Gallery construction and oviposition of the bark beetle Ips typographus (Coleoptera: Scolytidae) at different breeding densities

Abstract

Abstract. 1. The bole of a Norway spruce, Picea abies(L.) Karst., was cut in 25 cm sections and infested in the laboratory with 2 or 8 females/dm2 of Ips typographus (L.) and an equal number of males.2. One log of each beetle density was dissected every second day, beginning 2 days after female introduction.3. The oviposition rate was highest at the beginning of the breeding period for both densities and then declined, especially at the high density. Residence time is a useful approximation for the number of laid eggs in the beginning of the oviposition period or when the density is low.4. Final gallery length and egg number per gallery were on average significantly smaller at density 8 than at density 2.5. Linear relationships between total gallery length and number of egg niches were found to be similar for the two densities.6. An estimate of the egg to adult mortality at different densities was found by using data from a field study that related gallery length to breeding density in attacked living trees, together with published relationships between density and egg niches or emergence of new adults.7. It was concluded that both decreased oviposition rate and earlier re‐emergence at higher densities contribute to a declining oviposition with increasing density. The final offspring production is futher reduced by lower survival due to larval competition as density increases.