Water Vapor and Oxygen Exchange of Praying Mantis (Tenodera aridifolia sinensis) Egg Cases

Abstract

Mantid egg cases must be capable of preventing desiccation of the developing eggs for 5-6 mo while allowing adequate respiratory gas exchange for timely hatching. This investigation examined water vapor, oxygen, and thermal exchange of Chinese mantis (Tenodera aridifolia sinensis) egg cases. Water vapor conductance was 0.277 mg · d⁻¹ · mmHg⁻¹. Results of experiments with altered vapor pressure gradients, moving air, and hypobaria were consistent with water vapor loss by simple gaseous diffusion. Experiments at 100% relative humidity showed a linear increase in the internal egg case temperature with development, peaking more than 0.3° C above ambient temperature before hatching. Egg case O₂ consumption increased with increasing hatchling mass. Oxygen consumption at 25° C increased linearly with incubation time and for a case producing 1 g of hatchlings peaked at 537.5 μL · h⁻¹. The Q10's for O₂ consumption between 15° and 25° C were typical of insects. Calculations using diffusive gas exchange equations indicate the high resistance to water vapor flux does not result in embryonic hypoxia.