The predatory habit of three species of sac spiders, Chiracanthium inclusum, Hibana velox, and Trachelas volutus, on citrus leafminer, Phyllocnistis citrella, was investigated. Observation of spider activities during the photophase and the scotophase confirmed that these three species of sac spiders are nocturnal. They detect their prey by sensing vibrations of the substrate induced by the concealed prey. Movements of P. citrella larvae and prepupae appear to create vibrations of the leaf substrate, which then serve as cues for the spiders to locate them. The searching and prey capture behaviors of these spiders are discussed. Two methods of prey attack were exhibited. In one method, the spider punctures the mine, immobilizes the larva and then bites it and sucks the larval body fluid. In the second behavioral pattern, the spider makes a slit in the mine, uses its forelegs to pull the larva or prepupa out of the mine, holds the prey securely, and finally bites it and regurgitates digestive juices into the prey and ingests the pre-digested liquid tissue.
The three species of sac spiders were found to start feeding on P. citrella larvae during the 2nd instar stage. Consumption increased as they developed to later instars. Maximum consumption for all species was recorded at the 4th instar. Although C. inclusum and T. volutus can complete their life cycle with P. citrella as their only food, H. velox was not able to develop to the adult stage. Results obtained from this study provide useful data to better understand the role of sac spiders in the overall management of P. citrella.