On the MPF Bioblitz, Christine presented me with the challenge above. They appeared to be a beetle larvae, but which ones and what is with the black flags? After thumbing through the usual sources, I sent it to Bi-State Bugs. Helen Wilbers pointed me in the right direction with Tortoise Beetle larvae, famed for collecting their fecal material on their backs as a shield. She suggested Physonota unipunctata as a likely suspect.
|P. helianthi - Bugguide -Tom Murray CC|
|Sunflower Tortoise Beetle - Tom Murray|
|Mature beetle - Kerry Yurewicz|
Tortoise Beetle larvae have an interesting defense as described in Bugguide.
"The larvae carry their cast skins and fecal material attached to spines arising from the posterior end of their body, a structure called an "anal fork." The anal fork is movable, and is used to hold the debris over the back of the body, forming a "shield" which deters predation."
|View of head with black anal forks naked - REK|
|Fecal shield on an "anal fork"|
More on fecal shields on this blog.