Predation behaviors of Franklinothrips orizabensis (Thysanoptera: Aeolothripidae) towards Scirtothrips perseae and Heliothrips haemorrhoidalis (Thysanoptera: Thripidae)

The foraging behaviors of predatory female Franklinothrips orizabensis Johansen towards Scirtothrips perseae Nakahara and Heliothrips haemorrhoidalis (Bouch e) in avocado leaf arenas were videotaped and analyzed. F. orizabensis encountered and attacked more second instar S. perseae with 80% ðn 1⁄4 113Þ attacks on this life stage being observed compared to 20% on first instars ðn 1⁄4 28Þ when equal numbers of these prey were presented simultaneously. However, there was no significance difference by life stage for the probability of being attacked after being encountered. Successful attacks by F. orizabensis only occurred against propupal H. haemorrhoidalis ðn 1⁄4 6Þ that lacked protective fecal droplets, 65% of prey encounters were with this life stage, and 6% of encounters with propupae resulted in attacks. Second instar H. haemorrhoidalis larvae bearing protective droplets were encountered less frequently and were not attacked when contacted even though equal numbers of both stages were presented simultaneously. Consequently, the mean proportion of the time spent grooming by F. orizanbensis females attacking immatureH. haemorrhoidalis was four times greater than that for females attacking S. perseae larvae even though there was no significant difference in mean time (s) spent in each grooming bout. Significant differences in mean consumption times by F. orizabensis existed across life stages and prey species. Consumption times were shortest for first instar S. perseae larvae, intermediate for second instars, and longest forH. haemorrhoidalis propupae. Mean consumption times for sequentially attacked second instar S. perseae declined significantly indicating satiation of predators. Predators would spend on average approximately 7–13 s probing leaves with mouthparts and feeding on fluids; a behavior that on average occupied 2–5% of their time. This result may explain observed mortality of F. orizabensis in the laboratory and field when this predator forages on avocado leaves that have been treated with insecticides that exhibit translaminar activity. 2003 Elsevier Science (USA). All rights reserved.