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Pachylis argentinus

Pachylis argentinus


Family: Coreidae
Order: Hemiptera
Class: Insecta
Phylum / Division: Arthropoda
Kingdom: Animalia

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Description


Characterized by its robust and imposing physical build, this terrestrial hemipteran exhibits a predominantly dark brown to blackish coloration with ferruginous undertones. Adults typically measure between 20 and 28 millimeters in length. The most diagnostic morphological feature is the prominent foliaceous expansion on the hind tibiae, which resembles a dried leaf and is highly characteristic of the family Coreidae. Sexual dimorphism is starkly pronounced; males possess exceptionally swollen hind femora armed with distinct spines and tubercles on the ventral surface, which are utilized in intraspecific combats. The antennae are segmented into four parts, with the terminal segment often displaying a contrasting bright yellow or orange coloration. The pronotal margins are slightly serrated, sometimes bordered by a subtle pale transverse line.

Geographical distribution: This species is widely distributed throughout the Southern Cone of South America, with well-documented populations in Argentina (extending from northern provinces down to northern Patagonia), Uruguay, Paraguay, southern Bolivia, and the southern states of Brazil. It occupies major biogeographic regions such as the Humid Chaco, Dry Chaco, Espinal, and the Pampean grasslands.

Habitat: It primarily colonizes xerophytic woodlands, shrubby savannas, gallery forests, and scrublands. Due to its remarkable ecological plasticity, it has successfully adapted to disturbed habitats, agricultural lands, suburban parks, and urban gardens, provided its preferred host plants are present.

Feeding: It is a strictly phytophagous insect, specialized in sap-sucking. It feeds predominantly on woody plants within the Fabaceae family. Host plants include various species of the genera Acacia (most notably the espinillo Acacia caven), Prosopis (mesquites), and Parkinsonia. The insect employs its piercing-sucking mouthparts to penetrate young shoots, tender twigs, and green seed pods to extract nutrient-rich vascular fluids.

Behavior: It exhibits predominantly diurnal activity. During the nymphal stages, individuals display strong gregarious behavior, clustering in dense aggregations on host plant branches, which serves for thermoregulation and predator deterrence. Adults are generally more solitary and are clumsy, noisy flyers. When threatened, they employ chemical defense mechanisms, emitting a pungent, foul-smelling secretion synthesized in their metathoracic glands to repel potential predators.

Reproduction: The reproductive cycle begins with territorial behavior, where males defend prime feeding sites using their heavily armed hind legs to fight off rival males. Following copulation, the female deposits eggs in orderly, linear clusters directly onto the twigs or leaf surfaces of the host plant. The eggs are cylindrical and copper-toned. Development is paurometabolous, progressing through five nymphal instars. Early instars feature striking aposematic coloration with bright red and black patterns, warning predators of their unpalatability before achieving their final adult form.

Conservation status: It has not been assessed by the IUCN Red List (Not Evaluated). Thanks to its vast geographical range, high local abundance, and high tolerance for anthropogenic landscapes, its populations are currently stable, facing no significant threats of decline or extinction.



Compilation and publication: EcoRegistros – 01/10/2026




Geographic distribution


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Species photographs

Last published photographs

Foto
Photography ID: 414192
  Adult

Santa Fe
Santa Fe
Argentina
10/02/2020
Gustavo Fernando Durán
Foto
Photography ID: 414191
  Adult

Santa Fe
Santa Fe
Argentina
10/12/2020
Gustavo Fernando Durán
Foto
Photography ID: 101773
 
Santa Fe
Santa Fe
Argentina
10/19/2013
Gustavo Fernando Durán
Foto
Photography ID: 101768
  Nymph

Santa Fe
Santa Fe
Argentina
10/19/2013
Gustavo Fernando Durán
Foto
Photography ID: 101767
  Nymph

Santa Fe
Santa Fe
Argentina
10/19/2013
Gustavo Fernando Durán
Foto
Photography ID: 101678
♀
  Adult

Santa Fe
Santa Fe
Argentina
10/19/2013
Gustavo Fernando Durán



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Species reports



 Detail of places sorted by number of records








Page 1
Record IDDateExact timeCountryProvince / departmentPlaceFilmedPhotographedRecorded vocalObservedHeardWounded or deadNumber of individualsUser or BibliographyDetail
252908419/09/202608:47ArgentinaSanta Fe9 de Julio 749, Santa Fe de la Vera Cruz1Gustavo Fernando Durán
236968401/10/202513:05ArgentinaSanta FeAvenida Gobernador Freyre 1647, Santa Fe de la Vera Cruz1Gustavo Fernando Durán
236144017/09/202505:59ArgentinaSanta FeZona Sur, Santa Fe1Gustavo Fernando Durán
215246916/09/2024ArgentinaSanta FeAvenida de Circunvalación de Santa Fe, Santa Fe de la Vera Cruz1Gustavo Fernando Durán
200813814/02/2024ArgentinaSanta FeMuseo y Parque de la Constitución Nacional, Santa Fe1Gustavo Fernando Durán
189504011/10/2023ArgentinaSanta FeZona Sur, Santa Fe1Gustavo Fernando Durán
165500814/10/2022ArgentinaSanta FeZona Sur, Santa Fe1Gustavo Fernando Durán
146995701/10/2021ArgentinaSanta FeAvenida General López 3681, Santa Fe1Gustavo Fernando Durán
129810512/10/2020ArgentinaSanta FeSanta FeGustavo Fernando Durán
129810802/10/2020ArgentinaSanta FeSanta FeGustavo Fernando Durán
Page 1

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Recommended citation
Please use the following reference when citing this species account.
EcoRegistros. 2026. Pachylis argentinus – Species account. Accessed from www.ecoregistros.org on 03/10/2026.