Morphology of the external scent efferent system of Neotropical shield bugs (Hemiptera: Scutelleridae: Pachycorinae)

Abstract

The metathoracic scent glands are characteristic of the true bug suborder Heteroptera and are known to have defensive, sexual and aggregation roles, among others. The morphology of external scent efferent system (ESES) associated with these glands has taxonomic and phylogenetic importance. These structures have been documented previously in four of the eight Scutelleridae subfamilies. In this work we investigate them in detail in 22 genera of the New World subfamily Pachycorinae using scanning electron microscopy. We report five general types of ESES in pachycorine: (1) enlarged evaporatorium and well-developed peritreme; (2) well-developed evaporatorium and poorly developed or obsolete peritreme; (3) reduced evaporatorium and small or obsolete peritreme; (4) reduced evaporatorium on mesepimeron and elongate peritreme; (5) enlarged evaporatorium and elongate peritreme. Our results are in contradistinction to previous accounts of the ESES for the Pachycorinae which have been reported as being poorly developed. The Pachycorinae patterns do not support Schaefer’s hypothesis that there is a correlation between degree of development of the external metathoracic structures and way of life. We also demonstrate that these structures are of systematic importance in the Pachycorinae.