Foraging generalist predators are frequently confronted with a diversity of prey types that differ in profitability. Optimal foraging models predict that predators should select and exploit the most profitable prey types and reject unprofitable ones. The goal of this research was to evaluate the mechanisms underlying prey selection, prey exploitation and predation efficacy in the generalist predator Coleomegilla maculata lengi Timb. (Col., Coccinellidae). / The influence of prey species, prey size and predator age on predation efficacy and prey consumption by C. maculata was determined using non-choice laboratory tests. The three lepidopterous species occurring in cruciferous crops, namely, Artogeia rapae (L.), Plutella xylostella (L.) and Trichoplusia ni (Hubner), were used as prey. Results showed that, within a given prey instar, C. maculata preyed more on P. xylostella than on the other two species and that predation efficacy increased with increasing predator age. These experiments also revealed that coccinellid larvae had a higher prey weight consumption rate on intermediate-sized prey compared to smaller or larger prey even though they killed a higher number of small prey. It is suggested that this higher efficacy on prey of intermediate size could be a consequence of higher costs associated with the consumption of prey at both ends of the size spectrum. / To evaluate behavioral parameters of prey selection in C. maculata larvae, an image analysis system, initially developed for parasitoids searching for hosts, was modified. This system was programmed to locate the eggs used as prey and to detect and follow the movements of the C. maculata larval head. This user-friendly system can detect and follow the movements with less than 0.1% of error. / Using this tracking system, the discriminatory capacity and the prey selection behavior of C. maculata larvae were evaluated in choice situations in which prey differed in quality (unparasitized, parasitized, young or old T. ni eggs). Coccinellid larvae did not exhibit any preference between parasitized and unparasitized eggs of the same physiological age. However, when physiological age differed, coccinellid larvae always preferred the younger eggs despite parasitism. Longer handling time and detrimental effects on immature developmental time and survival was always observed on the less preferred egg type. / This study also revealed that coccinellid larvae can learn to gradually reject the less suitable parasitized eggs, thereby improving their prey selection behavior. It was also demonstrated that these learned behaviors could be forgotten and that previous experiences on other prey types could influence the initial preference of coccinellid larvae. This study clearly indicates that the generalist predator C. maculata can select and exploit prey according to their profitability by using discrimination and learning abilities.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35935 |
| Date | January 1999 |
| Creators | Roger, Caroline. |
| Contributors | Boivin, Guy (advisor), Coderne, Daniel (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Natural Resource Sciences.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001657201, proquestno: NQ50249, Theses scanned by UMI/ProQuest. |
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