Insect must be able to overcome defense in order to feed on plant. Assume insect has mated and now has to locate the acceptable plant which its young or itself are able to utilize for food without being poisoned. Color is highly important to the honeybee in searching for flowers. Attracted to two-tone flowers and prefer flower that are in a patch.
Odors emanate from plant and leave a trail to the plant.
Insect perceives and homes in on source of odor. We call a factor which causes an insect to eat a phagostimulant . For many insects if the phagostimulant is not present they will not eat even if the food is highly nutritous. Will starve to death first. Cabbage butterfly uses mustard oil as a host location factor and as a phagostimulant.