Abstract: The nourishment of different parts of cotton plant, namely, the terminal leaf, bract, calyx, petal, anther, ovary, boll husk and boll heart, to cotton bollworm Helicoverpa armigera (Hubner) larvae and the distribution of terpenoid and tannin contents, the major secondary metabolites unfavorable to the larvae, in these cotton tissues were tested for exploring the relationship between feeding behavior of cotton bollworm larvae and the two kinds of allelochemicals in cotton. The results showed that the factthat the larvae preferred to feed on plant tip and bore into square and boll was closely related to the nutritive effect, mainly depended on the contents of terpenoids and tannins, of these organs on themselves. The tannin contents in terminal leaf gradually increased with the course of cotton's development, while there were significant drops ofterpenoid contents in terminal leaf in the 4th leaf, 6th leaf and early square stages, which were just the times the larvae damaged on cotton plant tip. The contents of secondary metabolites in outside parts of square and boll, such as bract, calyx, petal and boll husk, were higher than those in their inner parts, pollen, ovary and boll heart,etc. , and that in terminal leaf was intermediate. The terpenoids mainly presented in pigment glands, and tannins mainly scattered in the tissues of outer layer of cottonplants. It was indicated that certain feeding behavior of insect such as the feeding times and locations of cotton bollworm larvae is formed by its adaptability to the fluctuating contents of harmful secondary metabolites in host plant.

Key words: cotton bollworm, feeding behavior, cotton, allelochemical