Host Plant Biochemical Influence on the Foraging and Food Utilization of Poecilocerus pictus and Danaus chrysippus on Calotropis gigantea: A Behavioral Ecology Approach.

Poecilocerus pictus and Danaus chrysippus are two common herbivorous insects that share the same host plant, Calotropis gigantea, yet they exhibit distinct feeding preferences and food utilization patterns across leaf ages. D. chrysippus larvae performed better on young leaves, which contain higher water content and suitable nutrients; before feeding, they cut leaf surfaces and inflorescence bases to interrupt latex flow and access floral sugars. P. pictus thrived on mature leaves, which offer a more balanced nutrient composition and moisture level; nymphs made serial cuts on the lower leaf surface to block latex, while adults typically fed from leaf tips. Both species performed poorly on senescent leaves, which are tough, nutrient-poor, and show altered glycoside profiles. Amino acids such as asparagine, proline, glutamine, glutamic acid, valine, alanine, and phenylalanine were more abundant in young leaves, likely explaining the strong preference of D. chrysippus, whereas mature leaves had an amino acid profile better suited to P. pictus. Gas chromatography-mass spectrometry (GC-MS) analysis revealed distinct phytochemical compositions among young, mature, and senescent leaves, as well as inflorescences. These chemical differences, particularly in water, nitrogen, and key metabolites, strongly influence the feeding behavior and growth of both the hemimetabolous grasshopper and the holometabolous butterfly.