Comparative study of temperature-dependent life histories of three economically important Adelphocoris spp.

Subsequent to the widespread adoption of Bt transgenic cotton in China and an associated reduction in pesticide use, Adelphocoris spp. (Hemiptera: Miridae) are the key pests of this crop. Three species (Adelphocoris suturalis, Adelphocoris fasciaticollis and Adelphocoris lineolatus) are found in Chinese Bt cotton fields, each with a distinct geographic distribution and phenology. In the present study, the development and fecundity of the three species are compared in the laboratory at various temperatures in the range 10-35 degrees C. Although nymphal development and adult moulting occurs under all temperature regimes, egg eclosion is not observed at 10 degrees C. In general, egg and nymphal development periods decrease with increasing temperature up to 30 degrees C. The lower and upper development thresholds are, respectively, 5.6 and 40.1 degrees C for A. suturalis eggs; 5.0 and 38.4 degrees C for nymphs; 6.3 and 39.0 degrees C for A. fasciaticollis eggs, 3.0 and 41.9 degrees C for nymphs; 5.6 and 41.3 degrees C for A. lineolatus eggs; and 6.2 and 38.8 degrees C for nymphs. Thermal constants are 189.9 degree days (DD) (egg) and 308.8 DD (nymph) for A. suturalis, 188.8 DD (egg) and 366.7 DD (nymph) for A. fasciaticollis, and 231.7 DD (egg) and 291.6 DD (nymph) for A. lineolatus. Temperatures above 30 degrees C affect egg development of A. fasciaticollis and A. lineolatus adversely, but not that of A. suturalis. At the same time, nymphal survival of A. suturalis is reduced at 10 degrees C. Longevity of all species declines with increasing temperature, whereas extremes of temperature (i.e. 10 and 35 degrees C) interfere with oviposition. The estimated optimum range for oviposition is 23-25 degrees C, irrespective of species. In general, development and fecundity of the three Adelphocoris spp. is consistent with their respective distribution and seasonal dynamics. The present study provides insight into the distribution and phenology of Adelphocoris spp., and contributes to the modelling of their population dynamics.