Abstract
The sex ratio of the polygamous species Ips acuminatus (Gyllenhal) varied in 31 localities of Norway from 1 to 4 females per male in northern and western areas to 20 females and more in some southeastern areas. The number of female galleries per nuptial chamber (usually three to five) varied accordingly and isolated female galleries were also formed. Laboratory breedings showed that the species has two types of females, one which produces only females and one which produces both-sixes usually with a 1:1 sex ratio.
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