Use of novel attraction compounds increases monitoring success of a rare beetle, Elater ferrugineus

Abstract

The use of pheromones to determine distributions of rare saproxylic insects is an increasingly popular technique. Pheromones may, however, also be used to elucidate the biology of these cryptic species, a vital requirement if they are to be accurately monitored and conserved. We used non‐invasive aerial trapping to compare the effectiveness of chemicals produced by Elater ferrugineus L (Coleoptera: Elateridae), namely 7‐methyloctyl (Z)‐4‐decenoate (the female‐produced sex pheromone), and male compounds (geranyl and neryl acetone and 6‐methyl‐5‐heptene‐2‐one). The male compounds were identified using headspace analysis by solid phase micro‐extraction gas chromatography‐mass spectrometry. We discovered that males only produce these two compounds after having been attracted to a female, and that this serves to attract further males to a female. Such compounds do not appear to attract females but for a species that has a short activity period and is non‐feeding in the adult stage, may ensure breeding success when populations are low. By marking all beetles caught, we were able to demonstrate that recapture rate using this method is low (approximately 11% of total captures annually). Therefore, the method does not limit dispersal or breeding opportunities, making it a valuable tool for monitoring endangered saproxylic beetle species.

Environmentally vulnerable noble chafers exhibit unusual pheromone-mediated behaviour

“…By comparison, they have been less utilized for insects of conservation status, only emerging over the last 15 years as a new approach that applies research outputs to the conservation of insect biodiversity [ 23 ], including mitigating the impact of human intervention and climate change. Pheromones have been isolated and used successfully as a monitoring tool for Osmoderma eremita Scopoli (Coleoptera: Scarabaeidae) [ 15 ], Elater ferrugineus L. (Coleoptera: Elateridae) [ 12 , 17 ], Rosalia alpina L. (Coleoptera: Cerambycidae) [ 18 ] and Graellsia isabellae Graëlls (Leptidoptera: Saturniidae) [ 24 ], enabling European countries to detect and, in some cases, map the range of some of these species, thereby proving a valuable technique for monitoring elusive saproxylic beetles [ 13 , 15 ]. Since several members of the Scarabaeidae use volatile pheromones for sexual communication [ 25 ], and due to the urgent need for a non-destructive detection tool for the conservation of the noble chafer, G .…”

“…Chemical ecological tools such as pheromones can be used as a recording technique for scarab beetles, enabling European countries to detect and, in some cases, map the range of some of these species, thereby proving a valuable technique for monitoring elusive saproxylic beetles [ 12 – 18 ]. Since many species in the Scarabaeidae use pheromones for sexual communication, and as there is an urgent need for a non-destructive detection tool for the conservation of G .…”

Making the invisible visible: determining an accurate national distribution of Elater ferrugineus in the United Kingdom using pheromones

“…This included traps to cover the historic distribution of E. ferrugineus as suggested by Stephens (1830) as well as that suggested by the NBN data (NBN Gateway, 2016). Monitors were advised, where possible, to hang traps at a height of 2 m (as determined by pilot work by Harvey et al, 2017). Traps were monitored for 3 weeks, to coincide with the activity of the species, without requiring excessive effort on the part of volunteers taking part in the study.…”

“…Each trap contained a 0.2 ml PCR tube (Starlab l1402-8100) pierced horizontally through the body of the tube with a small needle and suspended from copper wire through the closed lid with 2 ll of 7-methyloctyl-(Z)-4-decenoate, synthesised by EH, placed in the upper holding container. Monitors were advised, where possible, to hang traps at a height of 2 m (as determined by pilot work by Harvey et al, 2017). Traps were checked daily, beetles removed and released 10 m from the site of capture.…”

“…Colloquially known as the rusty red click beetle, E. ferrugineus is, at 15-24 mm long, the largest click beetle present in the UK. It has a life cycle of around 6 years, with annual adult emergence and mating between July and August (Harvey et al, 2017). Believed to inhabit hollows in old deciduous trees of Quercus sp.…”