A long slit-like entrance promotes ventilation in the mud nesting social wasp, Polybia spinifex: Visualization of nest microclimates using computational fluid dynamics
1Venture Business Laboratory, Graduate School of Science and Engineering, Ibaraki University, 316-8511, Japan
2Graduate School of Science and Engineering, Ibaraki University, 316-8511, Japan
Abstract
Polybia spinifex Richards (Hymenoptera: Vespidae) constructs mud nests characterized by a long slit-like entrance. The ventilation and thermal characteristics of the P. spinifex nest were investigated to determine whether the nest microclimate is automatically maintained due to the size of the entrance. In order to examine this hypothesis, a numerical simulation was employed to predict the effects of the entrance length. The calculations were performed with 3D-virtual models that simulated the P. spinifex nest conditions, and the reliability of the simulations was experimentally examined by using gypsum-model nests and a P. spinifex nest. The ventilation effect was determined by blowing air through the nest at 1-3 m/s (airflow conditions); the airspeed was found to be higher in models with a longer entrance. The ventilation rate was also higher in models with longer entrances, suggesting that the P. spinifex nest is automatically ventilated by natural winds. Next, the thermal effect was calculated under condition of direct sunlight. Under a calm condition (airflow, 0 m/s), thermal convection and a small temperature drop were observed in the case of models with a long entrance, whereas the ventilation and thermoregulation effects seemed small. Under airflow conditions, the temperature at the mid combs steeply dropped due to the convective airflow through the entrance at 1-2 m/s, and at 3 m/s, most of the heat was eliminated due to high thermal conductivity of the mud envelope, rather than convection.
Keywords: computational fluid dynamics, nest architecture
Abbreviations: CFD, computational fluid dynamics; GpM, gypsum model; VtM, virtual 3-D model
Correspondence:
ashoz@mx.ibaraki.ac.jp
Received: 16 February 2009 | Accepted: 31 May 2009 | Published: 11 October 2010
Copyright: This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, provided that the paper is properly attributed.
ISSN: 1536-2442 | Volume 10, Number 175
Hozumi S, Inagaki T. 2010. A long slit-like entrance promotes ventilation in the mud nesting social wasp, Polybia spinifex: Visualization of nest microclimates using computational fluid dynamics. Journal of Insect Science 10:175, available online: insectscience.org/10.175
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