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Pachylis argentinus

Pachylis argentinus


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

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Records from Argentina


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

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Foto
Photography ID: 436869
  Nymph

Ingeniero Maschwitz
Buenos Aires
Argentina
03/13/2021
Guillermo F Negrete



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Page 1
Record IDDateExact timeCountryProvince / departmentPlaceFilmedPhotographedRecorded vocalObservedHeardWounded or deadNumber of individualsUser or BibliographyDetail
137840813/03/2021ArgentinaBuenos AiresIngeniero MaschwitzGuillermo F Negrete
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 01/10/2026.