We used the slender forest skink (Scincella modesta) as a model animal to test for the hypothesis that the upper threshold of incubation
temperature is relatively low in lizards using shaded (and thus, cool) habitats. Eight gravid females were collected in early May 2005 from
a population in Hangzhou, Zhejiang (eastern China). All females laid a single clutch of 7–13 eggs between mid-May and early June. Eggs
were incubated at 24, 28 and 30 (70.2) 1C. None of eggs incubated at 30 1C hatched. Eggs incubated at 24 and 28 1C differed in
incubation length but not in hatching success. The incubation length at 24 and 28 1C averaged 22.3 and 20.3 days, respectively.
Hatchlings from eggs incubated at 24 and 28 1C did not differ in all examined morphological traits, but hatchlings from eggs incubated at
28 1C performed apparently worse in the racetrack than did their counterparts from eggs incubated at 24 1C. The temperature of 28 1C is
close to the upper thermal threshold for successful embryonic development in S. modesta. Compared to other oviparous lizards using
open (and thus, warm) habitats, the upper thermal threshold and the range of optimal temperatures for embryonic development are both
lower in S. modesta. Our study supports the previous conclusion that species living in thermally different habitats may differ in the upper
thermal threshold and the range of optimal temperatures for embryonic development