Observation was made on the ecology of two Monochamus; M. alternates and M. saltuarius, by rearing them on pine timbers.
1. Adults of M. saltuarius begin to emerge from the host timbers at the middle of April and this emergence continues to early May, whereas emergence of M. alternatus takes place from early June to July, later than the former by about one month.
2. During flight period adults of both species feed upon the buds, the shoots and the bark of pine twigs, although M. alternatus feeds more on the bark than M. saltuarius does.
3. After feeding for about 3 weeks, mature adults deposit eggs in slits that they cut with their mandibles in the inner bark of pine trees. Oviposition is continued for two months in the case of M. alternates and for one month in the case of M. saltuarius.
4. The adult of M. alternates deposits 59 to 184 eggs per female extending over two months, whereas M. saltuarius 44 to 122 eggs in one month, 21.7 ovalioles per female being recognized in both species.
5. Egg period is 5 to 10 days in both species.