| Summary: | <i>Trichogramma</i> spp. is an important egg parasitoid wasp for biocontrol of agriculture and forestry insect pests. Trehalose serves as an energy source or stress protectant for insects. To study the potential role of trehalose in cold resistance on an egg parasitoid, cDNA for trehalose-6-phosphate synthase (TPS) and soluble trehalase (TRE) from <i>Trichogramma dendrolimi</i> were cloned and characterized. Gene expressions and enzyme activities of <i>TdTPS</i> and <i>TdTRE</i> were determined in larvae, prepupae, pupae, and adults at sustained low temperatures, 13 °C and 16 °C. <i>TdTPS</i> and <i>TdTRE</i> expressions had similar patterns with higher levels in prepupae at 13 °C and 16 °C. <i>TdTPS</i> enzyme activities increased with a decrease of temperature, and <i>TdTRE</i> activity in prepupae decreased sharply at these two low temperatures. In vitro reared <i>T. dendrolimi</i> could complete entire development above 13 °C, and the development period was prolonged without cold injury. Results indicated trehalose might regulate growth and the metabolic process of cold tolerance. Moreover, 13 °C is the cold tolerance threshold temperature and the prepupal stage is a critical developmental period for in vitro reared <i>T. dendrolimi</i>. These findings identify a low cost, prolonged development rearing method, and the cold tolerance for <i>T. dendrolimi</i>, which will facilitate improved mass rearing methods for biocontrol.
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