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RESEARCH PRODUCT

Tibial combs in the Cydnidae (Hemiptera: Heteroptera) and their functional, taxonomic and phylogenetic significance

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description

Tibial combs in representatives of the family Cydnidae are described in detail for the first time. The structure was studied in 98 species of 58 genera representing all the subfamilies, among them 16 species were investigated using scanning electron microscopic (SEM) techniques. In addition, Parastrachia japonensis (Scott, 1880) of the family Parastrachiidae, and two species of Dismegistus Amyot and Serville, 1843 (a genus of uncertain systematic position within Pentatomoidea) have also been studied. Morphological terminology is proposed for all the structures connected with tibial combs and the term ‘the tibial comb complex’ is suggested; its functional, taxonomic and phylogenetic significance is also discussed. The genera of Cydnidae can be classified into two groups depending on differences in the tibial comb complex, when it is present; moreover, its absence in the tribe Scaptocorini (Cephalocteinae) is demonstrated for the first time and is regarded as an autapomorphy of this tribe. Data on the occurrence of tibial combs in other families of true bugs (Hemiptera: Heteroptera) are also briefly reviewed, and an anagenetic trend in their evolution in terrestrial Heteroptera is hypothesized. The presence of tibial combs on all legs is regarded as the most plesiomorphic state. Resume Les peignes tibiaux des Cydnidae sont decrits en detail pour la premiere fois chez 98 especes appartenant a 58 genre representant toutes les sous-familles; seize especes ont ete examinees au microscope electronique (MEB). De plus, les especes de deux genres dont la position systematique reste incertaine, Dismegistus Amyot et Serville, 1843 and Parastrachia Distant, 1880, ont eteetudiees. Une terminologie est proposee pour toutes les structures associees au peigne tibial, ces structures formant un ensemble que l'on peut designer sous les termes de «complexe du peigne tibial». Les significations fonctionnelle, taxonomique et phylogenetique de ces structures sont aussi discutees. Les genres de Cydnides peuvent etre repartis en deux groupes selon les differences constatees au niveau de ces structures; l'absence de peigne tibial chez les Scaptocorini (Cephalocteinae), mis ici en evidence pour la premiere fois, peut etre consideree comme une autapomorphie de cette tribu. Les donnees sur la repartition des peignes tibiaux dans les autres familles d'Heteropteres sont egalement brievement reexaminees et des hypotheses sont avancees sur les tendances anagenetiques de ces structures au cours de l’evolution des Heteropteres terrestres. La presence de peignes tibiaux a toutes les pattes est considere comme l’etat le plus plesiomorphe.