Isthmiade Thomson, 1864

Clarke 1, Robin O. S., 2009, Bolivian Rhinotragini II: ISTHMIADE Thomson, 1864 (Coleoptera, Cerambycidae), with two new species Robin O. S. Clarke, Papéis Avulsos de Zoologia 49 (44), pp. 577-591 : 578-579

Isthmiade Thomson, 1864

Isthmiade Thomson, 1864: 166 , 1865: 417; Lacordaire, 1869: 504; Bates, 1870: 326, 1873: 121; Zajciw, 1972b: 575 (rev.).; Monné, 2006: 481 (cat.).

Type-species: Isthmiade hephestionoides Thomson, 1864 (original designation) [= Stenopterus braconides Perty, 1832 ].

The following description of the genus is translated from Zajciw (1972b), with author’s rewording in square brackets:

Body black, rufous or testaceous, with parts or fasciae black; slender, elongate, more or less narrow. Clypeus smooth or punctate, sometimes pubescent. Eyes very finely granulate. Antennae not passing beyond middle of urosternite III [must be changed to apex of urosternite III to include some males of I. laevicollis and female Isthmiade zamalloae sp. nov.], antennal tubercles not close, from antennomere VI [add ( VII) to cater for I. martinsi sp. nov.] more or less distinctly serrate. Prothorax, nearly always [usually would be better since that of I. ichneumoniformis is quadrate] longer than wide, broadly constricted at front, less behind; pronotal disc shining, with five calli, which may be vestigial. Elytra long [elytra of I. planifrons are short], reaching about as far as middle to apex of urosternite II [change to as far as apex of urosternite I to basal third of III, as in I. planifrons and I. laevicollis respectively], but never further; awl-shaped [or wedge-shaped as in I. planifrons ]; apices almost always rounded and truncate [see below]. Wings cover abdomen, frequently dusky, as a rule with pale, preapical fascia, or entirely translucent [delete with dusky fascia for clarity, and to cater for I. zamalloae sp. nov. with entirely translucent wings]. Procoxae globate and conical, cavities closed behind. Metasternum tumid and wider than base of abdomen, mesal margin of metepisterna narrowed to apex. Metafemora shorter than abdomen; metatibia not hirsute [better metatibia usually densely setose, never with compact brush]; metatarsi normal or thickened, tarsomere I [add usually to cater for I. zamalloae ] longer than II + III. Abdominal process (between metacoxae) either unicolourous, short and triangular, or [remove whitish, to end, to cater for male I. planifrons ], narrowed, curved and acuminate to apex [most of process, or only apex, may be whitish].

Male: Inferior lobes of eyes almost contiguous, or more distant; sides of prothorax with sexual puncturation; shape of urosternite V different from other abdominal segments.

Female: Inferior lobes of eyes well separated; sides of prothorax without sexual puncturation; urosternite V elongate and conical.

And, as Zajciw and many other authors have pointed out, members of the genus have a striking similarity to wasps of the families Braconidae and Ichneumonidae .

Discussion: It is not clear what Zajciw meant when he described the apices of the elytra as rounded-truncate; he used this term to describe the apices of I. cylindrica , I. rubra and I. planifrons and certainly, if we look at the figure he provided for I. cylindrica , the term is apt, but not at all typical of other species, I. planifrons included.

It seems necessary to re-word this part of the generic description because the shape of elytral apex is an important character for separating the species. Before doing so, another inter-specific character of use (which affects shape of elytral apices, and which Zajciw refers to without defining it) is, what will be referred to as, the humero-apical costa (the dorsal costa of other authors). The humero-apical costa, in its uninterrupted condition, can be described as the longitudinal convexity separating elytral disc from epipleuron, running from the most elevated part of humerus (where it is broad) to apex of elytra (where it is narrow and usually elevated). In I. martinsi sp. nov. it is complete, giving elytra a distinctly convex appearance; I. zamalloae sp. nov. slightly flattened behind humeri, otherwise complete; I. ichneumoniformis and I. laevicollis somewhat evanescent for middle third; and in I. planifrons only present for apical half, giving elytra a distinctly flat appearance.

If I. martinsi sp. nov. and I. planifrons represent the two extremes of the genus, the generic description of the sides and apices of elytra may be described as follows: humero-apical costa of elytra variable, from entire to partly evanescent, but always discernable towards apex; apical margins either rounded, or transversely to obliquely truncate (sometimes with spines or teeth at sides), or sharply acuminate.

A number of characters common to all the Bolivian species are: mandibles yellow with black tip (except I. planifrons entirely black); clypeus impunctate; antennae rather uniform; scape and pedicel smooth and shining (except male I. zamalloae sp. nov. slightly reticulate) with scattered punctures, antennomere III-V (less often to VI) setose mesally, closely punctured, rest micropunctate with very short dense pubescence; VI-X ( VII-X in I. martinsi sp. nov.) incrementally thickened and serrate at apex, XI acuminate at apex; legs increasingly longer from front to back.