Xystosomus elaphrinus Bates, 1863

Erwin, Terry L., 1973, Studies of the subtribe Tachyina (Coleoptera: Carabidae: Bembidiini), Part I: A revision of the Neotropical genus Xystosomus Schaum, Smithsonian Contributions to Zoology 140, pp. 1-39 : 21-22

17. Xystosomus elaphrinus Bates

FIGURES 1 , 37 , 40 , 42 , 70

Xystosomus elephrinus Bates, 1871b:267 . [Lectotype, male, in MHNP, here selected. Type-locality: Ega (Teffe) , Brazil.]

DESCRIPTION.—Form: Similar to members of the holarctic genus Elaphrus , with broad elytra, narrow pronotum, and huge eyes.

Color: Head and body piceous; pronotum and elytra with metallic green luster; appendages testaceous or piceous or bicolored.

Head: Broad between eyes; frontal furrows well impressed and separated from eye by a linear costa; eyes huge and hemispherical.

Pronotum ( Figures 1 , 37): Quadrate (W/ L, x 1.45; range, 1.35-1.53; 29 specimens); lateral setigerous pores present just anterior to middle and at hind angles; laterobasal carina well developed; hind angles sharp, acute, sides anterior to angles sinuate; side margins broadly explanate to lateral setigerous pores, narrowly explanate anterior to pores.

Elytra: Each elytron with eight rows of serial

punctures, the lateral three or four rows also striate in part; punctulae and punctures larger and more coarsely impressed in rows 3-8 at base; all rows finer or effaced at apex; lateral intervals convex,

discal intervals flat, intervals between coarse basal punctures uneven and partially convex; side margins broadly explanate; humeral projection well developed, obtuse; chaetotaxy as in X. gruti ; plica short, evident externally.

Microsculpture: As in X. gruti , except more finely impressed or nearly effaced in part; head shiny and without meshes.

Secondary sexual characters: Male genitalia characteristic of gruti group members in internal sac; median lobe larger, more twisted, and with bent apex ( Figure 40 ). Female genitalia as in X. gruti , except stylus ( Figure 42 ) blunt at apex, exceeded in length by lateral spines.

Size: Twenty-nine specimens: length, 3.7-4.3 mm; width, 1.6-1.9 mm.

VARIATION.—The specimens I have seen can be divided into two groups on the basis of elytral punctation and leg color. One morph (all specimens south of the Amazon Basin or in the southern part of it) has each elytron with eight entire rows of numerous small serial punctulae with small, noncoarse punctures basally in rows 4—6. This morph has testaceous legs. The other morph (all specimens from French Guiana north) has each elytron with eight abbreviated rows of either small punctulae (rows 1 and 2) or large, coarse, well-impressed punctures (rows 3-8) with only rows 7 and 8 entire; rows 1-6 effaced in apical half. This morph has piceous or darkly infuscated legs.

Unfortunately, all "pale-legged morph" specimens are females. Further material, especially males, may clarify the situation and indicate

whether the southern form is conspecific (or perhaps subspecific). The type-specimen is from an intermediate area, but it agrees in all respects to the northern "dark-legged morph."

NATURAL HISTORY.— Adults were collected January to March, in May, July to September, and in November. One teneral specimen was collected in July. Nevermann recorded four specimens from "under loose bark, January, July, September, November"; one specimen "on tree fungus, February"; one specimen "off pieces of bark, May"; and one specimen "at light, May."

DISTRIBUTION ( Figure 70 ).—The range of this species extends from Costa Rica to the Amazon Basin in lowland tropical forests.

LOCALITY RECORDS ( Figure 70 ).—I have seen 30 specimens from the following localities:

CENTRAL AMERICA: COSTA RICA: Hamburg Farm at Reventazon (USNM); Lasmercedes (USNM). PANAMA: Bugaba (MHNP); Cabima (USNM); Matachin (MHNP). SOUTH AMERICA: BRAZIL: Amazonas Province: Teffe (MHNP). Goyaz Province: Jatahy (MHNP), Rio Verde (MHNP). Pari Province: Baragance (MHNP). BRITISH GUIANA: Bartica (MHNP); Kartabo Point (MCZ). COLOM-

BIA: San Carlos (MHNP). FRENCH GUIANA: Cayenne (MHNP); Roches de Kourou (MHNP).

Figures

FIGURE 1.—Habitus of Xystosomus elaphrinus, male, from Kartabo Point, British Guiana.

FIGURE 42.—Female genitalia, ventral aspect, left side, of Xystosomus elaphrinus, Lasmercedes, Costa Rica.

FIGURE 70 Approximate ranges of the elaphrinus group (crosshatched area) and the micro- tretus group (solid areas).

FIGURES 37-39.—Pronotum, dorsal aspect: 37, Xystosomus elaphrinus, male, Roches de Konrou, French Guiana; 38, X. notiophiloides, female, Jatahy, Brazil; 39, X. spangleri, female, 9.0 miles west of Los Algarrobos, Panama.

FIGURES 40, 41.—Male genitalia, left lateral aspect: 40, Xystosomus elaphrinus, Kartabo Point, British Guiana; 41, X. spangleri, 9.0 miles west of Los Algarrobos, Panama.