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Mode of Action of Carbamate SynergistsThe insecticidal carbamates are synergized by a wide variety of methylenedioxyphenyl compounds. These act as inhibitors of phenolase enzymes which detoxify the carbamates largely by ring hydroxylation. The active inhibitors appear to require a three-point attachment to the phenolase enzyme to orient the methylene carbon so that interaction with a nucleophilic group at the enzyme active site takes place. Tyrosinase, which is

The attraction of male oriental fruit flies to methyl eugenol and 34 analogues was investigated quantitatively using the characteristic feeding response. Methyl eugenol was the most active compound studied, with a feeding response to 0.01 Ag, but saturation of the allyl side chain or rep acement of allyl by allyloxy produced compounds almost as effective. Replacement of the methoxy groups by methylenedioxy, methyl, or chloro groups abolished all response. The ring geometry of the methoxy groups was critical, with orthodimethoxy most active and meta-dimethoxy inactive. Replacement of methoxy with hydroxy, methylthio, or amino groups did not abolish the response. The failure of the oriental fruit fly to respond to the methyl and chloro isosteres of methyl eugenol was contrasted with the response of a human odor panel which perceived these compounds as having weak floral odors.

Male oriental fruit flies (Dacus dorsalis) from colonies in Taiwan and Hawaii were evaluated for limit of response to various analogues of methyl eugenol. The results are interpreted in terms of the geometry and allosteric requirements of the antennal receptor that triggers the characteristic methyl eugenol reflex. This receptor has evolved for complementarity to all portions of the methyl eugenol molecule and responds only to ortho-substituted benzenes with adjacent oxygen atoms or isoelectronic equivalents. Substantial differences in responses of Taiwan and Hawaiian D. dorsalis suggest that perceptible evolution of the receptor protein has occurred during the past 50 years. A plausible scheme for the coevolution of dacini Flies with plants containing phenylpropionoid essential oils is outlined.When exposed to nanogram quantities of 3,4-dimethoxyallylbenzene (methyl eugenol), a widely distributed phenylpropionoid essential oil, the male oriental fruit fly Dacus dorsalis Hendel undergoes a characteristic sequential response of searching with pulsating mouthparts, arrest, and compulsive feeding (1). This sensitive behavioral response to a simple chemical provides a useful tool for investigations of the physicochemical interactions between kairomone and antennal receptor, of the neurological complexities of insect behavior, and of the coevolution of a large and rapidly evolving family of Diptera (Tephritidae) with various plant families. Previously (1) we concluded that the depolarization of the olfactory sensillum resulted from a conformational change in the lipoprotein receptor involving the unshared electron pairs of the orthodimethoxybenzene moiety. In the present investigation, we have extended the mapping of the active site of the methyl eugenol receptor to evaluation of the optimal size and shape of the lipoprotein patch that is complementary in structure to the methyl eugenol molecule. We have also begun the exploration of coevolutionary development of Dacinae flies with phenylpropionoid essential oils, comparing responses of D. dorsalis in Taiwan and Hawaii.METHODS AND MATERIALS Attractancy of methyl eugenol and related chemicals was measured as described (1). Aliquots of liquid attractants were applied by microliter disposable pipettes to the center of 9-cm Whatman no. 1 filter paper discs. Dilutions of crystalline compounds or amounts of liquids below the microliter range were prepared in reagent grade acetone and applied to the test paper by microliter pipette. The filter paper discs were placed on squares of aluminum foil with the corners folded over the filter paper to prevent the fruit flies from contacting the underside of the test paper. The treated filter paper discs were placed on the floor of 30-cm3 (1 ft3) aluminum-screen cages containing approximately 100 male laboratory-reared D. dorsalis age 12-20 days beyond eclosion. At 1, 2, 5, 10, and 20 min after introduction of the test paper, the number of male flies attracted to the treated area was recorded and observations were made of th...