Mark Bower sent me this picture of beetles covering his goldenrods. He tentatively identified them as Goldenrod Soldier Beetles.
I immediately recognized them as Pennsylvania Leatherwings. Looking them up I found that both names are commonly used to describe Chauliognathus pensylvanicus. I will leave that pronunciation to you.
Of even greater interest, there is a fungus association, a beetle made for our mycologist friend! To quote this Wikipedia entry:
"Adult C. pensylvanicus may be infected by the fungus Eryniopsis lampyridarum. After the fungus infects the host, it takes about two weeks for it to eventually kill its host. Before the host dies, the fungus orders the beetle to climb a plant and then attach itself to a flower by biting down with its mandibles into flower heads. About 15–22 hours later, the fungus causes the dead beetles to raise their elytra and expand their metathoracic wings in order to maximise infection of other beetles. With their wings raised, the dead beetles may still attract mates as live males were observed mating with the deceased, infected females, this then transmits spores from one insect-host to another."
| Journal of Invertebrate Pathology at this link |
This is a sexually transmitted disease (STD) or in this case an infection or STI. There is more recent information on this in this Science Alert story. The Parasite of the Day blog has more on the fungus association. As other soldier beetles are attracted to daisies, the plant acts as a pub which attracts other uninfected beetles. Sound familiar? Meanwhile other infected beetles fall to the ground where the fungi can survive until they hitch a ride on other beetles.
This is written in the name of science, even if it sounds a little X-rated.