Hister criticus

Caterino, Michael S., 2004, Taxonomy of the Hister criticus group, with description of a new species (Coleoptera: Histeridae), Zootaxa 601, pp. 1-16 : 3-4

Diagnosing the Hister criticus group

There is no single character by which this group may consistently be distinguished from all other New World Hister . They are not keyed out as a group in either of the previous two papers with keys to New World Histerini ( Caterino, 1999a, 1999b; in the latter keying out in the second halves of couplets 8 and 11). But through a combination of nearly constant characters, rare or absent in other groups, it is possible to separate these species from other New World Hister . These characters include (listed from most to least distinctive):

Pronotum unistriate, with the single lateral stria continuous with the anterior marginal stria behind the anterior pronotal emargination ( Figs. 3 , 7 ). While a few other New World Hister have just a single lateral stria (most have two), it usually ends freely in front (e.g. in H. sallei Marseul , and H. matador Caterino ). Hister litus Marseul , H. californicus Marseul and H. gringo Caterino share this configuration of pronotal striae with the criticus group. However, these are easily separated by the absent, or at least strongly reduced sutural elytral stria. In case of doubt the aedeagus of members of the litus group, with its elongate basal piece, is highly distinctive (see Caterino, 1999a for details and illustrations).

Protibia tridentate, with apical tooth bispinose and submarginal carina complete. This character is essentially invariant in the group ( Fig. 5 ), while varying widely in other New World Hister . It is only difficult to apply to worn specimens (a surprisingly common condition in H. foveipygus Wenzel & Dybas and H. guanacaste n. sp.). A fourth protibial tooth is seen in rare individuals, but usually only on one leg. The only other conceivably sympatric Hister to share this protibial configuration would be H. depurator Say (in the US southwest), which always has two lateral pronotal striae. Many members of the Hister servus group have the tibiae similarly dentate. But in these the submarginal carina is only present basally, meeting the lateral margin at one of the basal marginal teeth.

Propygidium and pygidium, as well as apical margin of each elytron, with conspicuous transverse microsculpture. This microsculpture may be largely obscured by coarse punctures on the propygidium and pygidium, but is even in these cases visible around the edges of the punctate areas. This distinctive microsculpture is also seen in a few other sympatric Hister spp.

Subhumeral elytral striae absent. The absence of these striae, while invariant in this group, is also observed in several other neotropical Hister in various groups.

Postmetacoxal stria doubled along inner margin of metacoxa. This character is apparently unique among neotropical Hister , though it is somewhat variable in H. foveipygus , with some individuals having only a single postcoxal stria, or only vague fragments of a second.

Supraorbital stria absent. While this is actually true of most other New World Hister , it is a useful feature by which to separate the group from the otherwise rather similar species H. servus Erichson and H. nodatus Lewis , both of which have the frontal stria continuous with a complete supraorbital.

Median lobe of aedeagus with one pair unarticulated apical armature, and with median acute process ( Fig. 6 D). The form of the aedeagus is strongly conserved in this group, with only minor variation in tegmenal shape evident. Superficially this type of aedeagus appears very similar to that seen in many members of the H. servus group. However, as far as I have been able to tell, the similar­looking apical armature of the median lobe in the criticus group is unarticulated, while in the H. servus group each arm of this structure rotates outward into tegmenal grooves upon extrusion of the median lobe.

Figures

FIGURE 3. Dorsal habitus photographs of Hister spp. A. Hister criticus; B. H. laevimargo; C. H. latimargo.

FIGURE 5. Posterior view of protibiae of Hister spp. A. Hister criticus; B. H. latimargo; C. H. guanacaste; D. H. foveipygus.

FIGURE 6. Dorsal view of components of aedeagus of Hister spp. A. Tegmen of Hister criticus; B. Tegmen of H. guanacaste; C. Tegmen of H. foveipygus; D. Median lobe of H. foveipygus.

FIGURE 7. Dorsal habitus photographs of Hister spp. A. Hister guanacaste; B. H. foveipygus.