Description of a new Eukoenenia (Palpigradi: Eukoeneniidae) and Metagonia (Araneae: Pholcidae) from Brazilian caves, with notes on their ecological interactions

Palpigradi comprises the most poorly known order within the Arachnida; hence, information regarding their biology and behavior is quite scarce. We document an interaction between a palpigrade of the genus Eukoenenia being preyed upon by a spider of the genus Metagonia in the Gruta do Vale, a cave in the municipal district of Felipe Guerra (Rio Grande do Norte, Brazil). The entire prey recognition and capture process by the Metagonia is described in full detail. Both species involved, Eukoenenia potiguar n. sp. and Metagonia potiguar n. sp., are also described. Metagonia potiguar n. sp. is the first Brazilian cave-dwelling Metagonia to be described.