Temperature, particularly extreme cold, is a key stressor that limits the distribution and abundance of insects. In response, various cold adaptations have evolved among insects, such as the accumulations of proteins and lipids, as well as low-molecular- weight cryoprotectants. Thitarodes pui is important as the host of Ophiocordyceps sinensis (Berk.) (G.H. Sung, J.M. Sung, Hywel-Jones and Spatafora) and has a limited distribution on Segrila Mountain in Nyingchi of the Tibetan Plateau. Low temperature is the main environmental stressor for T. pui, and although it is able to survive extreme cold, the mechanism is unclear. To determine the mechanism of cold adaptation, the composition of larvae hemolymph and soil temperature was investigated over 1 year (from April 2008 to March 2009) in T. pui habitats. Soil temperature exhibited a single curve, which peaked in August 2008 (11.31℃) and reached the lowest temperature in February 2009 (-0.05℃). The temperature of soil gradually increased from February to August and then decreased until the following February. To determine the factors involved in adaptation to low temperatures, the major components of hemolymph in T. pui larvae were isolated and classified as protein, total sugar, fat or glycerol. The correlation analysis between the components in hemolymph and soil temperature demonstrated that protein, total sugar and fat content fluctuated in response to the change in temperature during the study period. Among these components, proteins were most abundant in hemolymph and were present at the lowest level in September (8.37 mg/mL) and the highest in January (74.2 mg/mL). In spite of the slight decrease in November (32.41 mg/mL) and slight increase in June (34.44 mg/mL), protein levels gradually increased from September to January and decreased between February and August. There was a highly significant negative correlation with soil temperature, described by the function y=59.238-3.686x (r=-0.789, P=0.002). The second major component was total sugars (12.65-36.12 mg/mL), which remained at low levels during the summer and increased during the winter. There was a significant decrease between April and August, during which the soil temperature increased. The soil temperature remained low from December to February and the total sugar remained high. The relationship between total sugars and soil temperature was y=30.437-1.12x (r=-0.760, P=0.004), showing the same correlation as that between soil temperature and proteins. The fat content ranged from 7.7 to 12.46 mg/mL and correlated with soil temperature in the same manner as did the other components in larvae hemolymph, with y=11.413-0.307x (r=-0.924, P=0.000). Thus, the gross caloric value of hemolymph was lower in summer and higher in winter. The significant negative correlation between the gross caloric value and soil temperature is illustrated by the function, y=482.180-22.850x (r=-0.860, P=0.000). It is thought that glycerol is an important cryoprotectant in many insects that can respond quickly to fluctuations in the ambient temperature. Therefore, the present finding that glycerol levels were lower in larvae hemolymph of T. pui and that there was no significant correlation with soil temperature was surprising. This is in contrast with studies of other insects exposed to low temperature. These results show that it is important to enhance the cold hardiness of T. pui larvae to permit the accumulation of proteins, total sugar, and fat in hemolymph. However, the role of glycerol in cold resistance requires further study.