Electrophysiological and behavioral activity of secondary metabolites in the confused flour beetle, Tribolium confusum.

Several previous studies have addressed pheromone communication in various flour beetles (Coleoptera: Tenebrionidae), including the confused flour beetle, Tribolium confusum (du Val). Different stereoisomers of 4,8-dimethyldecanal (DMD) were reported as the only components of an aggregation pheromone, but the behavioral activity of DMD is low. In the present study, additional previously reported secondary metabolites (benzoquinones and hydrocarbons) were tested for electrophysiological activity (EAG) with both sexes of T. confusum. Two benzoquinones and three monoenic hydrocarbons elicited significant EAG activity from both male and female antennae. There was an elevated male EAG response (vs. the females) to two out of the three hydrocarbons and for both quinones. The EAG-active compounds were subsequently investigated for behavioral activity in a walking bioassay. Benzoquinones are considered toxic and have been assigned a function as alarm substances in flour beetles, but we found that methyl-1, 4-benzoquinone in intermediate concentrations was attractive to both male and female beetles and could therefore act as an aggregation pheromone component. Males were also attracted to ethyl-1,4-benzoquinone. The corresponding hydroquinones, presumed precursors of the benzoquinones, did not elicit any electrophysiological response and were not tested for behavioral activity. The unsaturated hydrocarbons (1-tetradecene, 1-pentadecene, and 1-hexadecene) elicited significant EAG responses from both male and female antennae and were also attractive in the behavioral assay. Our results show that several beetle-produced compounds, in addition to 4,8-dimethyldecanal, may be part of a complex pheromone system in flour beetles and play a role in mediating aggregation in T. confusum.

Release rates for pine sawfly pheromones from two types of dispensers and phenology of Neodiprion sertifer.

Comparisons of release rates, duration in the field, and catch efficiency of polyethylene and cotton roll dispensers for the sex pheromones of sawflies (Hymenoptera: Diprionidae) were conducted. The release rates of the Neodiprion sertifer (Geoffr.) and Diprion pini (L.) sex pheromones, the acetates of pentadecanol and (2S,3S,7S)-3,7-dimethyl (2S,3R,7R)-3,7-dimethyl-2-tridecanol from polyethylene dispensers were measured at different temperatures in the laboratory. The release rates for the substances depended on both the temperature and initial load in the vials. The catch from cotton rolls baited with 100 micrograms of the acetate or propionate of 3,7-dimethyl-2-pentadecanol was compared to the catch from regularly renewed cotton rolls baited with 10 micrograms of the same acetate. The catch was higher for the 100-microgram cotton rolls for, at most, 45 days, and there was no significant differences in catch between the acetate and the propionate. The catch in traps baited with polyethylene or cotton roll dispensers loaded with the acetate of 3,7-dimethyl-2-pentadecanol was compared and showed that cotton roll traps mirrored the decreasing release of the substance rather than the actual flight activity. The length of the flight period of N. sertifer in Sweden, the Czech Republic, Italy, and Greece did not exceed 100 days in any of the countries. By adjusting the initial pheromone load of the polyethylene vials to the expected temperatures, it should be possible to get a constant and sufficiently high release rate during the entire flight period.

Sex pheromone of the pine sawfly Macrodiprion nemoralis (Hymenoptera:Diprionidae): identification of (2S,3R,7R,9S)-3,7, 9-trimethyl-2-tridecanol as the precursor for the active pheromone acetate.

The main component of the sex pheromone precursor in females of Macrodiprion nemoralis was identified as a threo-3,7, 9-trimethyl-2-tridecanol isomer, approximately 800 pg per female, by gas chromatography-mass spectrometry. Comparison of mass spectrometric ion chromatograms showed that the natural compound in the female extract has the same retention time and mass spectrum as one of the two synthetic threo peaks. The acetate of the synthetic 16-isomer mixture caught a large number of males in the field, confirming the structure of the active pheromone. Comparison of gas chromatograms of the natural female extract with the eight synthetic threo stereoisomers showed that the pheromone is the (2S,3R,7R, 9S)-stereoisomer of 3,7,9-trimethyl-2-tridecyl acetate.

Species-specific, two-component, volatile signals in two sympatric ant-lion species:Synclysis baetica andAcanthaclisis occitanica (Neuroptera, Myrmeleontidae).

The thoracic glands of males in two ant-lion speciesSynclysis baetica andAcanthaclisis occitanica, which occur sympatrically in Israel, were found to contain a volatile secretion with two-component blends of nerol oxide and (R,Z)-6-tridecen-2-ol (approx 1∶5) and nerol oxide and 10-homonerol oxide (approx. 1∶2), respectively. Chemical analyses were performed using gas chromatography-mass spectrometry, chiral gas chromatography, and ozonolysis, and the proposed structures were confirmed by synthesis. The species-specific, few-component volatile signals are thought to function as a reproductive isolation mechanism between the two sympatric species. Biochemical relationships between the nerol derivatives and between the unsaturated secondary alcohols are discussed.

Sex pheromone perception in male pine sawflies, Neodiprion sertifer (Hymenoptera; Diprionidae).

Electroantennographic and single sensillum recordings were performed on male pine sawfly, Neodiprion sertifer, antennae. Responses to the sex pheromone component (2S, 3S, 7S)- 3,7-dimethyl-2-pentadecenyl (diprionyl) acetate (SSS:OAc), to the behavioral inhibitor (2S, 3R, 7R)-diprionyl acetate (SRR:OAc), to the six other enantiomers of diprionyl acetate, and to the biosynthetic precursor diprionol were recorded. Responses to trans-perillenal, a monoterpene identified in female gland extracts and to (2S, 3S, 7S)-diprionyl propionate (SSS:OPr), a field attractant for N. sertifer and some related sawfly species were also recorded. EAG recordings demonstrated a high antennal sensitivity to SSS:OAc and to SSS:OPr. A somewhat lower response was elicited by SRR:OAc. Single sensillum recordings revealed 8-12 different cells firing in each sensillum, corresponding to the number of cells observed in earlier morphological investigations. Out of these cells all, except one, responded to SSS:OAc and to SSS:OPr. No differences in the response to the two components could be observed. The largest amplitude cell in each sensillum was specifically tuned to the behavioral antagonist, SRR:OAc. The pheromone perception system encountered in male pine sawflies thus differs clearly from that observed in moths.

Structures, absolute configurations, and syntheses of volatile signals from three sympatric ant-lion species,Euroleon nostras, Grocus bore, andMyrmeleon formicarius (Neuroptera: Myrmeleontidae).

The thoracic gland of the ant-lionEuroleon nostras was found to contain nerol oxide (1a) and (Z)-6-undecen-2-ol (nostrenol,3) while the speciesGrocus bore contained 10-homonerol oxide (1b) and nostrenol (3). Nerol (2a) and 10-homonerol (2b) were found in a third species,Myrmeleon formicarius. 10-Homonerol, racemic 10-homonerol oxide, and racemic as well as (R)- and (S)-nostrenol were synthesized. The nerol oxide ofE. nostras and the 10-homonerol oxide ofG. bore were found to be racemic, while both species contained optically pure (R)-nostrenol (28).

Structure-activity studies on aggregation pheromone components ofPityogenes chalcographus (Coleoptera: Scolytidae) : All stereoisomers of chalcogran and methyl 2,4-decadienoate.

Syntheses of all four Stereoisomers (2S,5S; 2S,5R;2R,5R; and2R,5S) of chalcogran, a major component of the aggregation pheromone ofPityogenes chalcographus, and of all four isomers (2Z,4Z; 2Z,4E; 2E,4E; and 2E,4Z) of methyl 2,4-decadienoate (MD), the second major pheromone component, are briefly described. Attraction responses of walking beetles of both sexes were tested to mixtures of the synergistic pheromone components or analogs. These bioassays showed that theE,Z isomer of MD is the most active when tested with chalcogran. When tested with (E,Z)-MD, (2S,5R)-chalcogran was the most active stereoisomer, while 2R,5R and 2R,5S isomers had intermediate activities, and the 2S,5S isomer was inactive. There was no evidence that the relatively less active Stereoisomers of chalcogran inhibited or promoted attraction to (2S,5R)-chalcogran with (E,Z)-MD. Male beetles only produce the activeE,Z isomer of MD (inactive alone) and their hindguts contain the most active (2S,5R)- and least active (2S,5S)-chalcogran. A mixture of all MD isomers with racemic chalcogran was not significantly different in attractivity compared to (E,Z)-MD with racemic chalcogran, indicating no synergistic or inhibitory effects of the inactive isomers of MD.