Acanthosomatidae is a family of Hemiptera, commonly named "shield bugs" or "stink bugs". Kumar in his 1974 world revision recognized 47 genera; now this number is 55 genera, with about 200 species, and it is one of the least diverse families within Pentatomoidea. The Acanthosomatidae species are found throughout the world, being most abundant in high-latitude temperate regions and in subtropical regions at high altitudes.
One of the most well-known species in Acanthosomatidae is the hawthorn shield bug (Acanthosoma haemorrhoidale), which is found throughout Europe and also northern Siberia; this species is typically green or brown in color and has a distinctive shape with two projections on its thorax. It feeds on a variety of plants, including hawthorn, rowan, and cherry.
Description
Acanthosomatidae have heads that are keeled laterally and possess a pair of 5-segmented antennae. The mesosternum has a strongly projecting keel. The tarsi of the legs are 2-segmented. The second visible abdominal sternite has an elongate spine that projects forwards. The spiracles of the second abdominal segment are concealed by the metapleura. Abdominal sternite III has paired trichobothria. In males, sternite VIII is exposed and there is a specialised genital capsule. In females, one or two pairs of Pendergrast's organs are present in the abdomen (sometimes absent, e.g. Elasmucha) and sternite VII has an emarginate posterior margin.
In general appearance, Acanthosomatidae are similar to Pentatomidae. Various sources distinguish them based on the number of tarsal segments being 2 in acanthosomatids and 3 in pentatomids. However, some pentatomids have 2-segmented tarsi as well.
Ecology
Acanthosomatidae are mostly herbivores on trees and shrubs. Host plants include Ficus, Hakea, Carex, Juncus, Cladium and Dactylis. There are also records of predation (including cannibalism) and scavenging on carrion.
Maternal care
Many species have females which take care of their offspring, guarding the eggs and nymphs. In these species, the Pendergrast's organs are absent or reduced and non-functional. Other species have a more limited form of care: females smear their eggs with secretions from the Pendergrast's organs (which may repel predators and parasitoids), then abandon the eggs. Egg smearing is the ancestral behaviour.
Genera
Examples of genera and species: Acanthosoma Curtis, 1824 Acanthosoma haemorrhoidale (Linnaeus, 1758) — Hawthorn shield bug Acanthosoma labiduroides Jakovlev, 1880 — Green shield bug Cyphostethus Fieber, 1860 Cyphostethus tristriatus — Juniper shield bug Elasmostethus Fieber, 1860 Elasmostethus interstinctus — Birch shield bug Elasmostethus minor Elasmucha Stål, 1864 Elasmucha cordillera Thomas, 1991 Elasmucha ferrugata (Fabricius, 1787) Elasmucha fieberi (Jakovlev, 1864) Elasmucha flammatum (Distant, 1893) Elasmucha grisea (Linnaeus, 1758) — Parent bug Elasmucha lateralis (Say, 1831) Eupolemus Oncacontias Breddin, 1903 Oncacontias vittatus — Forest shield bug