Abstract:  Tetraphleps galchanoides Ghauri is an important predator of the hemlock woolly adelgid (HWA), Adelges tsugae Annand, in China. Its biology, habitats and prey habit were studied through breeding observation in the laboratory and field investigation. It occurs 2 generations per year without generation overlapping in Tianshengqiao Forest Farm, Lanping County, Yunnan Province. The 1st generation occurs in late May to late October. Egg period lasts 13.8±1.6 d, nymph period lasts 97.6±7.4 d, and adult period lasts 55.2±4.7 d. The 2nd generation occurs in mid November to late April of next year. Egg period lasts 11.3±1.1 d, nymph period lasts 105.7±8.5 d, and adult period lasts 60.4±5.3 d. The nymphs have 5 instars. The 2nd-generation adults emerge from overwintered 5th instar nymphs under bark of hemlock branch or ground litter. The sex ratio of female to male is 8.5∶1. Adults fly slowly usually at the lower canopy, and their flight was affected by mating, oviposition, and feeding. The optimum habitat for T. galchanoides is at the elevation range from 2 851 to 2 980 m, with forest coverage of 0.61-0.70, and with hemlock density 13.3-15.5/100 m. Food choice test was conducted among HWA and other 3 adelgids, i.e., Aphrastasia pectinatae (Cholodkovsky), Pineus armandicola Zhang, and Adelges laricis Vall. The results showed that there was a significant difference in its preference between HWA and the other adelgids. HWA was the most preferred prey. T. galchanoides can be used as one of the major natural enemies for the biological control of HWA.

Key words: Tetraphleps galchanoides, Adelges tsugae, biology, predation, habitat, food selection, biological control