Effects of photoperiod and temperature on seasonal morph development and diapause egg oviposition in a bivoltine race (Daizo) of the silkmoth, Bombyxmori L.

A bivoltine race (Daizo) of the silkmoth, Bombyx mori, has two types of adu lts which are classified on the basis of the number of dark-brown and brown scales distributed along the outer lines of the anterior wings. Developmen t of these two types of adults is determined by photoperiod and temperature experienced during the embryonic and larval stages. The two types of adult s are thought to be seasonal (summer and autumn) morphs. All adults develop ed under short days at low temperature (15 degrees C and 23 degrees) were c lassified as summer morphs and oviposited only nondiapause eggs (ND-eggs), and those that developed under long days at high temperature (28 degrees C and 25 degrees C) were autumn morphs ovipositing only diapause eggs (D-eggs ), only ND-eggs or a mixture of D- and ND-eggs. Larval exposure to long day s at 25 degrees C shifted the wing pattern towards the autumn morphs and de creased the incidence of female adults ovipositing only D-eggs. Larval expo sure to long days elicits an opposite effect on D-egg oviposition to that o bserved when long days are received only during the embryonic stage. (C) 19 99 Elsevier Science Ltd. All rights reserved.