Dissomphalus microstictus, Evans, 1969

Alencar, I. D. C. C. & Azevedo, C. O., 2008, A new species-group of Dissomphalus (Hymenoptera: Bethylidae), with description of thirteen new species, Zootaxa 1851 (1), pp. 1-28 : 2-3

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https://doi.org/ 10.11646/zootaxa.1851.1.1

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scientific name

Dissomphalus microstictus


microstictus species-group

Diagnosis: male. Clypeus with trapezoidal median lobe ( Fig. 2 View FIGURES 1–8 ); apex of ventral ramus of aedeagus with latero-apical filament ( Fig. 4 View FIGURES 1–8 ). Female: mandible tetradentate with subupper tooth smaller than uppermost one ( Fig. 98 View FIGURES 90–102 ); clypeus with median lobe rounded, mid part elevated and thick in frontal view ( Fig. 99 View FIGURES 90–102 ).

Comments: the microstictus species-group comprises 14 species: D. balteus , D. divaricatus , D. forceps , D. incurvatus , D. osseus , D. paululus , D. perparvus , D. perturbatus , D. perventriosus , D. pilus , D. refertus , D. signatus , and D. uncus , in addition to D. microstictus .

The latero-apical filament of the ventral ramus of the aedeagus is proposed as a diagnostic feature for the microstictus species-group rather than only for D. microstictus . Unlike most of the species-groups in Dissomphalus , the microstictus species-group is diagnosed by the shape of the genitalia. The large intra- and interspecific variation of the tergal processes in the D. microstictus species-group, varying from absent to conspicuous ( Figs. 3 View FIGURES 1–8 , 12–16 View FIGURES 9–16 , 90 View FIGURES 90–102 ), makes this character inadequate as a diagnostic character for species-group level.

Dissomphalus xanthopus has a filament in the ventral ramus, like species in the microstictus speciesgroup. But D. xanthopus has the filament near to the inner margin of the ventral ramus, located in the middle of the ramus (see Fig. 19 View FIGURES 17–27 in Azevedo 1999b), whereas species in the microstictus species-group have the filament near to the outer margin of ventral ramus and located apically in the ramus ( Fig. 4 View FIGURES 1–8 ).

The mandible of the species of the microstictus species-group can have two or three apical teeth. The number does not vary within each species, but D. microstictus and D. perventriosus have specimens with mandible bi- or tridentate. The number of mandibular teeth varies in many other species such as: D. differens Redighieri & Azevedo , D. distans Redighieri & Azevedo , D. infissus Evans , D. laminaris Redighieri & Azevedo , D. lobicephalus Azevedo , D. setosus Redighieri & Azevedo , and D. spissus Redighieri & Azevedo. Future keys for Dissomphalus should consider this intraspecific variation.

The tergal process (having a pit only or a pitted tubercle) also varies within species as discussed above. Some specimens of the microstictus species-group potentially could be misidentified as belonging to the conicus group. Members of this species-group have tergal processes with conspicuous pitted tubercles bearing tufts of setae. The same occurs to D. connubialis Evans , as discussed by Redighieri & Azevedo (2006), when they suggest D. connubialis as a possible member of the conicus species-group. Every species included in the conicus group has tuft densely setose justifying D. connubialis as a member of this group. Differing from the conicus group, the species in the microstictus species-group have tubercle always with none or only with few short setae mesad. Besides, many specimens of the species of the microstictus species-group have the tubercle with a pit on top and the anterior margin of the depression with conspicuous setae resembling the specimens of the setosus species-group. Furthermore, at least some specimens of D. balteus , D. perventriosus , D. microstictus , and D. divaricatus have tergal process completely absent. Such intraspecific variation is also found within others groups and species, such as D. incomptus Evans and D. microtuberculatus Azevedo.

The metasomal tergites of the specimens studied here seem to have a characteristic pattern: a w-area in the middle of each tergite is lighter or darker than laterally ( Fig. 16 View FIGURES 9–16 ). This pattern is better seen in specimens without tergal process, as well as in specimens with lighter color on the metasoma.

The paramere of the species analyzed in this study is bilaminar basally ( Fig. 89 View FIGURES 78–89 ), but this condition has also been observed for other Dissomphalus species , such as D. coronatus Alencar & Azevedo , D. excellens Redighiri & Azevedo , D. fungosus Evans and D. napo Evans.

Etymology: refers to the oldest species of this group.

Distribution: Panama, Venezuela, Trinidad and Tobago, Brazil, Ecuador, Peru, Bolivia and Argentina.