The feeding behavior of Oncopeltus fasciatus (Dallas) was studied from the standpoint of its being divisible into four behavioral components: (1) Orientation to the dietary substrate was found to be an antennal function, but could occur from only very short distances. Attractants in the milkweed seed coat elicited an orientation response. (2) Initiation of feeding involved contact of the labium with the diet. Labial contact was followed by stylet penetration and release of salivary secretions. Contact chemoreceptors on the labium were stimulated by unidentified chemical factors occurring in the milkweed seed coat. (3) Maintenance of feeding was found to be primarily dependent on sensory input from chemoreceptors situated internal to the stylets. Sugars and amino acids, as well as unidentified stimulants in the seed coat, played a role in determining the duration of feeding. (4) Cessation of feeding occurred as the result of sensory adaptation to the feeding stimulants and, probably, depletion of the insect's supply of salivary secretion. The feeding behavior pattern was followed by a water drinking behavior, mediated by hygroreceptors of the antennae and possibly unidentified internal receptors. After sensory disadaptation and renewal of salivary secretions, the bug was again ready to go into the feeding behavior pattern.