The bright red beetles were a bonus. For several mid-July mornings my search amid the stalks of a common milkweed patch was focused on different shades of color, specifically the orange and black of monarch butterflies, and the white, black, and yellow striped pattern of their hungry caterpillars.
In our region the common milkweed is among the most important food sources for monarch caterpillars. When I found a cluster of more than twenty milkweed plants growing along the edge a gas pipeline right-of-way, I visited regularly to photo-document some aspects of this well-known plant and insect association for use in the museum’s expanding online educational resources. Although I eventually located and photographed several monarch caterpillar stages, my close encounters with red milkweed beetles resulted in many additional photographs and even the creation of a few 15-second bug action videos.
This long-horned beetle is known to the scientific world as Tetraopes tetraophthalmus, names derived from the Ancient Greek that each translate as “four eyes.” Anatomical studies of the species have concluded that what we see, even in the pictures illustrating this post, are in fact a single pair of eyes split in two by the creature’s antennae. The species is completely dependent upon milkweed. Female beetles lay their eggs on milkweed stems near the ground, and newly hatched larvae burrow into the ground to feed on the plant’s roots.
It’s easy to spot damaged leaves where the adults have been feeding, and if you inspect several such sections you might find evidence of a technique the beetle uses to minimize its exposure to the plant’s milky latex-like sap. The beetles are known to bite through a leave’s midrib before feeding to stop the flow of sap to their leafy buffet.
Patrick McShea works in the Education and Visitor Experience department of Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.