Plan of Sulfur Cave, with depiction of the main sulfidic springs (blue areas), and the large spider web in the vicinity of the cave entrance (brown areas) (modified from Audy et al. 2022 and Sarbu et al. 2024).

The colonial spider web in Sulfur Cave, is home to a mixed colony of Tegenaria domestica and Prinerigone vagans. A. Side view; B. frontal view. The swarm of adult chironomids is visible near the cave stream. Photo A: Marek Audy.

Tegenaria domestica in Sulfur Cave. A Female next to a funnel shaped hole in the colonial spider web. B Female epigyne. C Male pedipalp with retrolateral view.

Prinerigone vagans in Sulfur Cave. Male and male pedipalp (right). Female and female epigyne (left).

Haplotype networks of COI sequences for four spider species from Sulfur Cave separated into individual panels A Tegenaria domestica B Kryptonesticus eremita C Prinerigone vagans D Metellina merianae. The haplotypes from Sulfur Cave are shown in yellow. The circle size is proportional to the number of sequences in each haplotype and the number of mutations between haplotypes are denoted by hash marks.

Monthly variation in the number of eggs per egg sac in Tegenaria domestica.

Mean (+ standard deviation) of δ¹³C and δ¹⁵N values of four spider species (Tegenaria domestica, Metellina merianae, Prinerigone vagans, Lepthyphantes magnesiae, Araneae), their potential food resource (the non-biting midge Tanytarsus albisutus) and the basal food resource (biofilm) of the cave food web in Sulfur Cave located at the border between Albania and Greece (animal drawings by Svenja Meyer). ‘Surface spiders’ include representatives of the families Lycosidae, Salticidae, and Pholcidae.

Comparison of the Shannon diversity index of the microbiome of the opisthosoma of one surface individual of Tegenaria domestica caught near Pixaria Cave vs. 29 individuals of the same species from Sulfur Cave (three Sulfur Cave individuals with insufficient number of reads were excluded from the analysis). S0 individuals were caught at the entrance of Sulfur Cave, S1 on the first section of the spider wall and S2 and the second section.

Metellina merianae. Female (left) and male (right) in individual webs on the cave wall.