Parasitoid phorid flies of leaf‐cutting ants are negatively affected by loss of forest cover

Habitat fragmentation can have a high impact on parasitoid–ant interactions. Phorid flies are among the most important groups of natural enemies of leaf‐cutting ants. We studied the effects of loss in forest cover upon phorids of the leaf‐cutting ant Acromyrmex nigerSmith (Hymenoptera: Formicidae: Attini) in a fragmented area in the Southeastern Atlantic Forest, Brazil. We sampled 10 forest fragments, five large (>75 ha) and five small (<20 ha), as well as three areas of continuous forest (>1 000 ha). We marked 1–5 colonies of A. niger in the interior of each forest location. At each nest, we collected all of the phorids in interaction with the worker ants for a period of 15 min. We then collected ca. 200 worker ants, which we maintained in the laboratory for rearing phorids from them. We identified three phorid genera – Apocephalus, Myrmosicarius, and Neodohrniphora – which we both observed in the field and reared in the laboratory. The abundance and parasitism percentage were significantly greater in continuous forest sites than in forest fragments, whereas there were no significant differences between fragments of different sizes. These results provide further evidence for the effects of habitat size on the phorid‐Acromyrmex system in a tropical rain forest, based on the abundance of parasitoids both as adults in the field and as reared immature phorids in the laboratory.