Host–Parasite Interactions between Mites (Acari: Erythraeidae) and Harvestmen (Opiliones, Eupnoi) as Indicators of Habitat Quality in the Atlantic Forest

Parasitism is a key ecological interaction shaping arthropod communities, yet the influence of habitat quality on these relationships remains underexplored. Larvae of the genus Leptus (Erythraeidae) are widespread ectoparasites of arthropods, including harvestmen. We investigated the association between Leptus larvae and two Eupnoi harvestmen—Munequita pulchra Mello-Leitão, 1941 and Jussara rosea (Mello-Leitão, 1940)—in a continuous fragment of Atlantic Forest, evaluating how structural vegetation attributes influence infestation prevalence and intensity. We hypothesize that mite parasitism intensity increases in disturbed habitats due to reduced vegetation complexity and associated changes in microclimatic conditions that favor parasite development.. We sampled 146 individuals (110 M. pulchra, 36 J. rosea), recording 102 ectoparasites. Prevalence was higher in M. pulchra (29%) than in J. rosea (5%), with about 70% of mites attached to the femora of legs I–IV. Infestation intensity varies with host species and environmental conditions. Principal Component Analysis revealed vegetation gradients linked to forest age and structural complexity, negatively correlated with M. pulchra abundance and positively with J. rosea. Statistical models identified canopy cover, litter depth, and the first principal component as the strongest predictors of parasitism intensity in M. pulchra. Our findings indicate that structurally simplified forests favor generalist harvestmen and higher parasite loads, highlighting the importance of maintaining complex Atlantic Forest habitats to conserve arthropod diversity and ecological processes.