Influence of habitat and climate on the flight of male pine processionary moths

In the Aspromonte National Park (Calabria, Southern Italy), data were collected over 3 years on the flight of male pine processionary moths (PPM), as determined by pheromone traps, to determine the effect of habitat characteristics and climatic factors on male PPM flight. A variety of parameters, such as tree density, host tree species and the position of the traps, were investigated to analyze their effect on PPM catches in relation to weekly minimum temperatures and accumulated precipitation. The characteristics of the forest stands had a variable effect on moth catches. The abundance of PPM males caught was related to host Pinus species and to the size of patches, with a noticeable positive effect of temperature and a negative effect of precipitation. The host Pinus nigra, particularly when associated with other host species, such as Pinus sylvestris and Pinus insignis, smaller sized patches and lower density forests, positively affected moth flight. Flying males were caught above a threshold of a mean weekly temperature of 14 °C in combination with a photoperiod of >13.5 h of light with the flights in advance at higher altitudes. The relationship between the number of moths caught and nest density was evident in only 1 year, suggesting that the estimate of the population density based on the number of moths caught in the traps is possible only above a certain population density. A logistic model for all years is proposed to describe the relationships between the time scale and the cumulative percentage of flights.