Predatory checkered beetles occur in many historical buildings. Thus, it is essential to learn more about the ecology of these beetles, specifically for their further use as suitable beneficial organisms in biological control of wood-destroying insects. In this study, indoor climatic conditions were examined as a major factor influencing their occurrence and that of their prey Anobium punctatum and Xestobium rufovillosum. For this purpose, monitoring and climate measurements were implemented in nine historic buildings in North-Eastern Germany (Mecklenburg-Vorpommern). A collective occurrence of Opilo domesticus and Korynetes caeruleus together with the wood boring pests was shown via sticky traps and collections of adult beetles. The exit holes of O. domesticus and Opilo mollis in paper covers used to monitor hatching-activity are not sufficiently species-specific and are therefore not considered in the evaluation of the climate data. Usually only annual and monthly mean values for temperature and relative humidity have been considered to discuss the occurrence of the insects mentioned. Anobium punctatum and X. rufovillosum, as well as their predators K. caeruleus and O. domesticus, have been found in half-timbered and solid structures. According to this, their climatic requirements must be quite similar. As a new study approach, climatic conditions for the period of walking and flight activity (reproductive phase via sticky traps and collections) were studied separately for both, the beneficial insects and wood pests. The results obtained so far partially showed significant differences for the insect species investigated. Anobium punctatum reproduces within narrowly defined temperature intervals with an optimum between 15.5 - 18 °C. For the reproductive phase of O. domesticus, the optimal temperatures are between 16.5 - 18 °C, up to about 23 °C, which almost exactly corresponds to those of A. punctatum. However, there are differences in humidity requirements. The beetles of O. domesticus have only been recorded at a rel. humidity of 64 - 73 %. This range of rel. humidity is narrower than for A. punctatum, whose beetles are found in buildings with rel. humidity from 55 - 80 %. These differences in climatic requirements may be part of the reason for the less frequent occurrence of O. domesticus beetles in only three buildings and the greater distribution and abundance of A. punctatum in all nine buildings. The obtained results from these studies and those of previous findings regarding climatic conditions will help successful breeding of checkered beetles in the laboratory for biological control purposes.

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