Tachyta (Tachyta) angulata Casey 1918

Tachyta angulata Casey

Tachyta angulata Casey, 1918:216 [lectotype, male, USNM, designated by Erwin, 1974b:150; type-locality: Bayfield, Wisconsin].

DIAGNOSIS.—The flat frontal area, abruptly sinuate sides of the pronotum, and elongate elytra make these beetles the most distinctive of the genus.

DESCRIPTION.—Form (Figure 97): Very elongate and narrow, strongly depressed; head broad and flat with small but prominent eyes.

Color: Dull piceous or almost black in some fully matured specimens; appendages flavous except distal antennal articles, which are infuscated.

Head (Figure 113): Very broad and flat, slightly narrower across eyes than pronotum across anterior angles; frontal furrows very shallow and poorly delimited medially, lateral carina low and not well developed, anterior supraorbital seta in shallow fovea; front between eyes with scattered punctulae, punctulae not arranged in transverse band; eyes small and prominent. Mouthparts (Figure 112).

Pronotum (Figure 114): Narrow and more cordiform than in T. falli members, with disc very dpressed medially and only slightly convex laterally; sides convergent posteriorly and abruptly sinuate just before hind angles, margins narrowly beaded, not reflexed, surface laterobasally with well-developed carina, carina short; hind angles slightly acute; basal transverse impression well impressed laterally, broadly interrupted medially and not confluent with median line; anterior angles prominent, not produced. Male anterior tarsi (Figure 116, 117).

Elytra (Figure 115): Suturai interneur entire, striate, and lightly impressed throughout, interneurs 2 to 5 striate and feebly impressed, ended about apical third, lateral interneurs effaced, interneur 8 sulcate anteriorly and posteriorly, almost or completely effaced at middle; humeral margin rounded to base of interneur 5, margin broadly reflexed and explanate from humerus to plica, edge finely setulose behind humerus; chaetotaxy as in T. nana members except Ed 3 position unstable (see below); plica well developed and visible externally.

Microsculpture (Figures 118–120): Well impressed, almost perfectly isodiametric microreticulation over entire dorsal surface, meshes mostly forming transverse rows.

Genitalia (Figure 100): Male internal sac complex, phallus with broadly rounded apex (7 examined); female as in T. falli members (10 examined).

Size: Length, 2.60 to 3.10 mm; width, 1.04 to 1.40 mm, 8 specimens measured.

VARIATION.—The color varies with the age of the specimen. The position of Ed 3 varies from anterior of Eo 4 to posterior of Eo 4, and Ed 3’s of each elytron vary with respect to each other. The elytral interneurs are more deeply impressed in the Mexican specimens.

NATURAL HISTORY.—Adults have been found from February to November; teneral adults were found in August. It is likely that hibernation takes place in the adult stage and that larvae can be found in early summer. Elevation records indicate an altitudinal range from near sea level in the north to about 3700 m in Mexico. Lindroth (1966) indicates that specimens were found under bark of Pseudotsuga menzieii. I have seen specimen labels which indicate that the attached specimens were found under bark of Betula lutea (New York), Populus sp. (British Columbia), and Acer sp. (Maryland). One specimen from Quebec was found in “Berlese sample ex lining of deserted beaver lodge,” and it is likely that the specimen came from under bark of one of the beaver’s trees.

DISTRIBUTION (Figure 121).—The range of this species is vast and extends from Nova Scotia west to Yukon and British Columbia and south to Veracruz, Mexico. The species is known from both the Sierra Madre Oriental and Sierra Madre Occidental in Mexico.

The nana group

Members of the nana group are characterized by their complex and highly similar endophalli and elytral chaetotaxy. Members of both species are strongly microsculptured dorsally. One species is polytypic and widely distributed; the second species is only in the southern and eastern United States.

Both species occur under bark of conifers; T. nana also occurs under bark of hardwoods.

The combined range of the two species in this group can be described as Holarctic.

Tachyta angulata is a species of ground beetle in the family Carabidae. It is found in North America.