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

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. .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 reemergence 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.

Reproduction abilities of Ips typographus (L.) (Coleoptera: Curculionidae, Scolytinae) in the stands damaged by the wind in 2013 in the Kościeliska Valley (Tatra National Park)

“…(observed: 16.22 ± 6.95; expected 1: 16.24 ± 3.25) are close to those (expected 3: 17.29 ± 4.35) estimated using the equation from Beskidy Mts. (Grodzki et al 2014) and far lower than the values (expected 2: 27.97 ± 6.84) resulting from the equation proposed by Anderbrant (1990) (Fig. 5).…”

“…When applying the simple regression model describing the relationship between the gallery length and number of progeny (see Fig. 3), as well as the other models based on the length of the maternal gallery proposed by Anderbrant (1990) and Grodzki et al (2014), both observed and expected average values from Kościeliska Valley were lower than the average number calculated using those models (Fig. 5).…”

“…5. Number of progeny per female calculated using three different models: expected 1, based on the actual correlation; expected 2, based on the regression model proposed by Anderbrant (1990); expected 3, based on the regression model proposed by Grodzki et al (2014) The estimation of expected number of progeny based on the maternal gallery length and resulting regression equation is not exact (Wilcoxon paired test -observed vs. expected 1: N = 1,891, T = 820,015.0, Z = 3.134, p = 0.0017); however, both average values from the Tatra Mts. (observed: 16.22 ± 6.95; expected 1: 16.24 ± 3.25) are close to those (expected 3: 17.29 ± 4.35) estimated using the equation from Beskidy Mts.…”

“…However, the parameters describing the populations, such as the sex ratio, fecundity and mortality, vary in subsequent outbreak phases (Anderbrant 1990;Lobinger 1996;Wermelinger 2002). However, the data on the bark beetle reproduction features, collected during the initial (progressive) outbreak phase, are of great importance for the assessment of the bark beetle outbreak potential and resulting mortality of attacked trees.…”

Statistical evaluation of Ips typographus population density: a useful tool in protected areas and conservation-oriented forestry

“…Christiansen et al 1987;Lieutier 2004). Wind-fallen trees reveal little or no resistance to beetle attacks allowing successful colonisation of their stems at low densities and thereby avoiding strong intraspecific competition (Anderbrant 1990). Hence, windfalls may result in a surplus of the breeding material, which in turn may lead to population outbreaks and subsequent attacks on standing healthy trees (e.g.…”