Every year around this time as the Queen butterflies start to show up, we get lots of questions about how to tell the difference between Queens, Danaus gilippus, and Monarchs, Danaus plexippus. And with the warm weather that has gripped South Texas throughout November and now December, many of us are still finding eggs and caterpillars in the leaves of our milkweed. Queens are here en masse.
As it turned out, the caterpillar in question that my friend Hugh texted me about (excuse the typos) was in fact a Queen. The giveaway: it had three sets of protuberances, rather than two. These protuberances are often referred to as antennae, but they are actually a type of sensory organ called tentacles. Most caterpillars–including Monarchs–have a set of tentacles at the front of the body and another at the back, but others–like Queens–have another set somewhere in the middle. Tentacles help caterpillars sense the world around them through touch, and can also throw off predators by disguising the caterpillar’s head. Caterpillars also have antenna, but these organs are far less obvious and helpful for identification. The antennae are short, spiky projections on either side of the caterpillar’s mouth.