Pachynomidae is a family of true bugs within the suborder Cimicomorpha. 23 species in 5 genera are known.
Morphology.
Pachynomidae range in size from 3.5 to 11 millimetres and often bear a certain resemblance to sickle bugs (Nabidae) from the subfamily Prostemmatinae. The upper surface of their bodies varies from very shiny (genus "Pachynomus" ) to matte and hairless to heavily hairy. The compound eyes are large, and the head has no constriction behind the compound eyes. Ocelli can be present or absent. The antennae appear to have five segments, with the second segment (pedicellus) divided into two parts. The distal part of the pedicellus usually bears a single trichobothrium. The labium is thick and strongly curved. The thighs (femora ) of the forelegs are greatly enlarged, and the shins (tibiae) of the forelegs bear "fossulae spongiosae" (specialised hairy structures used for holding on). The eighth abdominal segment of the males is reduced and retracted into the seventh segment. Male genitalia are symmetrical, the pygophore is well developed and apically articulated into the abdomen. The ovipositor of the females is plate-shaped. A spermatheca is missing, but a pseudospermatheca is present.
Biology.
The biology of Pachynomidae is poorly known. Museums contain only few samples of Pachynomidae, as they are often confused with Nabidae or Reduviidae. It is possible that Pachynomidae are noctural ground-dwelling predators, as they are often collected from leaf litter or light traps. Immature forms are not known for most genera, with the exception of "Aphelonotus".
Few species seem to show sexual dimorphism; it has been described in the genera "Aphelonotus" and "Camarochilus". Some species show wing dimorphism; it is known in "Aphelonotus simplus" males and "Camarochilus americanus" females, while the species "Camarochiloides weiweii" presents both brachypterous and macropterous morphs across sexes.
Taxonomy.
The current genus "Pachynomus" was considered a subgenus of the genus "Reduvius" by its first describer Klug in 1830. Carl Stål placed it and the genus "Punctius" in Nabidae, where they remained, confirmed by many subsequent authors (with the exception of Reuter 1908), until Carayon elevated the group to family rank in 1950. He considered the family to be most closely related to the assassin bugs (Reduviidae) due to the characteristics of the reproductive organs. Analysis of the mitochondrial genome recovered them as the sister group of Reduviidae.
The family includes the following subfamilies and genera:
Subfamily Aphelonotinae
Genus "Aphelonotus" (tropical America, Central Africa)
Subfamily Pachynominae
Genus "Camarochilus" (tropics of the New World)
Genus "Camarochiloides" (Old World)
Genus "Pachynomus" (Africa to India)
Genus "Punctius" (Africa to India)