Emergence at lower temperatures facilitates movement of the flesh flies Parasarcophaga similis and Boettcherisca peregrina (Diptera: Sarcophagidae) into temperate and subarctic regions

: Differences in rates of diapause induction are thought to produce differences in the distribution of flies. Therefore, we investigated differences in the day length for entering diapause and effective chill treatment for termination of pupal diapause in Parasarcophaga similis and Boettcherisca peregrina flies found in Japan. Results showed maximum rates of diapause incidence for P. similis colonies from Sapporo, Tokyo and Nagasaki were 98% under 13L : 11D at 20°C, 100% under 11L : 13D and 80% under 10L : 14D, respectively. Diapause incidences for B. peregrina colonies from Tokyo and Nagasaki were 100% and 98% under 13L : 11D at 20°C. Emergence rates for diapausing pupae of P. similis (Sapporo) chilled at 4°C then transferred to diapause-terminating conditions at 27°C (16L : 8D) or 20°C (11L : 13D) were 65% and 80%. In B. peregrina (Tokyo), chill treatment was effective for 89% emergence. Adult P. similis (Sapporo) flies emerging from pupae that experienced chill treatment laid larvae that entered diapause at an incidence of 99.5%, whereas adult B. peregrina (Tokyo) laid 22% larvae destined for diapause. These flesh flies appear to move into new environments by successfully developing the ability to emerge at lower temperatures and possibly avoiding the maternal effect.