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Near-Optimal Foraging in the Pacific Cicada Killer Sphecius convallis Patton (Hymenoptera: Crabronidae)
Institute for Franciscan Environmental Studies, Biology Program, Quincy University, Quincy, IL 62301, USA
Department of Biological Sciences, Northern Kentucky University, Highland Heights, KY 41099, USA
Department of Biology, Lafayette College, Easton, PA 18042, USA
* Author to whom correspondence should be addressed.
Received: 1 January 2012; in revised form: 21 January 2012 / Accepted: 1 February 2012 / Published: 10 February 2012
Abstract: This study evaluated foraging effectiveness of Pacific cicada killers (Sphecius convallis) by comparing observed prey loads to that predicted by an optimality model. Female S. convallis preyed exclusively on the cicada Tibicen parallelus, resulting in a mean loaded flight muscle ratio (FMR) of 0.187 (N = 46). This value lies just above the marginal level, and only seven wasps (15%) were below 0.179. The low standard error (0.002) suggests that S. convallis is the most ideal flying predator so far examined in this respect. Preying on a single species may have allowed stabilizing selection to adjust the morphology of females to a nearly ideal size. That the loaded FMR is slightly above the marginal level may provide a small safety factor for wasps that do not have optimal thorax temperatures or that have to contend with attempted prey theft. Operational FMR was directly related to wasp body mass. Smaller wasps were overloaded in spite of provisioning with smaller cicadas, while larger wasps were underloaded despite provisioning with larger cicadas. Small wasps may have abandoned larger cicadas because of difficulty with carriage.
Keywords: wasp; optimal foraging; cicada; desert; insect; load carriage; flight; force
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Coelho, J.R.; Hastings, J.M.; Holliday, C.W. Near-Optimal Foraging in the Pacific Cicada Killer Sphecius convallis Patton (Hymenoptera: Crabronidae). Insects 2012, 3, 133-140.
Coelho JR, Hastings JM, Holliday CW. Near-Optimal Foraging in the Pacific Cicada Killer Sphecius convallis Patton (Hymenoptera: Crabronidae). Insects. 2012; 3(1):133-140.
Coelho, Joseph R.; Hastings, Jon M.; Holliday, Charles W. 2012. "Near-Optimal Foraging in the Pacific Cicada Killer Sphecius convallis Patton (Hymenoptera: Crabronidae)." Insects 3, no. 1: 133-140.