Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department


Committee Member

Dr. Juang-Horng Chong, Committee Co-Chair

Committee Member

Dr. Peter H. Adler, Committee Co-Chair

Committee Member

Dr. David W. Tonkyn


Functional response describes the relationship between the number of prey consumed by a predator and the prey density. Three types of functional responses have been described based on the changes in prey consumption rates with increasing prey density. Plant architecture is one of several factors that can affect the searching efficiency, and thus functional response, of predators. The objective of this study was to investigate how the numbers of branches and leaves affected functional response of Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) when provided with Planococcus citri (Risso) (Hemiptera: Pseudococcidae) as prey. Greenhouse-grown chili peppers (Capsicum annum L., cv.'Jalapeño') were manipulated to achieve desirable numbers of primary branches (2, 4 and 6) (the "branch experiment") and numbers of leaves (5, 10 and 15) (the "leaf experiment"). The total surface areas were maintained constant in the two experiments to ensure that the detected differences in the functional response of C. montrouzieri were the results of varying branch or leaf number, not that of varying surface area. Results of this study suggested that C. montrouzieri exhibited Type II functional response on plants with 2, 4 and 6 branches, as well as on plants with 5 and 10 leaves. The lady beetle exhibited Type III functional response on plants with 15 leaves. Attack rates and handling time were not significantly different among treatments but slightly lower on plants with more leaves and branches, except the 15-leaved treatment had higher handling time than the 10-leaved treatment. Higher attack rates on plants with fewer branches and leaves suggested that C. montrouzieri was more efficient on plants of lower structural complexity. Higher handling time indicated that C. montrouzieri spent more time searching and consuming prey. The results of the study allowed pest managers to make better predictions on potential efficiency of C. montrouzieri and population dynamics in this prey-predator system.



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