Mandibles and labrum-epipharynx of tiger beetles: basic structure and evolution (Coleoptera, Carabidae, Cicindelitae)

Area of Science:

• Entomology
• Evolutionary Biology
• Morphology

Background:

• The study focuses on the supertribe Cicindelitae (tiger beetles) and related basal geadephagans.
• Understanding the evolution of mandibles and labrum-epipharynx is crucial for insect phylogeny.

Purpose of the Study:

• To describe and illustrate the mandibles and labrum-epipharynx of basal geadephagans for comparison with Cicindelitae.
• To assess the variation and evolutionary patterns of these structures within Cicindelitae.
• To postulate an evolutionary transformation series for the mandibles and labrum-epipharynx.

Main Methods:

• Scanning electron microscopy (SEM) was used to image mandibular and labrum-epipharyngeal structures.
• Morphological and DNA evidence were utilized to reconstruct phylogenetic sequences.
• Comparative analysis of nine exemplar taxa within Cicindelitae and three outgroup taxa.

Main Results:

• Detailed descriptions and illustrations of mandibles and labrum-epipharynx in Trachypachus gibbsii, Pelophila rudis, and Ceroglossus chilensis.
• Identified key evolutionary changes in mandibles, including setation, retinaculum, terebra, diastema, and scrobal structures.
• Documented evolutionary transformations in the labrum (form, setae) and epipharynx (pedium, setae orientation and number).

Conclusions:

• A comprehensive evolutionary transformation series for the mandibles and labrum-epipharynx was postulated for Cicindelitae.
• The study provides a framework for understanding the evolution of these critical feeding and sensory structures in ground beetles.
• The findings contribute to the broader understanding of insect evolution and phylogeny.