A Symmetrical Diester as the Sex Attractant Pheromone of the North American Click Beetle Parallelostethus attenuatus (Say) (Coleoptera: Elateridae)

Discovery and Field Evaluation of Sex Pheromone Components for the Click Beetle Melanotus verberans (LeConte) (Coleoptera: Elateridae)

Wireworms, the larval stage of elaterid beetles, are among the most serious soil-borne insect pests in the world. Wireworms feed on a variety of key crops, including small grains, maize, vegetables, fruits, sugar cane, sugar beets, potatoes, and sweet potatoes. Management of these pests is becoming increasingly problematic, in part due to knowledge gaps in their basic biology, which hinders development of effective crop protection strategies. In particular, little is known about the semiochemicals that mediate the reproductive behavior of these pests. Research over the past two decades has begun to fill this need, with: (1) the discovery of sex attractants for several key pest species, and (2) subsequent studies toward development of semiochemically-based pest management approaches. We used chemical and behavioral studies to identify, synthesize, and field test the sex attractant pheromone of adult Melanotus verberans, the larvae of which are important crop pests. In coupled gas chromatography-mass spectrometry analyses of extracts of ovipositors of females, five possible pheromone components were identified. Subsequent coupled gas chromatography-electroantennogram detection analyses indicated that male antennae were responsive to only two of these compounds, 13-tetradecenyl acetate and 13-tetradecenyl hexanoate. In field trials, neither compound alone was attractive, but a blend of the two was strongly attractive to conspecific male beetles, and did not attract other species. A two-year field study showed that most male beetle flight activity occurred from April through May. Because the sex pheromone of M. verberans consists of two compounds that can be readily synthesized, its development for integrated pest management should be economically feasible.

Identification of sex attractants for 6 North American click beetle species in 4 tribes of the Elateridae

We describe experiments that evaluated potential sex pheromone components for 6 North American click beetle species. In field trials in Illinois, South Carolina, North Carolina, and Virginia, male beetles of 6 species were strongly attracted to geranyl butyrate (Agriotes insanus Candèze), 5-methylhexyl (Z)-4-decenoate (Elater abruptus Say), 11-dodecenyl butyrate (Melanotus ignobilis Melsheimer), and limoniic acid (Gambrinus griseus [Palisot de Beauvois], G. rudis [Brown], and G. plebejus [Say]). Collection of E. abruptus in South Carolina represents a new state record. For each species, capture rates varied geographically and temporally, possibly due to differences in local population densities and regional phenology, or the efficiency of different trap designs or trap placement. Structural similarities were observed between the tested attractants and previously identified pheromones of closely related species. For example, males of A. insanus were attracted to geranyl butyrate, analogous to the terpenoid ester pheromones of a number of European congeners. The attractant for E. abruptus, 5-methylhexyl (Z)-4-decenoate, is an analog of the pheromone of its European congener E. ferrugineus L., and the attractant for M. ignobilis, 11-dodecenyl butyrate, is an analog of attractants of European and Asian congeners. Attraction of the 3 Gambrinus species to limoniic acid parallels recent reports of attraction of the congeners G. seminudus (Van Dyke) and G. ursinus (Van Dyke) to this compound, which was originally identified from closely related species of Limonius. Full identifications of additional sex pheromones for elaterid species should provide a more complete picture of the diversities/similarities of the semiochemicals mediating reproductive behaviors of this biologically diverse and taxonomically complex group.

The Sexual Dimorphism in Rectum and Protein Digestion Pathway Influence Sex Pheromone Synthesis in Male Bactrocera Dorsalis

Sexual dimorphism is a crucial aspect of mating and reproduction in many animals, yet the molecular mechanisms remain unclear. In Bactrocera dorsalis, sex pheromones trimethylpyrazine (TMP) and tetramethylpyrazine (TTMP) are specifically synthesized by Bacillus strains in the male rectum. In the female rectum, Bacillus strains are found, but TMP and TTMP are not, indicating sexually dimorphic differences in sex pheromone synthesis. Our anatomical observations and precursor measurements revealed significant differences in rectal structure and ammonium levels between sexes.  In vitro and in vivo experiments reveal that ammonium is vital for sex pheromone synthesis in rectal Bacillus strains. Comparative transcriptome analysis identified ammonium-producing genes (carboxypeptidase B and peptide transporter) in the protein digestion pathway that show much higher expression in the male rectum than in the female rectum. Knocking down the expression of either carboxypeptidase B (or inhibiting enzyme activity) or peptide transporter decreases rectal ammonium levels significantly, resulting in the failure of sex pheromone synthesis in the male rectum. This study provides insights into the presence of sexual dimorphism in internal organs and their functionalities in male-specific sex pheromone synthesis and has significant implications for understanding the molecular mechanisms underlying sex pheromone synthesis by symbionts in insects.

Preparation and indoor virulence determination of a temperature-sensitive insecticide against Zeugodacus cucurbitae (Coquillett)

Zeugodacus cucurbitae (Coquillett) is an important fruit and vegetable pest, especially in high-temperature seasons. In our previous research, we developed a temperature-sensitive sustained-release attractant for Z. cucurbitae, that not only can control the release rate of cuelure according to the temperature change, but also shows an excellent trapping effect on Z. cucurbitae. To further enhance the killing effect of the temperature-sensitive attractant on Z. cucurbitae, this study proposed using it in combination with an insecticide to prepare a temperature-sensitive insecticide for Z. cucurbitae. Based on the controlled release technology of pesticides, a temperature-sensitive Z. cucurbitae insecticide was developed by using PNIPAM gel as a temperature-sensitive switch to carry both cuelure and insecticide at the same time. In addition, the lethal effect of different pesticides on Z. cucurbitae were tested by indoor toxicity test, and the best pesticide combination was screened out. The temperature-sensitive insecticide prepared in this study not only had excellent thermal response and controlled release ability, but also enhanced its toxicological effects on Z. cucurbitae because it contained insecticides. Among them, combining thiamethoxam and clothianidin with the temperature-sensitive attractants was the most effective, and their lethality reached more than 97% against Z. cucurbitae. This study is not only of great practical significance for the monitoring and controlling Z. cucurbitae, but also provides theoretical basis and reference value for the combination of temperature-sensitive attractant and insecticide.

The extraction and identification of active components of the sex pheromones of Asian citrus psyllid, Diaphorina citri

In this study, we extracted and identified the active components of the Asian citrus psyllid, Diaphorina citri sex pheromones to provide a basis for further development of sex attractants. Under laboratory conditions, mating activity in D. citri started 3 d after emergence, which peaked at 6-7 d, and mating activity had no obvious peak during the observed period 7:00-21:00 h. Additionally, D. citri males were attracted to the emanations from conspecific females, especially to the n-hexane extracts of the pheromone. A total of 17 compounds were identified from the n-hexane extracts of female and male D. citri by gas chromatography-mass spectrometer (GC-MS). Among them, 13 compounds were identified from the female D. citri n-hexane extracts, of which 7 (dichloromethane, acetic acid, toluene, butyl acetate, ethyl carbamoylacetate, α-pinene, and 1-nonanal) were not found in the male D. citri n-hexane extracts. In addition, a total of 33 compounds were identified from the solid phase microextraction (SPME) volatiles of the male and female D. citri adults. Among these, 17 compounds were identified from the female D. citri volatiles, of which 6 (cycloheptatriene, 5-methyl-2-phenylindole, 1-dodecanol, cis-11-hexadecena, dodecyl aldehyde, and nerylacetone) were not identified in the volatiles of the D. citri males. It was found that males were significantly attracted to 0.1-10 μL/mL acetic acid and 1-nonanal with the selection rates ranging from 62.04%-70.56% and 62.22%-67.22%, respectively. Therefore, the results of this study suggest that acetic acid and 1-nonanal might be the active compounds of the female D. citri sex pheromones.

Identification of a Female-Produced Sex Attractant Pheromone of the Winter Firefly, Photinus corruscus Linnaeus (Coleoptera: Lampyridae)

Firefly flashes are well-known visual signals used by these insects to find, identify, and choose mates. However, many firefly species have lost the ability to produce light as adults. These "unlighted" species generally lack developed adult light organs, are diurnal rather than nocturnal, and are believed to use volatile pheromones acting over a distance to locate mates. While cuticular hydrocarbons, which may function in mate recognition at close range, have been examined for a handful of the over 2000 extant firefly species, no volatile pheromone has ever been identified. In this study, using coupled gas chromatography - electroantennographic detection, we detected a single female-emitted compound that elicited antennal responses from wild-caught male winter fireflies, Photinus corruscus. The compound was identified as (1S)-exo-3-hydroxycamphor (hydroxycamphor). In field trials at two sites across the species' eastern North American range, large numbers of male P. corruscus were attracted to synthesized hydroxycamphor, verifying its function as a volatile sex attractant pheromone. Males spent more time in contact with lures treated with synthesized hydroxycamphor than those treated with solvent only in laboratory two-choice assays. Further, using single sensillum recordings, we characterized a pheromone-sensitive odorant receptor neuron in a specific olfactory sensillum on male P. corruscus antennae and demonstrated its sensitivity to hydroxycamphor. Thus, this study has identified the first volatile pheromone and its corresponding sensory neuron for any firefly species, and provides a tool for monitoring P. corruscus populations for conservation and further inquiry into the chemical and cellular bases for sexual communication among fireflies.

Identification of the Major Sex Pheromone Component of the Click Beetle Agriotes ferrugineipennis

Synthetic sex pheromone lures are useful tools to monitor and control populations of adult click beetles (Coleoptera: Elateridae). However, sex pheromones for Agriotes click beetle species native to North America have yet to be identified. Here we report the identification and field testing of the sex pheromone of Agriotes ferrugineipennis. Headspace volatiles from female beetles were collected on Porapak Q, and aliquots of Porapak extract were analyzed by gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometry. 7-Methyloctyl 7-methyloctanoate (7Me7Me) emitted by females was more abundant and elicited much stronger responses from male antennae than the aldehydes octanal and nonanal and the ketone 6,10,14-trimethyl-2-pentadecanone. In a field experiment, captures of A. ferrugineipennis males in traps baited with candidate pheromone components exceeded those of unbaited control traps, on average by nearly 1,200 times. Neither the ketone nor the aldehydes as lure constituents appeared to alter captures of males in 7Me7Me-baited traps. We conclude that 7Me7Me is the major, and possibly the only, sex attractant pheromone component of female A. ferrugineipennis.