Peering closely at the faces of butterflies and moths, there is a lot of variation in the two labial palps that surround the proboscis. In butterflies they often jut out dorsally with a distinct conical tip, while others can be so fuzzy that the entire structures become indiscernible. Labial palps not only give lepidopterans unique expressions that we love to anthropomorphize, but also serve in important sensory functions. On the tip, sensilla (hairs) mainly serve as chemoreceptors to taste and smell, among other things aiding in correctly diagnosing their host plant(s). Many studies have also demonstrated sensilla can detect minute carbon dioxide gradients for locating recently bloomed flowers as a nectar source. Finally, some patches of sensilla are mechanosensory for maintaining their resting position around the proboscis, acting as a protective sheath. Although the neural circuitry has been described in many different sensillar structures, it is difficult to attribute one type of structure with a predominant role in any given sensory behavior. This is because lepidopterans have sensory organs located in many areas of the body, including the antennae, labial palps, abdomen, genitalia, legs, and feet.
Photographed after disturbance [4]