Jonathan P. Lelito

Visually Mediated ‘Paratrooper Copulations’ in the Mating Behavior of Agrilus planipennis (Coleoptera: Buprestidae), a Highly Destructive Invasive Pest of North American Ash Trees

The emerald ash borer, Agrilus planipennis, is a serious invasive pest of North American ash (Fraxinus) trees. In captivity, mating is initiated by beetles at least 10xa0days old, and appears to be based simply on random contact with a member of the opposite sex. In the field, male A. planipennis search the tree during flight, and attempt to copulate with dead beetles of both sexes pinned to leaves, after descending rapidly straight down onto the pinned beetles from a height of from 30 to 100xa0cm. All evidence suggests that males find potential mates using visual cues. Equal numbers of feral males approach all ‘dummy’ beetles; however, considerably more time is spent attempting copulation with dead females rather than males, suggesting a contact chemical cue. Sticky traps prepared from dead, pinned EAB capture crawling insects as well as male A. planipennis, at a rate similar to that at which small purple sticky traps of similar overall area capture crawling insects and both sexes of feral EAB.

Novel visual-cue-based sticky traps for monitoring of emerald ash borers, Agrilus planipennis (Col., Buprestidae).

We examined various methods of trapping emerald ash borers (EAB), Agrilus planipennis Fairmaire, using solely visual cues based on previous work that has documented the importance of visual cues in EAB mate location. Here, we give the results of two of these methods, coloured sticky cards (yellow or blue), or live ash leaves covered with spray‐on adhesive to which dead male EAB visual lures had been pinned. Feral male beetles were captured effectively on the sticky traps made from dead male EAB on ash leaves. These sticky‐leaf‐traps captured more male EAB when deployed in high‐population density areas than low‐density areas, but did capture EAB even at lower population densities. More feral males were captured on these traps when they were placed higher in the trees, regardless of the population density of EAB. Very few feral female EAB were captured using the sticky‐leaf‐traps. This novel method of EAB trapping may allow ‘real‐time’ population detection and monitoring of EAB adults during the active flight period rather than locating larval galleries during the autumn and winter after adult flight and attack. Feral male beetles were also captured using standard yellow‐ or blue‐coloured sticky cards to which male EAB had been affixed with adhesive; however, this type of trap was much less effective overall than using the sticky‐leaf‐traps. Furthermore, Agrilus cyanescens, a species similar in colour to EAB but smaller in size, showed a strong response to blue‐coloured sticky traps to which dead male EAB had been affixed with adhesive, suggesting a general use of visual cues in the mating systems of some of the other Buprestidae as well.

Behavioral Evidence for a Contact Sex Pheromone Component of the Emerald Ash Borer, Agrilus Planipennis Fairmaire

The cuticular hydrocarbon profiles of emerald ash borers, Agrilus planipennis, were examined to determine if there are differences in these compounds between the sexes. We also assessed feral male EAB in the field for behavioral changes based on the application of a female-specific compound to dead, solvent-washed beetles. Males in the field spent significantly more time attempting copulation with dead, pinned female beetles coated with a three-beetle-equivalent dose of 3-methyltricosane than with solvent-washed beetles or those coated in 3-methyltricosane at lower concentrations. Males in the field spent the most time investigating pinned dead, unwashed female beetles. In the laboratory, sexually mature males were presented with one of several mixtures applied in hexane to filter paper disks or to the elytra of dead female beetles first washed in solvent. Male EAB also spent more time investigating dead beetles treated with solution applications that contained 3-methyltricosane than dead beetles and filter paper disks treated with male body wash or a straight-chain hydrocarbon not found on the cuticle of EAB.

Visual and chemical cues affecting the detection rate of the emerald ash borer in sticky traps

Using sticky traps, we compared the efficacy of chemical and visual lures, both alone and in combination, for improving the detection of populations of the emerald ash borer (EAB), Agrilus planipennis. Ash leaflets to which EAB visual decoys were pinned and coated with sticky material were able to trap EAB with as high a rate of detection as large sticky visually unbaited ‘prism traps’ currently used in wide‐scale EAB surveillance programs in North America, in a high‐density area. Both the sticky leaf traps and prism traps captured more EAB when a point source of plant odours, either manuka or phoebe oil, was deployed with the trap. For the sticky leaf traps, the shape of the EAB visual decoy lure was found to be important in optimizing the detection rate. Either an entire dead beetle or else two elytra placed side by side to mimic a resting beetle resulted in optimal trap performance. When two elytra were placed end to end or else other body parts were deployed, the traps lost their efficacy. Small green plastic surfaces to which EAB visual decoys were pinned were found to be fairly good substitutes for live ash leaflets, but the rate of beetle detection was reduced significantly from that of the ash leaflet plus EAB decoy. Throughout all experiments, a clear male bias occurred in sticky leaf traps when EAB visual decoys were placed on the traps. The implications of these findings for developing new trapping designs for EAB and other forest buprestids are discussed.

Detecting emerald ash borers (Agrilus planipennis) using branch traps baited with 3D-printed beetle decoys

Small visual-decoy-baited traps for the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), have been researched as an alternative to current technologies, but have relied on real beetles rather than synthetic materials. We hypothesized that visual decoys created by three-dimensional (3D) printing can provide such a substitute. Branch traps displaying decoys consisting of real EAB females or 3D-printed decoys were compared to controls without decoys. Traps of the three varieties were placed on neighboring branches along with one (Z)-3-hexen-1-ol lure per tree and checked daily. Both real and 3D-printed decoys similarly increased EAB trap captures compared to controls. The numbers of both sexes were higher on the decoy-baited traps, but the increase in male captures was more pronounced. Males were also ensnared closer to the decoys than females. Daily trap–capture patterns showed sparse activity of EAB adults before June 18, 2013 followed by a peak in captures of both males and females until June 28, 2013. Beginning at approximately July 1, 2013, there was a second peak of EAB captures, which consisted almost entirely of males caught on the decoy-baited traps. The native ash borer Agrilus subcinctus was found earlier in the season and was also significantly attracted to both the real EABs and the 3D-printed decoys compared with control traps. Four purple prism traps were also deployed concurrently and captures tallied on three different days within the season. The results demonstrate efficacy of a small, inexpensive, and fully synthetic decoy-based branch trap system for EAB.

Trapping of European buprestid beetles in oak forests using visual and olfactory cues

Trapping approaches developed for the emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), were adapted for trapping several European oak buprestid species. These approaches included the use of natural leaf surfaces as well as green and purple plastic in sticky trap designs. Plastic surfaces were incorporated into novel ‘branch‐trap’ designs that each presented two 5 × 9‐cm2 rectangular surfaces on a cardboard structure wrapped around the leaves of a branch. We used visual adult Agrilus decoys in an attempt to evoke male mating approaches toward the traps. Our first experiment compared the attractiveness of visual characteristics of the surfaces of branch‐traps. The second looked at the effect on trap captures of adding semiochemical lures, including manuka oil, (Z)‐3‐hexen‐1‐ol, and (Z)‐9‐tricosene. In total, 1 962 buprestid specimens including 14 species from the genus Agrilus were caught on 178 traps in a 22‐day time‐span. Overall, the green plastic‐covered branch‐traps significantly out‐performed the other trap designs. We further found that the presence of an EAB visual decoy placed on the trap surface often increased captures on these green traps, but this effect was stronger for certain Agrilus species than for others. The visual decoy was particularly important for the most serious pest detected, Agrilus biguttatus Fabricius, which was captured 13 times on traps with decoys, but only once without a decoy. There were some small but significant effects of odor treatment on the capture of buprestids of two common species, Agrilus angustulus Illiger and Agrilus sulcicollis Lacordaire. There were also 141 Elateridae specimens on these traps, which were not influenced by trap type or decoys. The results suggest that small branch‐traps of this nature can provide a useful new tool for monitoring of buprestids, which have the potential to be further optimized with respect to visual and olfactory cues.

Interspecific Pheromone Plume Interference Among Sympatric Heliothine Moths: A Wind Tunnel Test Using Live, Calling Females

Three species of North American heliothine moths were used to determine the level at which interspecific female interference of male attraction to conspecific females occurs. We used live calling females of Heliothis virescens, H. subflexa, and Helicoverpa zea, as lures for conspecific males in a wind tunnel, and then placed heterospecific females on either side of the original species such that the plumes of the three females overlapped downwind. In nearly all combinations, in the presence of heterospecific females, fewer males flew upwind and contacted or courted the source than when only conspecific females were used in the same spatial arrangement. Males did not initiate upwind flight to solely heterospecific female arrangements. Our results show that the naturally emitted pheromone plumes from heterospecific females of these three species can interfere with the ability of females to attract conspecific males when multiple females are in close proximity. However, the fact that some males still located their calling, conspecific females attests to the ability of these male moths to discriminate point source odors by processing the conflicting information from interleaved strands of attractive and antagonistic odor filaments on a split-second basis.

Field Investigation of Mating Behaviour of Agrilus cyanescens and Agrilus subcinctus

Abstract n We examined mate-finding behaviour in Agrilus subcinctus Gory (Coleoptera: Buprestidae) and Agrilus cyanescens Ratzeburg (Coleoptera: Buprestidae) in ash (Fraxinus L. (Oleaceae)) stands in the Great Lakes region of the United States of America. Dead specimens of both species were affixed to ash foliage to serve as models to test visual stimulation of aerial attraction of males. The models were washed in dichloromethane to remove cuticular lipids or were left unwashed, to test for the presence of close-range pheromonal cues. Males of both species located females via a visually guided aerial approach from up to 1 m above females, similar to the behaviour of Agrilus planipennis Fairmaire. When male A. subcinctus or A. cyanescens made contact with females, contact sex pheromones mediated subsequent copulation behaviour. During their visually mediated airborne descent and landing, male A. cyanescens landed directly on female models; whereas, male A. subcinctus landed significantly more often on the leaf surface supporting a model. Male A. subcintus performed precopulatory pounce behaviour on female models after assessing surface chemical cues with their antennae. Male A. cyanescens landed upon a variety of models, but after landing, rejected a significant proportion of models lacking female A. cyanescens cuticular lipids.

A cure for the blues: opsin duplication and subfunctionalization for short-wavelength sensitivity in jewel beetles (Coleoptera: Buprestidae).

BackgroundArthropods have received much attention as a model for studying opsin evolution in invertebrates. Yet, relatively few studies have investigated the diversity of opsin proteins that underlie spectral sensitivity of the visual pigments within the diverse beetles (Insecta: Coleoptera). Previous work has demonstrated that beetles appear to lack the short-wavelength-sensitive (SWS) opsin class that typically confers sensitivity to the “blue” region of the light spectrum. However, this is contrary to established physiological data in a number of Coleoptera. To explore potential adaptations at the molecular level that may compensate for the loss of the SWS opsin, we carried out an exploration of the opsin proteins within a group of beetles (Buprestidae) where short-wave sensitivity has been demonstrated. RNA-seq data were generated to identify opsin proteins from nine taxa comprising six buprestid species (including three male/female pairs) across four subfamilies. Structural analyses of recovered opsins were conducted and compared to opsin sequences in other insects across the main opsin classes—ultraviolet, short-wavelength, and long-wavelength.ResultsAll nine buprestids were found to express two opsin copies in each of the ultraviolet and long-wavelength classes, contrary to the single copies recovered in all other molecular studies of adult beetle opsin expression. No SWS opsin class was recovered. Furthermore, the male Agrilus planipennis (emerald ash borer—EAB) expressed a third LWS opsin at low levels that is presumed to be a larval copy. Subsequent homology and structural analyses identified multiple amino acid substitutions in the UVS and LWS copies that could confer short-wavelength sensitivity.ConclusionsThis work is the first to compare expressed opsin genes against known electrophysiological data that demonstrate multiple peak sensitivities in Coleoptera. We report the first instance of opsin duplication in adult beetles, which occurs in both the UVS and LWS opsin classes. Through structural comparisons of known insect opsins, we suggest that opsin duplication and amino acid variation within the chromophore binding pocket explains sensitivity in the short-wavelength portion of the visible light spectrum in these species. These findings are the first to reveal molecular complexity of the color vision system within beetles.

Latitudinal variation in body size of Agrilus planipennis and relationship with fecundity

For many animals with a wide geographical range, latitude is important in determining body size. Additionally, insect body size often has a direct influence on fecundity. Identifying these relationships for a forest pest can add to population dynamics modelling. Agrilus planipennis is a pest of North American Fraxinus species. The relationship between A. planipennis body size and latitude was investigated through field trapping adult A. planipennis in eastern U.S.A., and the relationship between body size and fecundity was investigated through egg production of laboratory‐reared A. planipennis adults. Accumulated growing degree days base 10u2009°C (GDD10) were calculated and used to identify the influence of local climate on A. planipennis body size. Adult female A. planipennis body size (length and mass) was negatively related to latitude, with larger individuals at southerly sites where the number of days to accumulate 450 and 1000 GDD10 was the lowest. Using positive linear models relating body size and eggs produced, females from southerly sites would potentially produce twice as many eggs as females from northerly sites. Agrilus planipennis population latitudes influenced female body size. Because larger A. planipennis females produced more eggs, there is a potential for populations at southerly sites to increase in density and geography more rapidly than northerly populations.