Infected beetles were collected and homogenized in sterile water. The homogenates were filtered through four layers of cheesecloth and centrifuged at 3000g for 15 min. The pellets were resuspended in sterile water, and the spores were purified by Percoll gradient centrifugation using 90% Percoll at 15,000g for 40 min. The spore band was collected and washed several times with sterile water. The purified spores (n = 50) were measured under a light microscope (IL/Leica Microsystems, Inc., Deerfield) with an ocular micrometer and photographed with the Microscope USB Camera.