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Entomophthoralean fungi with pathogenic abilities to infect social insects are rare. Here, we describe a fungus isolated from leafcutter ants. Morphologically, the fungus has spherical primary conidia and two types of microconidia: one with the same shape as the primary conidia and another with an elliptical to half-moon shape. The fungus also produces villose conidia known previously only from Conidiobolus coronatus. A multilocus phylogenetic analysis was performed with nuc rDNA sequences from three regions (28S, 18S, and internal transcribed spacer [ITS]). Our isolates are distinguished as a new species, described here as Conidiobolus lunulus, and is more closely related to C. brefeldianus than to C. coronatus, despite the greater morphological resemblance to the latter. Morphological differences, unique phylogenetic placement, and isolation from an altogether new host support this finding. This is the first record of an entomophthoralean species isolated from leafcutter ants.

Myrmecophytic Cecropia trees feed and house ants, presumably in exchange for protection from herbivory. These plants produce ant rewards in the form of Mullerian bodies (MB), glycogen-rich and protein-containing corpuscles located on trichilia at the bases of leaf petioles. Because of indirect evidence for the costliness of MB, we conducted experiments to determine whether plants respond to their removal (simulating the presence of ants) and accumulation (imitating the absence of ants) by altering rates of their production. In greenhouse experiments with plants cultivated at intermediate nutrient levels, MB production rates were significantly higher on plants from which the MB were removed than on control (MB accumulation) plants (...)