Acanthosomatidae

Acanthosomatidae
	Acanthosomatidae - relative sizes
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hemiptera
Suborder:	Heteroptera
Superfamily:	Pentatomoidea
Family:	Acanthosomatidae; Signoret, 1864
Subfamilies
	Acanthosomatinae; Blaudusinae; Ditomotarsinae

Acanthosomatidae is a family of Hemiptera, commonly named "shield bugs" or "stink bugs". Kumar in his 1974 world revision recognized 47 genera;^[1] now this number is 55 genera, with about 200 species, and it is one of the least diverse families within Pentatomoidea.^[2]^[3] The Acanthosomatidae species are found throughout the world, being most abundant in high-latitude temperate regions and in subtropical regions at high altitudes.^[4]

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^[4]) and sternite VII has an emarginate posterior margin.^[5]

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.^[6]^[7] However, some pentatomids have 2-segmented tarsi as well.^[8]

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.^[5]

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.^[9]