Different Developments of Overwintered Larvae of Monochamus alternatus (Coleoptera, Cerambycidae) under a Constant Temperature

The overwintered larvae of Monochamus alternatus were collected from dead pine trees in mid-March and placed individually into fresh bolts of Pinus densiflora. Thereafter the larvae were incubated for 196 days under constant conditions of 25℃ and LD 16 : 8. The 4th (=final) instar larvae which had been in diapause emerged as adults 33-42 days after the beginning of incubation. The 4th instar larvae which had not been in diapause yet molted at least once, but did not emerge as adults during the incubation. The 1st to 3rd instar larvae developed into the diapausing 4th instar by the end of incubation. The overwintered 3rd and young 4th instar larvae skipped diapause during the final instar in our previous observations, whereas the chilled 3rd and young 4th instar larvae entered diapause in the present results. This discrepancy may have been caused by a constant temperature, fresh food, and/or adhesive cloth tape used in this experiment which prevented skipping diapause.