Masaaki Sawada

Unusual periodicity of sex pheromone production in the large black chaferHolotrichia parallela

Abstract(R)-(−)-Linalool was identified as a minor component sex pheromone of the scarab beetleHolotrichia parallela (Coleoptera: Scarabaeidae). Field evaluations revealed that, although not attractive per se, (R)-(−)-linalool enhances the attractiveness of the major sex pheromone,L-isoleucine methyl ester (LIME). Analyses of the pheromone titers in the glands of field-collected females demonstrated the occurrence of peak levels of 48-hr (“circabidian”) periodicity. The levels of LIME in the glands of 45-day-old virgin females increased over three times from the scototo the photophase of a calling day, but the amounts of (R)-(−)-linalool did not significantly change. Virgin females had in average two times more LIME and 3.6 times more (R)-(−)-linalool than the average amount found in the field-captured beetles throughout the season.

Sex pheromone of oriental beetle,Exomala orientalis: Identification and field evaluation.

A gas chromatograph coupled with a behavioral bioassay was used to identify two sex pheromone components, 7-(Z)- and 7-(E)-tetradecen-2-one of the Oriental beetle (OB),Exomala orientalis. Field experiments showed that the blend of the two isomers (Z:E, 7:1) was not significantly more attractive than theZ component alone. The best performance of traps baited with the synthetic sex pheromone was achieved when they were set with the pheromone device at 30 cm above the ground. Catches in traps baited with 1 and 10 mg were not significantly different, but they were higher (2.9-fold) than captures in traps loaded with 0.1 mg of the pheromone. Further investigations by GC-EAD revealed the presence of a possible minor component, but the small amount of material prevented its identification. 2-(E)-Nonenol, with the same retention time as the natural product, did not affect the attractancy of the synthetic sex pheromone. GC-EAD screening of previously identified sex pheromones of scarab beetles showed that male antennae of the Oriental beetle responded to japonilure, but it showed neither synergism nor inhibition to the OB sex pheromone.

Kairomone from dandelion, Taraxacum officinale, attractant for scarab beetle Anomala octiescostata.

The attraction of the scarab beetleAnomala octiescostata to dandelion,Taraxacum officinale, was demonstrated to be chemically mediated by a mixture ofcis-3-hexenyl acetate, benzaldehyde, phenylacetaldehyde, benzyl alcohol, phenethyl alcohol, phenylacetonitrile, and benzyl benzoate, in the ratio 4:8:14:3:5:19:11. Combination of the synthetic kairomone and sex pheromone (buibuilactone + japonilure, 8:2), significantly increased the total catches ofA. octiescostata. Catches of male (but not female) beetles were significantly higher with the kairomone-pheromone blend than with kairomone alone. The synergistic effect of the kairomone from dandelion on the attractiveness did not significantly differ from that of a food-type lure, anethol, geraniol, and phenethyl propionate (9:0.5:0.5). The latter combined with the synthetic sex pheromone resulted in better attraction of female (but not male)A. octiescostata than the sex pheromone alone.

The scarab beetleAnomala cuprea utilizes the sex pheromone ofPopillia japonica as a minor component

GC-EAD analyses revealed that the scarab beetleAnomala cuprea, the cupreous chafer, utilizes, in addition to the previously identified major sex pheromone (R,Z)-5-(−)-(oct-1-enyl)oxacyclopentan-2-one, a minor component, (R,Z)-5-(−)-(dec-1-enyl)oxacyclopentan-2-one, which has been previously identified as the sex pheromone of the Japanese beetle. Release of the sex pheromone blend did not significantly differ when collected from feeding or starving female beetles, nor did it differ from volatiles collected in the scoto- and photophase. However, after mating, the amount and the ratio of the two components changed. Field tests revealed that traps baited with the synthetic sex pheromone captured more beetles than traps containing only virgin females. Based on field experiments, 10 mg of a 90∶10 blend of the pheromone was suggested as appropriate for monitoring of the cupreous chafer, although the optimal ratio for attractiveness is yet to be established. The occurrence of minor components in the pheromone system of other scarab beetles is also discussed.

Identification and field evaluation ofAnomala octiescostata (Coleoptera: Scarabaeidae) sex pheromone

Using GC-EAD, the sex pheromone of the scarab beetleAnomala octiescostata was identified to be a 8:2 binary mixture of (R,Z)-5-(−)-(oct-1-enyl)oxacyclopentan-2-one and (R,Z)-5-(−)-(dec-1-enyl)oxacyclopentan-2-one. These semiochemicals have been also reported as sex pheromone constituents of otherAnomala species, either geographically or seasonally isolated fromA. octiescostata. Synthetic sex pheromone was highly attractive in the field; 0.1 mg captured significantly more males than two virgin females. Buried traps were significantly more attractive than those positioned at 30, 90, and 150 cm above the ground. In a dose-response test (0.1–100 mg), no saturation due to overdose of pheromone was observed, but in most cases, two dosages differing by 10-fold were not significantly different. Response of males to traps baited with different ratios of the two components was tested in two experiments with randomized blocks and Latin-square designs. Deviation from the natural ratio (8:2) of sex pheromone did not significantly diminish the response of males. Peak flight activity of beetle was recorded at 9:00–10:00 AM JST on sunny days in the end of April 1993.

Scarab beetleAnomala albopilosa albopilosa utilizes a more complex sex pheromone system than a similar speciesA. cuprea.

Four compounds have been identified as sex pheromone constituents of the scarab beetleAnomala albopilosa albopilosa, namely (R, Z)-5-(−)-(oct-1-enyl)oxacyclopentan-2-one (buibuilactone), 2-(E)-nonenol, 2-(E)-nonenal, and methyl benzoate (in the ratio 10:3:3:1). The diel rhythm of pheromone release inA. a. albopilosa showed a peak at the beginning of the scotophase, which is also a peak of mating activity. On the other hand, the similar speciesA. cuprea utilizes a two-constituent sex pheromone, having a common major component, but the pheromone is released both during scoto-and photophase. Temporal difference in mating activity and pheromone release along with chemical diversity seem to form the basis for maintaining species specificity in pheromonal communication betweenA. a. albopilosa andA. cuprea.

Field evaluation ofAnomala schonfeldti ohaus (Coleoptera: Scarabaeidae) synthetic sex pheromone.

Synthetic 2-(E)-nonenol, previously identified as the sex pheromone ofAnomala schonfeldti (Coleoptera: Scarabaeidae), is demonstrated to be very attractive to males in the field. Nevertheless, no significant differences were found between treatments with 1, 5, 10, and 20 mg dosages. Males ofA. schonfeldti were more significantly attracted to traps at 30 cm high than at 90 cm. Although the observed behavior seemed to indicate a trend of more attraction to buried traps than those placed at 30 cm, there was no statistical difference between the two treatments. Pheromone-baited traps caught significantly more beetles than traps containing three virgin females. Over 70% of released beetles were recaptured in six traps surrounding the point of release and separated from each other by 50 m, suggesting a possible use of the pheromone (in combination with floral compounds) in mass trapping.