MICRATOPUS CASEY IN THE UNITED STATES ( COLEOPTERA : CARABIDAE : BEMBIDIINAE ) By

The late Rene Jeannel (e.g., 1946, p. 331) divided the bembidiine carabids, which he regarded as a subfamily Bembidiitae, into four tribes: Anillini, Limnastini, Tachyini, and Bembidiini. He included Micratopus Casey (1914, p. 42) and Limnastis Motschulsky in the Limnastini, although the former genus had previously formed the type of Casey’s tribe Micratopini. Ball (i960) retained Micratopini as a tribe of the Carabidae, but his “Bembidiini” is equivalent to the “Anillini”, “Tachyini”, and “Bembidiini” of Jeannel. Ball’s classificatory scheme thus implies that Limnastis and Micratopus are phylogenetically so remote that they merit a hierarchical status equivalent to that of all other bembidiines. Prior to his death Dr. Jeannel {in litt . ) indicated to me that he had used the name Limnastini rather than Casey’s older name Micratopini because he had not examined sufficient material of Micratopus and preferred the name of the tribe to be based on a well-known genus. After comparison of several species of Micratopus with several Old World species of Limnastis sent to me by Jeannel

Prior to his death Dr. Jeannel {in litt . ) indicated to me that he had used the name Limnastini rather than Casey's older name Micratopini because he had not examined sufficient material of Micratopus and preferred the name of the tribe to be based on a well-known genus. After comparison of several species of Micratopus with several Old World species of Limnastis sent to me by Jeannel I see no reason not to apply the law of priority and accept Casey's tribal name Micratopini, with Limnastini a synonym. However, Micratopini would become at best a subtribe in Bembidiini s. lat.
in the classification of Ball (i960).
Parenthetically it should be noted that Horologion speokoites Valentine (1932), an eyeless carabid known only from the unique holotype male taken in a West Virginia cave, has many features in common with the more primitive bembidiines (cf. Barr, 1969, p. 87). In my opinion it should be included within the subfamily Bembidiinae (or tribe Bembidiini s. lat.) close to and perhaps hierarchically coequal with the Anillini, rather than be relegated to the Psydrini, as was suggested by Valentine (1932) and actually done by Ball (i960). Casey, 1914, p.  Length 2. 1-2.5 mm-Dorsum of head dark chestnut; clypeus, labrum, antennae, pronotum and elytra brownish-piceous ; maxillary and labial palps, femora, coxae, and underparts of tibiae and tarsi flavotestaceous. Microsculpture of pronotum and elytra a very fine, anastomosing meshwork which imparts an opalescent cast; microsculpture of head isodiametric, open; integument more or less pubescent, least so on dorsum of head.

Micratopus Casey
Head with sides convergent, a little longer than wide, dorsum with minute punctures sparsely scattered and visible only at high magnification; labrum deeply emarginate, lateral lobes folded down over and partly obscuring mandibles, anterior margin bearing only four setae; mandibles short, thick, bifid at tip, without a seta in scrobe; mentum edentate, submentum with four (prebasilar) setae; maxillary and labial palps about as in Limnastis , penultimate segments inflated, heavily pubescent, last segments minute, hyaline, glabrous; clypeus with a seta at each side, clypeolabral suture arcuate, convex forward ; frontal grooves shallow and very short, convergent eyes large and freely convex; only one pair of supraorbital setae.
Pronotum about seven-tenths as long as wide, sides rounded and very feebly sinuate before the rounded, obtuse hind angles; base oblique behind hind angles, so that base is feebly "lobed" ; marginal gutter rather broad, hind angles not carinate ; disc sparsely pubescent. Elytra broad, depressed, subparallel, humeri prominent and apexes broadly truncate, length almost 1.5 times combined width; longitudinal striae moderately deep, distinct, interstriae each with a row of short pubescence; a single discal puncture on third stria near apex; umbilicate series with whips in punctures 1, 6, and 8.
Antenna about six-tenths as long as body, segments II and III subequal and about six-tenths as long as segment IV; all segments more or less pubescent, but becoming more so from scape to segment Aedeagus ( Figure 2) highly modified, trapezoidal, short, thick, and laterally compressed, about 0.16 X 0.30 mm. long; right side with a loosely attached lamina projecting a short distance upward and forward and articulating with a single slender (left?) paramere bearing two seatae at its apex; basal orifice a simple slot with no evident lobes; aedeagus walls thin, hyaline, with a thin sclerotized strip antero-dorsally and another, vertical strip at apex on left side ; internal sac with six rather complex sclerites : 1 ) basoventral scroll-shaped, bifurcated, with minute spines internally; (2) dorsal: a slender, horizontally oriented, arcuate spicule; 3) basal: a slender, vertically oriented, arcuate spicule; 4) first medial: broad, bilobed, with a dorsal hook and ventral projection; 5) second medial: slender, bilobed, dorsal lobe bifurcate; and 6) apical: a blade-like hook.
Measurements of a male from Gaits Landing, Cherokee County, Georgia (T. Barr, private collection) : total length 2.44 mm., head 0.48 mm. long X 0.44 mm. wide, pronotum 0.50 mm. long X 0.68 mm. wide, elytra 1.46 mm. long X 1.01 mm. wide (com- The range of M. aenescens is thus outlined as predominantly the Gulf Coastal Plain, with significant penetration northward into the Interior Low Plateaus (to Hardinsburg, Indiana). Leng (1920, p. 54) lists the species from "N.C.", and it must certainly occur in Kentucky and possibly in southeastern Virginia. The apparent absence of Micratopus from southeastern Texas is probably a collecting accident.
Discussion : -The species of Micratopus are differentiated with some difficulty, primarily because the range of variation within a species is difficult to determine with scattered material. Most of them, like M. aenescens , are probably rather widely distributed. The aedeagi resemble that of aenescens but are not easy to extract from dried specimens and are usually difficult or impossible to interpret unless several preparations are made. The accompanying figure of the aedeagus of M. aenescens (Fig. 2) was made with camera lucida but represents a composite of four aedeagi extracted from specimens at the same locality. I believe that the six minute sclerites of the internal sac, described in some detail for aenescens , have homologues in the Mexican and Central American species as well as those of the West Indies, and may prove to be of value in a diagnostic sense when the genus as a whole is investigated.
The complex aedeagal structure presumably represents an aberrant and peculiar specialization. As such, it is of little help in determining the position of Micratopus within a bembidiine classificatory scheme.
The external resemblances to Limnastis, however, leave little doubt that the two genera are closely related. Common features include