HABITS AND LIFE-HISTORIES OF WOODLICE. 149
in the larger species, and seldom more than three years in the
lesser species. In P. scaber and O. asellus three or four broods
are produced in a lifetime, the second year of breeding (i.e., when
three years old) being the year of greatest breeding activity, when
two successive broods may be produced in the same year ; then,
if they survive the following winter, a fourth brood is produced
in their fourth year of life.
In concluding this account I should like to express my
great indebtedness to Professor H. G. Jackson, D.Sc., of Birkbeck
College (University of London), whose expert guidance and help
have been a constant source of encouragement. My thanks are
also due to several members of the Club for helpful advice and
suggestions on the development of a satisfactory technique for
keeping the woodlice under constant observation and control,
which saved endless labour in the initial stages of the work.
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