Relative effects of plant (Solenostemon
scutellarioides) size and variegation on the searching efficiency and life
history characteristics of Cryptolaemus montrouziere (Coleoptera:
Juliana Ferreira Garcia
Advisor: Robert J. O'Neil
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Attack rates, search strategy and search behavior were measured for third instar Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) attacking third instar citrus mealybug, Planococcus citri Risso (Homoptera: Pseudococcidae), on green and yellow-variegated Solenostemon scutellarioides (L.) Codd (= Coleus blumei L.) plants of different sizes. Selected life history characteristics of C. montrouzieri from third instar to adulthood fed different amounts of P. citri as prey were also examined. Treatments included plants of different leaf color (green and yellow-variegated), morphology (such as, height, leaf area and leaf number) and numbers of mealybugs per plant (1, 8 and 16 mealybugs per plant). Five experiments were conducted. In the first experiment, “small” (ca. 2-week old) green and yellow plants of similar plant height, leaf number, and leaf area were used. The second and third experiments, consisted of “large” green and “large” yellow plants, with leaf area of 8-10 times that of the plants used in experiment 1. The fourth experiment used green and yellow plants similar in plant height and leaf area, but differing in leaf number. The fifth experiment used plants of similar leaf numbers, but different plant heights and leaf area. Attack rates were measured for a 24h period and searching behaviors were observed for 4h. On average predators attacked between 1 to 4 mealybugs depending on the number of mealybugs and plant size. There was no effect of plant color on attack rates and searching behavior. Attack rates were positively related to prey density, whereas the area searched by predators was inversely related to prey density. Analyses suggested that leaf area was the plant characteristic that most affected attack rates. Behavioral observations indicated that most attacks occurred on the same or nearby leaf were predators were initially placed. Predators that did not attack prey spent more time stationary. Predators changed their behavior after encountering and feeding on prey, to an area-restricted search movement. Predators fed few prey had a decrease in body weight and survival. The implications for these studies suggests that C. montrouzieri experiencing low attack rates under low prey densities, which if common in field situations, might result in a decline of predators survival and reproduction.
BIOLOGY, ENTOMOLOGY (0353); AGRICULTURE, AGRONOMY (0285); BIOLOGY, ECOLOGY (0329)