Metathoracic glands and associated evaporatory structures in Reduvioidea (Heteroptera: Cimicomorpha), with observation on the mode of function of the metacoxal comb

Abstract

Structures that assist in spreading secretions produced by the metathoracic glands were examined in Reduviidae and Pachynomidae (Heteroptera). The systematic distribution of a row of long and stout setae on the metacoxa, the metacoxal comb, was reinvestigated in a representative sample in both taxa. Observations on living Dipetalogaster maximus (Reduviidae: Triatominae) corroborated the interpretation of this metacoxal comb as an evaporatory device, which assists in atomizing the gland secretions. In addition to the metacoxal comb, a row of stout setae on the metacetabolum - a metacetabular comb - was found in several Reduviidae, which interacts with the metacoxal comb during rotation of the metacoxa. In addition to those atomizing devices, cuticular modifications surrounding the opening of the metathoracic gland, which presumably form evaporatoria, were discovered in Ectrichodiinae. The meshwork-like structure of this cuticle resembles the cuticular modifications found associated with the opening of the Brindley's gland in Reduviidae, but differs from the mushroom-like evaporatoria around the metathoracic glands in most Cimicomorpha and Pentatomomorpha. Thus, two fundamentally different mechanisms to spread secretions of the metathoracic gland atomization and evaporation - are present in Reduviidae.