Byers, J.A. 1984b. Nearest neighbor analysis and simulation of distribution patterns indicates an attack spacing mechanism in the bark beetle, Ips typographus (Coleoptera: Scolytidae). Environmental Entomology 13:1191-1200.

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Entrance holes of Ips typographus (larger) and Pityogenes chalcographus (smaller) in Norway spruce
Abstract-- The attack sites of the bark beetle, I. typographus, on Norway spruce logs (Picea abies) were observed to be more uniformly spaced than random using nearest neighbor analysis. A computer model which simulated various degrees of uniformity in spatial distribution was compared to the observed attack pattern. The model showed that a mechanism of spacing between attacks, in which beetles need to be greater than a minimum distance of about 2.5 cm away from the nearest neighbor before attacking, can explain the observed distributions in nature. In the model, the distribution of angular directions to the 4 nearest neighbors appeared random, regardless of the degree of uniformity in the spatial distribution. The model for the mechanism of spacing can be applied to other organisms that exhibit uniform distributions.
Chemical Ecology