Moisture-dependent insects (silverfish species and psocid species (Psocoptera)) in modern buildings – a sign of hidden moisture and mould damages

Abstract

Through the last 10 years, it has been an increasing occurrence and activity of moisture-dependent insects in modern buildings. Grey silverfish (Ctenolepisma longicaudata) is the most common species, but it is also an increasing number of cases of silverfish (Lepisma saccharina) and Ctenolepisma calva (Mattsson 2018). Furthermore, several psocid species (Psocoptera), which is well-known for living in microclimatically humid constructions (>60% RH) feeding on mould fungi, is commonly found in modern buildings in frequency and number that is traditionally not found in older buildings (>30 years). The populations of these insects also survive for several years in the modern buildings. This shows that there are persistent humid areas in constructions where they have suitable hotspots and access to suitable food. The humidity is due to residual building moisture and the moisture levels in such places are so high that there is a basis for growth for several species, such as Aspergillus penicilloides and A. versicolor. It is known that both mould spores and insect excrements can be allergenic. Our results show that there is a clear pattern in the abnormal occurrence of mold in dust and air in buildings where there are plenty of moisturedemanding insects. Thus, does the occurrence of these insects represent a clear risk for a negative indoor climate exposure.