The association of Lepidoptera with small groups of related plants is a well developed paradigm. Plants differ in their chemical defenses and caterpillars differ in their ability to detoxify chemicals. Caterpillars have limited mobility and cannot travel long distances to find an acceptable food plant. The decision as to what the caterpillar eats rest with the mother who must select where to place her eggs.
Many species of Lepidoptera contain arrays of receptors on the ovipositor including chemoreceptors. A study* of the ovipositor of the armyworm, Spodoptera littoralis found multiple arrays of sensory receptors. One type of receptor is a classic taste receptor. Each receptor has multiple nerves that responding to either Sweet, Salt, Caffeine and Water. The taste receptors allow the female moth to “taste” the plant and evaluate is potential as food for offspring prior to laying eggs.
*Mervat A. SEADA, Rickard IGNELL and Peter ANDERSON Morphology and distribution of ovipositor sensilla of female cotton leaf worm Spodoptera littoralis (Lepidoptera: Noctuidae), and evidence for gustatory function. Entomological Science (2016) 19, 9–19.