Within the Clivinini. the subtribe Ardistomina is characterized as follows: Elytron latero-distally (Fig. 22) with a plica (ep) and an adjacent abdominal (segment VII) pleural projection (app) that together form an elytral-abdominal locking mechanism; ovipositor (Figs 27–30) with an asetose quadranguloid laterotergite, and unsegmented gonocoxa bearing at apex few long setae.

This subtribe includes Aspidoglossa Putzeys, Semiardistomis Kult, and Ardistomis Putzeys.

Mandibles, labium, and female genitalia (source of many diagnostic features within the tribe Clivinini) were compared within the ardistomines and between that subtribe and selected members of the nominotypic Clivinina. The latter taxon was represented by Western Hemisphere members of six exemplar genera: Clivina Latreille, Oxydrepanus Putzeys, Schizogenius Putzeys, Ancus Putzeys, Nyctosyles Putzeys, and Obadius Burmeister. Also, mandibles of Dyschiriodes Jeannel (subtribe Dyschiriina) were included.

Mandibles: Compared to those of Dyschiriina (Figs 12A–12D), the mandibles of the clivinines (Figs 9A–9D to 11A–11D) and ardistomines (Figs 6A–6D to 8A–8D) are relatively straight.

For dentition, Dyschiriodes exhibits the least number of occlusal teeth. The clivinine genera Clivina (Figs 9A–9D)and Oxydrepanus (Figs 10A–10D), and the ardistomine genera Aspidoglossa (Figs 8A–8D) and Ardistomis (Figs 7A–7D)have a full complement of occlusal teeth, Semiardistomis (Figs 6A–6D) and Schizogenius (Figs 11A–11D) lack the premolar tooth.

In values for L/W (a measure of relative length), the mandibles of clivinines, dyschiriines, and the ardistomine Aspidoglossa are relatively short (L/W 1.44–1.68), whereas the mandibles of the ardistomine genera Semiardistomis (L/W 1.86) and Ardistomis (L/W 2.25) are relatively long, with a slender terebra.

Labium: In form, the mentum (m) is markedly to slightly transverse (L/W 0.43–0.56) among the clivinine genera (Figs 17A–21A); among the ardistomine genera (Figs 13A–16A) the mentum is slightly transverse to slightly elongate (L/W 0.57–0.95), a morphocline being Aspidoglossa—Semiardistomis—Ardistomis.

In the Ardistomina, the apex of the lateral lobes (ll) is extended distally beyond the apex of the mental tooth (mt). This feature is varied among the clivinines: lateral lobes not extended beyond the apex of the mental tooth (Clivina, Oxydrepanus, and Nyctosyles, Figs 17A, 18A, 21A), to slightly extended beyond that line (Schizogenius and Ancus, Figs 19A, 20A).

The paraglossae (pg) are elongate, extended distinctly beyond the apex of the glossal sclerite (gs) in most genera of Ardistomina and Clivinina. In the ardistomine Ardistomis (Fig. 15B) and clivinine Nyctosyles (Fig. 21B) the paraglossae are much shorter than the glossal sclerite.

The glossal sclerite (gs) varies appreciably in both subtribes, being very large and rotund in Semiardistomis (Figs 13B, 14B4), broad with a broad apex in Nyctosyles (Fig. 21), and narrower and shorter in the remaining ardistomines and clivinines.

The glossal sclerite in the genus Semiardistomis has an extra pair of preapical setae (Figs 13B, 14B, pas). All other ardistomine and clivinine genera have a single pair of glossal setae (as).

Labial palpomere 3 (lp3) is elongate and fusiform in the Ardistomina (Figs 13A–16A). This sclerite varies in the clivinines: fusiform in Clivina (Fig. 17A), and variously widened in the remaining clivinine exemplar genera (Figs 18A–21A).

Female genitalia: The ovipositor sclerites come in two types, either ardistomine (Figs 27–30) or clivinine (Figs 31A–36A). For clivinine genera Clivina, Nyctosyles and Obadius, the gonocoxa is segmented, each segment designated as a gonocoxite (gc1, gc2). Gonocoxite 2 is more or less falcate. In ardistomine females, in contrast, the gonocoxa (gc) is unsegmented, and slightly curved or essentially straight. The laterotergites (lt) of clivinines are more or less triangular, whereas those of ardistomines are rectanguloid. Further, the laterotergites and gonocoxites of clivinines are setose along their margins, but the apex of gonocoxite 2 is glabrous. In contrast, for ardistomines, the ovipositor sclerites are essentially glabrous, but the apex of the gonocoxa bears a few setae. An unsegmented gonocoxa with reduced number of setae is also seen in Dyschiriina (Fedorenko, 1996). Within the ardistomines, the gonocoxae of Aspidoglossa and Ardistomis are moderately broad (Figs 29, 30), but those of Semiardistomis (Figs 27, 28) are slender, virtually rod-like.

Within the Clivinina, the reproductive tract (Figs 31A–36A) is strikingly varied, but the range of variation is about as extensive as, and similar to, that of the Ardistomina, and thus uninformative from a diagnostic perspective at subtribal level. Within each subtribe, the genera are clearly distinguishable from one another. Here, I treat only the ardistomine genera.

In Aspidoglossa females (Fig. 30), the spermathecal duct (spd) is narrow, elongate, with few loose coils proximally; the spermathecal gland (spgd) is relatively short. The female tract of Ardistomis (Fig. 29) is narrow, relatively short; the spermatheca (sp) is moderately long and markedly expanded distally. For Semiardistomis females (Figs 27, 28) the reproductive tracts of the two species-groups are sufficiently different from one another to require separate descriptions. They also differ markedly from the reproductive tracts of Aspidoglossa and Ardistomis. For details, see species-group treatments, below.

The members of the Ardistomina are hygrophilous or mesophilous, living in riparian situations, lowland swamp forests, or wet montane tropical forest.

As indicated above, of the three ardistomine genera, Aspidoglossa is most similar to members of subtribe Clivinina in mandibular and mental proportions and is more remote from Ardistomis and Semiardistomis in structure of the female reproductive tract than the latter two genera are from each other. In turn, Ardistomis and Semiardistomis share elongate mandibles and mentum. Based on these observations, I conclude that relationships of these three genera may be summarized using brackets as follows: [Aspidoglossa [Ardistomis + Semiardistomis]]

This subtribe is a Western Hemisphere indigenous group. Its range extends in South America east of the Andes mountain range from central Argentina northward through Colombia, Middle America, and the West Indies to temperate North America, principally east of the Mississippi drainage basin.