; 15) Median lobe, ventral. Specimen from Guyana (BMNH): 16) Tegmen, lateral and ventral; 17) Median lobe, ventral.