Experimental Density Manipulations of the Predator Tenodera sinensis (Orthoptera: Mantidae) in an Old-Field Community. I. Mortality, Development and Dispersal of Juvenile Mantids

Abstract

(1) Field and laboratory experiments were carried out to examine the effects of density on early life-history characteristics of the mantid, Tenodera sinensis. (2) For three replicated field treatments of threefold differences in initial mantid density, relative mortality was not density-dependent. Mortality was >90% for all treatments. Most mortality occurred among first-instar nymphs. (3) Laboratory experiments indicated that nymphs could survive crowded conditions if provided with sufficient food. Cannibalism was negligible among well-fed nymphs at all densities. Starved nymphs exhibited substantial cannibalism, but this was not related to density. (4) Rate of development, measured as changes in proportion of nymphs among instars over time, was negatively related to density in the field. Laboratory tests indicated that this was probably due to food limitation. (5) Relative dispersal, measured by monitoring nymphs caught in Tangletrap barriers surrounding experimental field plots, increased with increasing density. This contributed to overall convergence in density to similar levels among treatments and may help to regulate natural populations of this species. Most dispersal occurred among second-instar nymphs.