Elater Ferrugineus Research Articles

Sex Pheromone of Elater ferrugineus L. (Coleoptera: Elateridae)

The rare European click beetle, Elater ferrugineus L., develops exclusively in old, hollow deciduous trees. As a result of massive habitat loss caused by modern forestry, it is threatened throughout its entire distribution range and regarded as an indicator species for undamaged natural forests. As E. ferrugineus lives cryptically and its populations are frequently overlooked, we investigated its sex pheromone to develop a reliable detection tool. Pheromone gland extracts of single female E. ferrugineus were examined by using gas chromatography-mass spectrometry (GC-MS). All samples contained 7-methyloctyl 5-methylhexanoate, 7-methyloctyl octanoate, 7-methyloctyl 7-methyloctanoate, and 7-methyloctyl (Z)-4-decenoate in a ratio of approximately 1:1:3:3. Structures of all four esters, which have not been reported as pheromone compounds before, were confirmed by synthesis. A blend of the components was tested in the field and proved to be attractive for E. ferrugineus males, which were found to swarm exclusively during the day. This blend provides a noninvasive and effective monitoring method for this cryptic species, promising future collection records of E. ferrugineus in regions where it exists below the limit of detection by conventional collecting methods.

Attraction of the larval predator Elater ferrugineus to the sex pheromone of its prey, Osmoderma eremita, and its implication for conservation biology.

Elater ferrugineus is a threatened click beetle inhabiting old hollow trees. Its larvae consume larvae of other saproxylic insects including the threatened scarab beetle Osmoderma eremita. Recently, (R)-(+)-gamma-decalactone was identified as a male-produced sex pheromone of O. eremita. Here we present evidence that E. ferrugineus adults use this odor as a kairomone for location of their prey. In field trapping experiments, significantly more trapping events of E. ferrugineus beetles were observed in Lindgren funnel traps baited with (R)-(+)-gamma-decalactone than in control traps (20 vs. 1, respectively). Analyses of headspace collections from E. ferrugineus beetles indicate that the predator itself does not produce the substance. Both sexes were attracted to the prey pheromone. suggesting that E. ferrugineus males use the odor as an indirect cue for location of mates or of the tree hollows, which make up their habitat. When compared to pitfall traps, the Lindgren system was significantly more effective in trapping E. ferragineus, and no difference could be established for O. eremita, showing the high potential to use odor-based systems to catch both species. We suggest that (R)-(+)-gamma-decalactone could be used as a master signal in monitoring programs for these vulnerable beetle species. which are both regarded as indicators of the associated insect fauna of the threatened habitat of old hollow trees.

Influence of stand size and quality of tree hollows on saproxylic beetles in Sweden

The habitat requirements of 11 beetle species associated with tree hollows were studied by correlating their occupancy with characteristics of the oaks and the number of hollow oaks in each stand. The species richness was higher in trunks with a large girth and in tree hollows with entrances situated high up on the trunks and not directed upwards. Several species occurred with higher frequencies in larger stands, which suggests that these species are sensitive to habitat fragmentation. In some cases at least, the present species richness may reflect higher densities of hollow trees in the past. It is therefore suggested that, in order to preserve the rare fauna in old oaks, the stand size must be increased at many sites. In this study two species, Elater ferrugineus and Tenebrio opacus, were absent from almost all stands with <10 hollow oaks, whereas the other species occurred at least to some extent also in smaller stands. Presence/absence data of E. ferrugineus, T. opacus and Osmoderma eremita may be used to evaluate to what extent the fauna in old trees is affected by habitat fragmentation today as well as in the past.