Acanthosomatidae

Signoret, 1864

Shield Bugs

Genus Guides

Cyphostethus
Elasmostethus(Birch shieldbug)
Elasmucha(Parent shieldbugs)

is a of shield bugs within Pentatomoidea comprising approximately 200 in 55 across three (Acanthosomatinae, Blaudusinae, Ditomotarsinae). The family is notable for its distinctive reproductive , with females exhibiting either maternal care (-nymph guarding) or egg smearing using secretions from Pendergrast's organs. Maternal care has evolved independently at least three times within the subfamily Acanthosomatinae and is correlated with reduction or loss of Pendergrast's organs, suggesting an evolutionary trade-off between these strategies.

Elasmostethus interstinctus by (c) Andrew Meeds, some rights reserved (CC BY), uploaded by Andrew Meeds. Used under a CC-BY license.

Elasmostethus cruciatus by (c) Judy Gallagher, some rights reserved (CC BY). Used under a CC-BY license.

Elasmostethus cruciatus by (c) Fyn Kynd, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Acanthosomatidae: //əˌkænθoʊsoʊməˈtaɪdiː//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

can be distinguished from the similar Pentatomidae (stink bugs) by several morphological features: are keeled laterally with five-segmented ; the mesosternum possesses a strongly projecting keel; are bisegmented (two-segmented) rather than the three-segmented tarsi typical of most pentatomids; the second visible abdominal sternite bears an elongate spine projecting forward; of the second abdominal segment are concealed by the metapleura; and abdominal sternite III has paired . Males have exposed sternite VIII with a specialized genital capsule; females possess one or two pairs of Pendergrast's organs on the (absent in some such as Elasmucha) and sternite VII has an margin.

Images

Habitat

Arboreal; associated with trees and shrubs, particularly developing fruits of conifers and flowering plants. occupy diverse environments from high-latitude temperate regions to subtropical high-altitude zones.

Distribution

Worldwide distribution with Gondwanan origin. Greatest abundance in high-latitude temperate regions and subtropical regions at high altitudes. Approximately 80% of distributed in fragmented landmasses of Gondwana. Highest in East, South, and Southeast Asia within the Acanthosomatinae. Notable records include Chile (Maule Region to Magallanes Region), Brazil, southern tip of South America (Cabo de Hornos Reserve on Navarino Island), Tierra del Fuego, Europe, and northern Siberia.

Diet

Oligo- or herbivores feeding on developing fruits of conifers and flowering plants. Documented plants include Ficus, Hakea, Carex, Juncus, Cladium, Dactylis, hawthorn (Crataegus), rowan (Sorbus), cherry (Prunus), and Nothofagus dombeyi. Some records of (including ) and scavenging on carrion exist but are not primary feeding modes.

Host Associations

Nothofagus dombeyi - plantFirst plant record for Acrophyma cumingii

Life Cycle

Females in maternal care attend and nymphs until the 2nd to 5th instar. In non-caring species, females smear eggs with secretions from Pendergrast's organs using their hind legs before abandoning the clutch; egg smearing represents the ancestral condition. Clutch size, egg size, and developmental periods vary among species; no maternal care observed in Japanese Elasmostethus species studied.

Behavior

Two distinct reproductive strategies: (1) maternal care involving physical guarding of and nymphs against with defensive movements, sometimes including joint guarding and effective resource allocation among eggs; (2) egg smearing with Pendergrast's organ secretions as chemical protection before female departure. Maternal care has evolved independently at least three times in Acanthosomatinae (Elasmucha, Sastragala, Acanthosoma firmatum) and once in Sinopla perpunctatus. No secondary loss of maternal care has been detected, possibly because the PO-free condition creates vulnerability that maintains care once evolved.

Ecological Role

Herbivores on developing fruits of conifers and flowering plants. Maternal guarding provides defensive function against and . Prey for specialized predators including sand wasps in the Bicyrtes, which hunt shield bug nymphs as food for their larval offspring.

Human Relevance

Includes economically notable such as the hawthorn shield bug (Acanthosoma haemorrhoidale), a widespread European species. Some species serve as biocontrol targets due to their herbivory on cultivated plants. The has been used in behavioral research on the evolution of maternal care and reproductive strategies. New species descriptions from remote regions (e.g., Planois smaug from Patagonia) highlight conservation value of pristine .

Similar Taxa

PentatomidaeSimilar shield-like body form; distinguished by tarsal segmentation (three-segmented in most pentatomids versus two-segmented in acanthosomatids), though some pentatomids also have bisegmented requiring examination of additional characters
ScutelleridaeBoth include shield bugs; Bicyrtes sand wasps prey on both groups, indicating ecological overlap

More Details

Evolutionary biology significance

represents an important model system for studying the evolution of maternal care and correlated trait evolution. Molecular phylogenetic studies demonstrate that maternal care is an apomorphic trait arising multiple times from the ancestral -smearing condition, with strong statistical correlation between care and reduction/loss of Pendergrast's organs suggesting physiological trade-offs.

Subfamily classification

Three recognized: Acanthosomatinae (majority of diversity including maternal care lineages), Blaudusinae ( Hiarchas, Xosa), and Ditomotarsinae (genus Uhlunga, plus Patagonian genera such as Hyperbius).