The mortality rates of eggs, larvae, pupae, and adults of western flower thrips were investigated in our tests to give comprehensive evaluation of PH3 fumigation on insect control. Adults of western flower thrips were susceptible to PH3 fumigation similarly to greenhouse thrips (Heliothrips haemorrhoidalis) (Karunaratne et al., 1997), and eggs and pupae were verified to be more tolerant life stages, with 3-d-old eggs the most tolerant. The respiration rates of eggs and pupae were much lower than other life stages, and 3- d-old eggs might be much more mature than earlier eggs and were protected against PH3 toxicity by its corneum. Less tolerance of adults and larvae might be caused by the higher respiration rates and more absorption of PH3. PH3 treatment delayed hatching of eggs as eggs needed some time to recover from fumigation injury (Rajendran, 2000). This was consistent with research of Zhang et al.