Parastizopus armaticeps armaticeps (Péringuey 1892)
P. armaticeps is a medium-sized flightless shiny black beetle measuring 15 mm. It belongs to a genus characterized by the plain elytral base (without border), relatively large and oblong body, the presence of elytral rows. Median part of mentum wide, moderately convex, without longitudinal carina; prosternal process projecting posteriad.
P. armaticeps: Anterior margin of head with moderately deep clypeal emargination, base of labrum not visible; surface of the abdominal ventrites covered with punctures. Elytral humeri moderately obtuse, slightly produced anteriad. Fore and mid tibiae in both sexes with sharp or obtuse edge at apex.
Original description in:
Péringuey, L. 1892. Fourth contribution to the South African coleopterous fauna. Description of new Coleoptera in the South African Museum. Transactions of the South African Philosophical Society, 6
https://www.biodiversitylibrary.org/item/113571#page/220/mode/1up
Black, moderately shining, hairless; head punctulated with a deep transverse impression, epistome arcuated, incised in the centre with two sharp short spines on each side of the dent; prothorax with the sides rounded and the anterior half broader than the posterior, finely punctured, depressed; elytra less broad than the prothorax, nearly parallel, rounded behind, depressed and finely striated; anterior tibiae broadly dilated at the apex, and with an obtuse tooth inwardly, the intermediate and posterior acutely rugose, dilated at the apex with a sharp tooth outside and a blunt one inside, the posterior ones are also sub-falcate.
The species is distributed throughout the Kalahari dune system and inhabits semi-stable and stable dune faces. In the southern Kalahari it is closely associated with its food plant Calobota linearifolia, the fallen leaves and twigs of which are staple diet for adults and larvae.
Subsociality involving biparental care has been extensively studied in this species in the Kalahari. Parental investment in a very small number of offspring is a response to rapid sand desiccation and food scarcity. The beetles dig aggregated burrows in the sand after rains in the vicinity of Gannabushes. Only slight modification of these burrows can take place once the sand is dry, owing to its friability and the likelihood of burrows collapsing. During drought, therefore, beetles are dependent on already existing burrows. Long-term pair bonds are formed, the beetles digging breeding burrows into which females bring food after foraging at night. The adoption of a nocturnal lifestyle allows P. armaticeps to escape high daytime surface sand temperatures. Both parents care for the young and excavate a breeding burrow together. They play similar roles in burrow excavation and protection until the eggs hatch, after which male and female roles diverge markedly. Females collect detritus on the surface at night, depositing this at the burrow entrance, which they also clear of sand in the early evening. Males remain inside the burrow and dig to deepen and extend it, maintaining its moisture level as the sand desiccates. They also pull the food dropped by the female down to the burrow base to form a food store for the offspring. Both sexes guard the burrow and attack same-sex intruders, especially in the early phases of reproduction. The parents remain inside with the pupal cocoons until the teneral adults eclose.
Breeding success depends primarily on male size because larger males dig deeper burrows which remain moist longer to favor larval development, and females select the largest male partners by pushing under them to judge their weight. Parastizopus beetles are also unique among tenebrionids in terms of an extraordinary courtship behavior. After heavy rainfalls, the beetles emerge from aggregation burrows, which they inhabit during drought, and court in small mixed-sex groups on the ground surface. Females select their partners among the males present based on male body mass, which indicates the digging ability of a male. The courting groups are initiated by males, which exhibit a characteristic calling behavior: Males do a headstand and expose their aedeagus emitting a pheromone that attracts females.
iNat observation: https://www.inaturalist.org/observations/36878773
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