In 2012, we created a pollinator garden and sanctuary to assist in conservation efforts for the monarch and other butterflies and pollinators. We have several milkweed plants in our garden. Recently, we noticed a 5th instar monarch larva with an unusual marking that resembled the letter ex on its abdomen. The ex marking is clearly visible in this image captured as the larva rested on a leaf of a milkweed plant. This is the first time we have observed a caterpillar with such a mark. Now whenever we spot a monarch caterpillar in our garden we check its abdomen to make sure it has no extraordinary mark.