We investigated the heat shock response of the apple maggot, Rhagoletis pomonella, throughout its larval development in the apple as well as through its overwintering pupal diapause. During the feeding phase of larval life, the larvae can be exposed to temperatures above 40°C inside the apple. After feeding, the larvae drop to the soil and pupariate. Developmentally most pupae enter a long diapause (~ 11months), but some will enter a shallow diapause (up to 3months), while others directly develop into adults. We studied the expression patterns of the genes encoding heat shock proteins 70 and 90 during the feeding phase inside the apple, during pupal diapause, and in the adult stage. Larvae were reared at 28°C, 35°C or in the field. Diapausing pupae were sampled 30, 60, 90, 120, 150 and 180 days post-pupariation. Hsp70 was not upregulated in larvae reared at 28°C but was expressed in those reared at 35°C. In contrast, Hsp90 was strongly upregulated in larvae reared at 28°C, but expression declined at 35°C. In adults, both Hsps were strongly upregulated in response to a 38°C 1 hr heat shock. Hsp70 was strongly upregulated at the onset of diapause, expression declined at 60 and 90d, but was again strongly expressed at 120d. Hsp90 was constitutively expressed throughout diapause. We conclude that the apple maggot is well defended against heat shock by employing Hsp70 and 90 during larval development and developmentally turns in the expression of Hsp70 at the onset of diapause and again in deep diapause.