The “Wallacean shortfall”—lack of distributional information—is one of the main problems when trying to assess the threats to and planning conservation strategies for many invertebrate species. Based on published and unpublished records since 1840, as well as on our own field survey, we attempted to estimate if and to what extent the use of pheromone traps increased the detectability of a rare, saproxylic click beetle Elater ferrugineus. The significant increase in the number of records in 2011–2013 shows that the pheromone method made it much easier to detect the occurrence of the species. Advantages of the pheromone method are that it does not disturb the habitat, can be used by non-specialists, is less costly and less time-consuming, and thus providing a useful tool for conservation research (studying biology, ecology and genetics of local populations).
Elater ferrugineus is a saproxylic click beetle inhabiting old deciduous trees in Europe. It is threatened throughout its area of distribution due to habitat loss. No efficient monitoring method has been available for this species, but observed attraction of females to (R)-(+)-γ-decalactone, which is a male-produced sex pheromone of its prey, the scarab beetle Osmoderma eremita, has led to the development of an odour lure for monitoring. In addition, four esters have recently been identified from the pheromone-producing gland in female E. ferrugineus, and a blend of these esters is highly attractive to conspecific males in the field, revealing an alternative odour-based method for monitoring this species. However, no rigorous analysis has been performed to check whether all four esters show biological activity in male E. ferrugineus, and whether its own sex pheromone is a more potent lure than the prey kairomone for monitoring of E. ferrugineus. In this study, we reinvestigated the E. ferrugineus sex pheromone, using electrophysiological and behavioural analyses, and found that only one of the esters, 7-methyloctyl (Z)-4-decenoate, is active. In addition, trapping experiments revealed that 7-methyloctyl (Z)-4-decenoate is a much more efficient attractant for male E. ferrugineus than the prey pheromone is for conspecific females, or any sex of O. eremita. With a very efficient odour lure at hand, novel information about current distribution, local population sizes, and dispersal ranges in E. ferrugineus can now be obtained, which can aid in conservation efforts to protect this threatened insect and its habitat. © 2011 Springer Science+Business Media B.V.
Pheromone-based monitoring could be a very efficient method to assess the conservation status of rare and elusive insect species, but there are still few studies for which pheromone traps have been used to obtain information on presence, abundance, phenology and movements of such insects. We performed a mark-recapture study of two threatened saproxylic beetles, Osmoderma eremita (Scarabaeidae) and its predator Elater ferrugineus (Elateridae), in two beech forests of central Italy using pheromone baited window traps and unbaited pitfall traps. Two lures were used: (1) the male-produced sex pheromone of O. eremita (racemic γ-decalactone) to attract females of both species, and (2) the female-produced sex pheromone of E. ferrugineus (7-methyloctyl (Z)-4-decenoate), to attract conspecific males. In total, 13 O. eremita and 1,247 E. ferrugineus individuals were trapped. For E. ferrugineus, males were detected earlier than females, and 7-methyloctyl (Z)-4-decenoate was much more efficient lure compared to racemic γ-decalactone in detecting its presence. The population size at the two sites were estimated to 520 and 1,369 individuals, respectively. Our model suggests a sampling effort of ten traps checked for 3 days being sufficient to detect the presence of E. ferrugineus at a given site. The distribution of dispersal distances for the predator was best described by the negative exponential function with 1 % of the individuals dispersing farther than 1,600 m from their natal site. In contrast to studies on these beetles in Northern Europe, the activity pattern of the two beetle species was not influenced by variation in temperature during the season.