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Conventional electrochemical methods have major limitations in measuring the kinetics of a heterogeneous electrochemical process such as localized corrosion. One reason for this is that traditional electrochemical kinetic methods are based on the fundamental Butler-Volmer equation 1,2 which only describes the kinetics of a uniform electrode process. Another reason is that traditional electrochemical techniques usually employ a one piece electrode which can only detect mixed or averaged electrochemical parameters over the whole electrode surface and cannot measure electrochemical parameters from a chosen location of the electrode surface. Although techniques such as the scanning reference electrode method and the scanning vibrating electrode method have been developed to detect localized electrochemical parameters in the solution phase, they do not delineate clearly the areas of cathodes and anodes 3 and they do not measure the kinetics of heterogeneous electrochemical processes.In order to measure local electrochemical parameters and to determine the kinetics of a heterogeneous electrochemical process, a wire beam electrode (WBE), 4-11 has been developed. Preliminary applications were in the study of the electrochemical heterogeneity of organic coatings 5,7,8,10 and localized corrosion processes. 4,6,[9][10][11] The WBE is normally fabricated from a bundle of electrically insulated drawn metal wires embedded in insulating material. However it could be prepared by techniques such as machining, casting, laser cutting, electric arc cutting, or electrodeposition. The surface of the WBE usually simulates the surface shape of a practical workpiece under study. Various previous designs and applications of the WBE can be found in Ref. 4-11. The WBE constitutes a unique integrated multielectrode system which effectively simulates a conventional one piece electrode surface. 4,6,10,11 Similar corrosion patterns were experimentally observed over a WBE and a large area one piece electrode surface when both electrodes were exposed to an identical environment. 4,10 The WBE differs from other sectioned electrodes such as the micromosaic platinum electrode, 12,13 the microcomposite glassy carbon electrode, 14,15 the platinum microelectrode array, 16 and other variously designed multielectrode systems 17-21 since these electrode systems, to our knowledge, were not integrated to simulate a heterogeneous electrode surface and were not designed to study heterogeneous electrochemical processes.The WBE is suitable for studying heterogeneous electrochemical processes. First, each wire in a WBE is an individual addressable electrochemical sensor which can measure local electrochemical parameters. Second, the surface area of each wire in an WBE is much smaller than the total working electrode area, thus electrochemical processes on each corroding wire surface can be assumed to be uniform even if the whole electrode surface is electrochemically nonuniform, an approach which is an analogy to calculus principles. 4 This assumption allows ele...

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Trapping of alate aphids at two sites with grease traps over 8 years yielded a total of 51 species, 9 of which flew regularly in high numbers and are referred to as primary species. Six others occasionally occurred in high numbersThe validity of likely inferences from information collected by this method is discussed, as is also the application of the knowledge of flights to problems of aphid control.

SummaryVarious methods of estimating aphid populations are discussed and their limitations are noted.Details are given of the' construction and operation of an electronic counter by means of which normal colonies of aphids can be counted with a repeatability of ± 3%. It is essentially an instrument for use in the laboratory, where a stable power supply is normally available.