As strange as this is, it's utterly fascinating. The may beetle in this image expired soon after capture, so I pinned it as usual and then stored it in my collection, which I fumigated. Several months later, as I was scanning over several specimens, I noticed that this beetle had an extra protrusion at the end of its abdomen. Closer examination revealed that the object is the head of a Tachinid! Apparently, the fly managed to complete its development within the safety of the Scarab chassis, but failed to emerge from the rigid husk, dying with only its head exposed. This discovery was made around Oct. 2008.
The tachinid is a species of Cryptomeigenia, which specialize in parasitizing may beetles. ID by S.A. Marshall.