Depending on the type of infestation, one might want specialists or generalists or both. Responses to herbivore-induced plant volatiles Plants produce volatiles when under herbivore attack. These odors are recognizable to predators as well as other herbivores. Herbivores can have two responses to these volatiles. They can take it to mean a food source with already weakened defenses, or a food source to avoid because of competition.
Spider mites have a slight preference for plants that are already infested with conspecifics.
The plant volatiles produced from thrip infestations are chemically different from the volatile produced from spider mite infestations. The reasons for avoidance of thrip infested plants is simple. When thrips aren t eating leaf tissue, they like to eat spider mites. This behavior avoids both competition and predation. This behavior has logical evolutionary pressure.