D3157: Mechanical mode of invasion of the fungus Cordyceps militaris on larvae of the painted lady butterfly, Vanessa cardui

Fungi serve as an important control agent that regulates insect population sizes. Fungi in the genus Cordyceps are particularly well known for their role in invading and overtaking the body of the insect. Here, we studied the mechanical mode of invasion of Cordyceps militaris, a species common to the northern hemisphere. We inoculated multiple second-instar larvae of the painted lady butterfly, Vanessa cardui, with C. militaris and then studied the external and internal anatomy of a larva with scanning electron microscopy each day following initial inoculation. We found that the hyphae of C. militaris invaded crevices and openings (spiracles) of the larvae and then spread throughout the body, but we did not observe a preference for particular tissues within the larvae.