Diapause, and the environmental factors inducing hatching and breaking diapause

Some insects enter a period of diapause or aestivation during which development is delayed. These may be obligatory or facultative. Diapause enables insects to survive seasonally unfavourable conditions. With appropriate environmental control facilities it may be possible to artificially prevent diapause occurring or break diapause and thus increase the number of generations.

In the case of the univoltine Baccharis halimifolia chrysomelid, Trirhabda bacharidis, egg masses are covered in a cement that needs to be weathered off before diapause is broken. In the field this takes most of the year. In the insectary, the egg masses were watered regularly until eggs hatched (W.H. Haseler pers. comm. 1968). A similar technique has been used for breaking egg diapause in the Acacia nilotica chrysomelid Weiseana barkeri, whose egg masses are cemented together with maternal faeces (Marohasy 1994).

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