Habrobracon hebetor (Say) from an eye color-mutant strain was used to determine the parasitoid’s cold hardiness. Supercooling points (SCP) for all stages of development were measured by surface contact thermometry and recorded as the lowest temperature reached before crystallization. Percentage mortality for pupae and adults at low temperatures was determined using minimum exposure (1 min) at temperatures ranging from -30ºC to 0ºC. Chill tolerance was assessed by placing adults at subzero temperatures above their mean SCP (e.g., -12ºC, -5ºC) for different intervals of time (h). Non-feeding stages (eggs and pupae) presented a lower mean SCP than feeding stages (larvae and adults). There were no significant differences in mean SCP between naked pupae and silk-encased pupae or between females and males. Food content in the guts reduced the supercooling capacity of adults about 8ºC. Percent mortality for pupae and adults when exposed for 1 min to subzero temperatures significantly increased (>50%) when their mean SCP was surpassed, indicating that H. hebetor is a freeze-intolerant insect. Habrobracon hebetor exposed to -5ºC for different time intervals showed 100% survival after 72 h; however, mortality reached 100% after 264 h, indicating that this insect is a chill susceptible organism. A better understanding of how well this parasitoid tolerates low temperatures may help us to determine its possible role as a biological control agent of stored-product moths in temperate regions.
Species 1: Hymenoptera Braconidae Habrobracon hebetor
Keywords: cold hardiness
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