Predatory behavior of three species of sac spiders attacking citrus leafminer

The predatory habit of three species of sac spiders, Chiracanthium inclusum , Hibana velox. and Trachelas volutus, on citrus leafminer, Phyllocnistis c itrella, was investigated. Observation of spider activities during the phot ophase and the scotophase confirmed that these three species of sac spiders are nocturnal. They detect their prey by sensing vibrations of the substra te induced by the concealed prey. Movements of P. citrella larvae and prepu pae appear to create vibrations of the leaf substrate, which then serve as cues for the spiders to locate them. The searching and prey capture behavio rs of these spiders are discussed. Two methods of prey attack were exhibite d. 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 pat tern, the spider makes a slit in the mine, uses its forelegs to pull the la rva or prepupa out of the mine, holds the prey securely, and finally bites it and regurgitates digestive juices into the prey and ingests the prediges ted 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 develope d to later instars. Maximum consumption for all species was recorded at the 4th instar. Although C. inclusum and T. volutus can complete their life cy cle with P. citrella as their only food, H. velox was not able to develop t o 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. c itrella.