Morphology of the abdominal sternal stridulitrum and tibial plectrum in Pachycorinae (Hemiptera: Heteroptera: Scutelleridae).

The presence of the stridulatory structures has been empirically used as a diagnostic character for Pachycorinae, but it is also present in Hoteinae and two genera of Odontotarsinae. The stridulitrum is present mostly on sternites V–VI in Scutelleridae, associated with a plectrum on the hind tibiae. These structures have been recently analysed under scanning electron microscopy (SEM); however, only 9 of the 27 Pachycorinae genera were examined; moreover, the tibial plectra were not examined. In this work, we investigated the stridulatory device of 26 genera of Pachycorinae. The morphology of these structures was examined and described under light stereomicroscope and SEM. We report two patterns of stridulitrum: (1) smooth carinae, found in 24 genera; (2) coarse carinae, composed of many small teeth similar in size, found in 3 genera. Two main patterns were found regarding the tibial plectra: (1) rounded tubercles that were conspicuous in 3 genera and inconspicuous in 23 genera; (2) flat tubercles found in 2 genera. Our results demonstrate that the stridulatory devices have taxonomic significance within Pachycorinae and should be considered in further studies. [ABSTRACT FROM AUTHOR]